PROC(5)



PROC(5)                    Linux Programmer's Manual                   PROC(5)

NAME
       proc - process information pseudo-filesystem

DESCRIPTION
       The  proc filesystem is a pseudo-filesystem which provides an interface
       to kernel data structures.  It is commonly  mounted  at  /proc.   Typi-
       cally,  it  is  mounted automatically by the system, but it can also be
       mounted manually using a command such as:

           mount -t proc proc /proc

       Most of the files in the proc filesystem are read-only, but some  files
       are writable, allowing kernel variables to be changed.

   Mount options
       The proc filesystem supports the following mount options:

       hidepid=n (since Linux 3.3)
              This   option   controls  who  can  access  the  information  in
              /proc/[pid] directories.  The argument, n, is one of the follow-
              ing values:

              0   Everybody  may  access all /proc/[pid] directories.  This is
                  the traditional behavior, and  the  default  if  this  mount
                  option is not specified.

              1   Users  may  not  access  files and subdirectories inside any
                  /proc/[pid]  directories  but  their  own  (the  /proc/[pid]
                  directories  themselves  remain  visible).   Sensitive files
                  such as /proc/[pid]/cmdline and /proc/[pid]/status  are  now
                  protected  against other users.  This makes it impossible to
                  learn whether any user is running  a  specific  program  (so
                  long  as  the program doesn't otherwise reveal itself by its
                  behavior).

              2   As for mode 1, but in addition the  /proc/[pid]  directories
                  belonging  to other users become invisible.  This means that
                  /proc/[pid] entries can no longer be used  to  discover  the
                  PIDs  on  the  system.   This  doesn't  hide the fact that a
                  process with a specific PID value exists (it can be  learned
                  by  other  means,  for  example,  by "kill -0 $PID"), but it
                  hides a process's UID and  GID,  which  could  otherwise  be
                  learned  by  employing  stat(2)  on a /proc/[pid] directory.
                  This greatly complicates an  attacker's  task  of  gathering
                  information   about  running  processes  (e.g.,  discovering
                  whether some daemon is  running  with  elevated  privileges,
                  whether  another  user  is  running  some sensitive program,
                  whether other users are running any program at all,  and  so
                  on).

       gid=gid (since Linux 3.3)
              Specifies  the  ID  of  a  group whose members are authorized to
              learn process information otherwise prohibited by hidepid (i.e.,
              users  in  this  group  behave  as though /proc was mounted with
              hidepid=0).  This group should be  used  instead  of  approaches
              such as putting nonroot users into the sudoers(5) file.

   Files and directories
       The  following  list  describes many of the files and directories under
       the /proc hierarchy.

       /proc/[pid]
              There is a numerical subdirectory for each running process;  the
              subdirectory is named by the process ID.

              Each  /proc/[pid]  subdirectory  contains  the  pseudo-files and
              directories described below.  These files are normally owned  by
              the  effective user and effective group ID of the process.  How-
              ever, as a security measure, the ownership is made root:root  if
              the  process's "dumpable" attribute is set to a value other than
              1.  This attribute may change for the following reasons:

              *  The  attribute  was   explicitly   set   via   the   prctl(2)
                 PR_SET_DUMPABLE operation.

              *  The   attribute   was   reset   to  the  value  in  the  file
                 /proc/sys/fs/suid_dumpable (described below), for the reasons
                 described in prctl(2).

              Resetting the "dumpable" attribute to 1 reverts the ownership of
              the /proc/[pid]/* files to the process's real UID and real GID.

       /proc/[pid]/attr
              The files in this directory provide an API for security modules.
              The  contents  of  this directory are files that can be read and
              written in  order  to  set  security-related  attributes.   This
              directory  was  added  to support SELinux, but the intention was
              that the API be general enough to support  other  security  mod-
              ules.   For  the purpose of explanation, examples of how SELinux
              uses these files are provided below.

              This directory is present only if the kernel was configured with
              CONFIG_SECURITY.

       /proc/[pid]/attr/current (since Linux 2.6.0)
              The  contents  of  this  file  represent  the  current  security
              attributes of the process.

              In SELinux, this file is used to get the security context  of  a
              process.   Prior to Linux 2.6.11, this file could not be used to
              set the security context (a  write  was  always  denied),  since
              SELinux  limited  process security transitions to execve(2) (see
              the description of /proc/[pid]/attr/exec, below).   Since  Linux
              2.6.11,  SELinux  lifted  this  restriction and began supporting
              "set" operations via writes to this node if authorized  by  pol-
              icy,  although use of this operation is only suitable for appli-
              cations that are trusted  to  maintain  any  desired  separation
              between  the  old  and  new  security  contexts.  Prior to Linux
              2.6.28, SELinux did not allow threads  within  a  multi-threaded
              process  to set their security context via this node as it would
              yield an  inconsistency  among  the  security  contexts  of  the
              threads  sharing  the  same  memory  space.  Since Linux 2.6.28,
              SELinux lifted this restriction and began supporting "set" oper-
              ations  for  threads  within  a multithreaded process if the new
              security context is bounded by the old security  context,  where
              the  bounded  relation  is defined in policy and guarantees that
              the new security context has a subset of the permissions of  the
              old security context.  Other security modules may choose to sup-
              port "set" operations via writes to this node.

       /proc/[pid]/attr/exec (since Linux 2.6.0)
              This file represents the attributes to  assign  to  the  process
              upon a subsequent execve(2).

              In  SELinux,  this is needed to support role/domain transitions,
              and execve(2) is the preferred point to  make  such  transitions
              because  it offers better control over the initialization of the
              process in the new security label and the inheritance of  state.
              In SELinux, this attribute is reset on execve(2) so that the new
              program reverts to the default behavior for any execve(2)  calls
              that  it  may  make.  In SELinux, a process can set only its own
              /proc/[pid]/attr/exec attribute.

       /proc/[pid]/attr/fscreate (since Linux 2.6.0)
              This file represents the attributes to assign to  files  created
              by  subsequent  calls  to  open(2),  mkdir(2),  symlink(2),  and
              mknod(2)

              SELinux employs this file to support creation of a  file  (using
              the  aforementioned  system  calls)  in  a secure state, so that
              there is no risk of inappropriate access being obtained  between
              the  time  of creation and the time that attributes are set.  In
              SELinux, this attribute is reset on execve(2), so that  the  new
              program  reverts  to  the default behavior for any file creation
              calls it may make, but the attribute will persist across  multi-
              ple file creation calls within a program unless it is explicitly
              reset.   In  SELinux,  a  process   can   set   only   its   own
              /proc/[pid]/attr/fscreate attribute.

       /proc/[pid]/attr/keycreate (since Linux 2.6.18)
              If  a process writes a security context into this file, all sub-
              sequently created keys (add_key(2)) will be  labeled  with  this
              context.   For  further  information, see the kernel source file
              Documentation/security/keys/core.rst   (or    file    Documenta-
              tion/security/keys.txt  on  Linux between 3.0 and 4.13, or Docu-
              mentation/keys.txt before Linux 3.0).

       /proc/[pid]/attr/prev (since Linux 2.6.0)
              This file contains the security context of  the  process  before
              the   last   execve(2);   that   is,   the   previous  value  of
              /proc/[pid]/attr/current.

       /proc/[pid]/attr/socketcreate (since Linux 2.6.18)
              If a process writes a security context into this file, all  sub-
              sequently created sockets will be labeled with this context.

       /proc/[pid]/autogroup (since Linux 2.6.38)
              See sched(7).

       /proc/[pid]/auxv (since 2.6.0-test7)
              This  contains  the  contents of the ELF interpreter information
              passed to the process at exec time.  The format is one  unsigned
              long  ID  plus one unsigned long value for each entry.  The last
              entry contains two zeros.  See also getauxval(3).

              Permission to access this file is governed by  a  ptrace  access
              mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/cgroup (since Linux 2.6.24)
              See cgroups(7).

       /proc/[pid]/clear_refs (since Linux 2.6.22)

              This  is  a  write-only  file,  writable  only  by  owner of the
              process.

              The following values may be written to the file:

              1 (since Linux 2.6.22)
                     Reset the PG_Referenced and ACCESSED/YOUNG bits  for  all
                     the  pages  associated  with the process.  (Before kernel
                     2.6.32, writing any nonzero value to this file  had  this
                     effect.)

              2 (since Linux 2.6.32)
                     Reset  the  PG_Referenced and ACCESSED/YOUNG bits for all
                     anonymous pages associated with the process.

              3 (since Linux 2.6.32)
                     Reset the PG_Referenced and ACCESSED/YOUNG bits  for  all
                     file-mapped pages associated with the process.

              Clearing  the  PG_Referenced  and ACCESSED/YOUNG bits provides a
              method to measure approximately how much  memory  a  process  is
              using.  One first inspects the values in the "Referenced" fields
              for the VMAs shown in /proc/[pid]/smaps to get an  idea  of  the
              memory  footprint of the process.  One then clears the PG_Refer-
              enced and ACCESSED/YOUNG bits  and,  after  some  measured  time
              interval,  once  again  inspects  the values in the "Referenced"
              fields to get an idea of the change in memory footprint  of  the
              process during the measured interval.  If one is interested only
              in inspecting the selected mapping types, then the value 2 or  3
              can be used instead of 1.

              Further values can be written to affect different properties:

              4 (since Linux 3.11)
                     Clear  the  soft-dirty  bit  for all the pages associated
                     with the process.  This  is  used  (in  conjunction  with
                     /proc/[pid]/pagemap) by the check-point restore system to
                     discover which pages of a process have been dirtied since
                     the file /proc/[pid]/clear_refs was written to.

              5 (since Linux 4.0)
                     Reset  the  peak resident set size ("high water mark") to
                     the process's current resident set size value.

              Writing any value to  /proc/[pid]/clear_refs  other  than  those
              listed above has no effect.

              The  /proc/[pid]/clear_refs  file  is  present  only if the CON-
              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/[pid]/cmdline
              This read-only file holds the  complete  command  line  for  the
              process,  unless  the  process is a zombie.  In the latter case,
              there is nothing in this file: that is, a read on this file will
              return  0 characters.  The command-line arguments appear in this
              file as a set of strings separated by null bytes ('\0'), with  a
              further null byte after the last string.

       /proc/[pid]/comm (since Linux 2.6.33)
              This file exposes the process's comm value--that is, the command
              name associated with the process.  Different threads in the same
              process   may   have   different  comm  values,  accessible  via
              /proc/[pid]/task/[tid]/comm.   A  thread  may  modify  its  comm
              value,  or  that of any of other thread in the same thread group
              (see the discussion of CLONE_THREAD in clone(2)), by writing  to
              the   file   /proc/self/task/[tid]/comm.   Strings  longer  than
              TASK_COMM_LEN (16) characters are silently truncated.

              This file provides a superset of the  prctl(2)  PR_SET_NAME  and
              PR_GET_NAME operations, and is employed by pthread_setname_np(3)
              when used to rename threads other than the caller.

       /proc/[pid]/coredump_filter (since Linux 2.6.23)
              See core(5).

       /proc/[pid]/cpuset (since Linux 2.6.12)
              See cpuset(7).

       /proc/[pid]/cwd
              This is a symbolic link to the current working directory of  the
              process.   To  find out the current working directory of process
              20, for instance, you can do this:

                  $ cd /proc/20/cwd; /bin/pwd

              Note that the pwd command is often a shell built-in,  and  might
              not work properly.  In bash(1), you may use pwd -P.

              In  a  multithreaded process, the contents of this symbolic link
              are not available if the  main  thread  has  already  terminated
              (typically by calling pthread_exit(3)).

              Permission  to  dereference  or read (readlink(2)) this symbolic
              link    is    governed    by    a     ptrace     access     mode
              PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/environ
              This file contains the initial environment that was set when the
              currently executing program  was  started  via  execve(2).   The
              entries  are  separated by null bytes ('\0'), and there may be a
              null byte at the end.  Thus, to print  out  the  environment  of
              process 1, you would do:

                  $ strings /proc/1/environ

              If,  after  an  execve(2),  the process modifies its environment
              (e.g., by calling functions such as putenv(3) or  modifying  the
              environ(7)  variable directly), this file will not reflect those
              changes.

              Furthermore, a process may change the memory location that  this
              file refers via prctl(2) operations such as PR_SET_MM_ENV_START.

              Permission  to  access  this file is governed by a ptrace access
              mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/exe
              Under Linux 2.2 and later, this file is a symbolic link contain-
              ing  the actual pathname of the executed command.  This symbolic
              link can be dereferenced normally; attempting to  open  it  will
              open  the  executable.  You can even type /proc/[pid]/exe to run
              another copy of the same executable that is being run by process
              [pid].   If  the  pathname  has been unlinked, the symbolic link
              will contain the string '(deleted)'  appended  to  the  original
              pathname.  In a multithreaded process, the contents of this sym-
              bolic link are not available if the main thread has already ter-
              minated (typically by calling pthread_exit(3)).

              Permission  to  dereference  or read (readlink(2)) this symbolic
              link    is    governed    by    a     ptrace     access     mode
              PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

              Under Linux 2.0 and earlier, /proc/[pid]/exe is a pointer to the
              binary which was executed, and appears as a  symbolic  link.   A
              readlink(2)  call  on this file under Linux 2.0 returns a string
              in the format:

                  [device]:inode

              For example, [0301]:1502 would be inode 1502 on device major  03
              (IDE,  MFM,  etc. drives) minor 01 (first partition on the first
              drive).

              find(1) with the -inum option can be used to locate the file.

       /proc/[pid]/fd/
              This is a subdirectory containing one entry for each file  which
              the process has open, named by its file descriptor, and which is
              a symbolic link to the actual file.  Thus, 0 is standard  input,
              1 standard output, 2 standard error, and so on.

              For  file descriptors for pipes and sockets, the entries will be
              symbolic links whose content is the file type with the inode.  A
              readlink(2) call on this file returns a string in the format:

                  type:[inode]

              For  example, socket:[2248868] will be a socket and its inode is
              2248868.  For sockets, that inode  can  be  used  to  find  more
              information in one of the files under /proc/net/.

              For  file  descriptors  that  have no corresponding inode (e.g.,
              file   descriptors   produced   by   bpf(2),    epoll_create(2),
              eventfd(2),  inotify_init(2),  perf_event_open(2),  signalfd(2),
              timerfd_create(2), and userfaultfd(2)), the entry will be a sym-
              bolic link with contents of the form

                  anon_inode:<file-type>

              In  many  cases  (but  not  all), the file-type is surrounded by
              square brackets.

              For example, an epoll file descriptor will have a symbolic  link
              whose content is the string anon_inode:[eventpoll].

              In  a  multithreaded process, the contents of this directory are
              not available if the main thread has already  terminated  (typi-
              cally by calling pthread_exit(3)).

              Programs  that  take  a filename as a command-line argument, but
              don't take input from standard input if no argument is supplied,
              and  programs that write to a file named as a command-line argu-
              ment, but don't send their output to standard output if no argu-
              ment is supplied, can nevertheless be made to use standard input
              or standard output by using /proc/[pid]/fd files as command-line
              arguments.   For example, assuming that -i is the flag designat-
              ing an input file and -o is the flag designating an output file:

                  $ foobar -i /proc/self/fd/0 -o /proc/self/fd/1 ...

              and you have a working filter.

              /proc/self/fd/N is approximately the same as /dev/fd/N  in  some
              UNIX and UNIX-like systems.  Most Linux MAKEDEV scripts symboli-
              cally link /dev/fd to /proc/self/fd, in fact.

              Most systems provide symbolic links /dev/stdin, /dev/stdout, and
              /dev/stderr, which respectively link to the files 0, 1, and 2 in
              /proc/self/fd.  Thus the example command above could be  written
              as:

           $ foobar -i /dev/stdin -o /dev/stdout ...

              Permission  to  dereference  or  read (readlink(2)) the symbolic
              links in this directory is governed  by  a  ptrace  access  mode
              PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/fdinfo/ (since Linux 2.6.22)
              This  is a subdirectory containing one entry for each file which
              the process has open, named by its file descriptor.   The  files
              in this directory are readable only by the owner of the process.
              The contents of each file can  be  read  to  obtain  information
              about the corresponding file descriptor.  The content depends on
              the type of file referred to by the corresponding file  descrip-
              tor.

              For regular files and directories, we see something like:

                  $ cat /proc/12015/fdinfo/4
                  pos:    1000
                  flags:  01002002
                  mnt_id: 21

              The fields are as follows:

              pos    This is a decimal number showing the file offset.

              flags  This  is  an  octal  number that displays the file access
                     mode and file status flags (see open(2)).  If the  close-
                     on-exec file descriptor flag is set, then flags will also
                     include the value O_CLOEXEC.

                     Before Linux 3.1, this field  incorrectly  displayed  the
                     setting  of  O_CLOEXEC  at  the time the file was opened,
                     rather than the  current  setting  of  the  close-on-exec
                     flag.

              mnt_id This  field,  present  since Linux 3.15, is the ID of the
                     mount point containing this file.  See the description of
                     /proc/[pid]/mountinfo.

              For  eventfd  file  descriptors  (see eventfd(2)), we see (since
              Linux 3.8) the following fields:

                  pos: 0
                  flags:    02
                  mnt_id:   10
                  eventfd-count:               40

              eventfd-count is the current value of the  eventfd  counter,  in
              hexadecimal.

              For  epoll  file descriptors (see epoll(7)), we see (since Linux
              3.8) the following fields:

                  pos: 0
                  flags:    02
                  mnt_id:   10
                  tfd:        9 events:       19 data: 74253d2500000009
                  tfd:        7 events:       19 data: 74253d2500000007

              Each of the lines  beginning  tfd  describes  one  of  the  file
              descriptors  being  monitored via the epoll file descriptor (see
              epoll_ctl(2) for some details).  The tfd field is the number  of
              the  file descriptor.  The events field is a hexadecimal mask of
              the events being monitored for this file descriptor.   The  data
              field is the data value associated with this file descriptor.

              For  signalfd  file descriptors (see signalfd(2)), we see (since
              Linux 3.8) the following fields:

                  pos: 0
                  flags:    02
                  mnt_id:   10
                  sigmask:  0000000000000006

              sigmask is the hexadecimal mask of signals that are accepted via
              this  signalfd  file descriptor.  (In this example, bits 2 and 3
              are set, corresponding to the signals SIGINT  and  SIGQUIT;  see
              signal(7).)

              For  inotify  file  descriptors  (see inotify(7)), we see (since
              Linux 3.8) the following fields:

                  pos: 0
                  flags:    00
                  mnt_id:   11
                  inotify wd:2 ino:7ef82a sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:2af87e00220ffd73
                  inotify wd:1 ino:192627 sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:27261900802dfd73

              Each of the lines beginning with "inotify" displays  information
              about one file or directory that is being monitored.  The fields
              in this line are as follows:

              wd     A watch descriptor number (in decimal).

              ino    The inode number of the target file (in hexadecimal).

              sdev   The ID of the device where the target  file  resides  (in
                     hexadecimal).

              mask   The  mask  of  events being monitored for the target file
                     (in hexadecimal).

              If the kernel was built with exportfs support, the path  to  the
              target  file  is exposed as a file handle, via three hexadecimal
              fields: fhandle-bytes, fhandle-type, and f_handle.

              For fanotify file descriptors (see fanotify(7)), we  see  (since
              Linux 3.8) the following fields:

                  pos: 0
                  flags:    02
                  mnt_id:   11
                  fanotify flags:0 event-flags:88002
                  fanotify ino:19264f sdev:800001 mflags:0 mask:1 ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:4f261900a82dfd73

              The  fourth  line displays information defined when the fanotify
              group was created via fanotify_init(2):

              flags  The flags argument given to  fanotify_init(2)  (expressed
                     in hexadecimal).

              event-flags
                     The  event_f_flags  argument  given  to  fanotify_init(2)
                     (expressed in hexadecimal).

              Each additional line shown  in  the  file  contains  information
              about  one  of  the  marks in the fanotify group.  Most of these
              fields are as for inotify, except:

              mflags The flags associated with the mark (expressed in hexadec-
                     imal).

              mask   The events mask for this mark (expressed in hexadecimal).

              ignored_mask
                     The  mask  of  events  that  are  ignored  for  this mark
                     (expressed in hexadecimal).

              For details on these fields, see fanotify_mark(2).

       /proc/[pid]/gid_map (since Linux 3.5)
              See user_namespaces(7).

       /proc/[pid]/io (since kernel 2.6.20)
              This file contains I/O statistics for the process, for example:

                  # cat /proc/3828/io
                  rchar: 323934931
                  wchar: 323929600
                  syscr: 632687
                  syscw: 632675
                  read_bytes: 0
                  write_bytes: 323932160
                  cancelled_write_bytes: 0

              The fields are as follows:

              rchar: characters read
                     The number of bytes which this task has caused to be read
                     from storage.  This is simply the sum of bytes which this
                     process passed to read(2) and similar system  calls.   It
                     includes things such as terminal I/O and is unaffected by
                     whether or not actual physical disk I/O was required (the
                     read might have been satisfied from pagecache).

              wchar: characters written
                     The  number of bytes which this task has caused, or shall
                     cause to be written to disk.  Similar caveats apply  here
                     as with rchar.

              syscr: read syscalls
                     Attempt  to count the number of read I/O operations--that
                     is, system calls such as read(2) and pread(2).

              syscw: write syscalls
                     Attempt to count the number of write I/O operations--that
                     is, system calls such as write(2) and pwrite(2).

              read_bytes: bytes read
                     Attempt  to  count the number of bytes which this process
                     really did cause to be fetched from  the  storage  layer.
                     This is accurate for block-backed filesystems.

              write_bytes: bytes written
                     Attempt  to  count the number of bytes which this process
                     caused to be sent to the storage layer.

              cancelled_write_bytes:
                     The big inaccuracy here is truncate.  If a process writes
                     1MB  to a file and then deletes the file, it will in fact
                     perform no writeout.  But it will have been accounted  as
                     having  caused  1MB of write.  In other words: this field
                     represents the number of bytes which this process  caused
                     to not happen, by truncating pagecache.  A task can cause
                     "negative" I/O too.  If this task  truncates  some  dirty
                     pagecache, some I/O which another task has been accounted
                     for (in its write_bytes) will not be happening.

              Note: In the current implementation, things are a  bit  racy  on
              32-bit  systems:  if  process A reads process B's /proc/[pid]/io
              while process B  is  updating  one  of  these  64-bit  counters,
              process A could see an intermediate result.

              Permission  to  access  this file is governed by a ptrace access
              mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/limits (since Linux 2.6.24)
              This file displays the soft limit, hard limit, and units of mea-
              surement  for  each  of the process's resource limits (see getr-
              limit(2)).  Up to and including Linux 2.6.35, this file is  pro-
              tected  to  allow  reading  only by the real UID of the process.
              Since Linux 2.6.36, this file is readable by all  users  on  the
              system.

       /proc/[pid]/map_files/ (since kernel 3.3)
              This  subdirectory  contains  entries  corresponding  to memory-
              mapped files (see mmap(2)).  Entries are named by memory  region
              start  and  end address pair (expressed as hexadecimal numbers),
              and are symbolic links to the mapped files themselves.  Here  is
              an example, with the output wrapped and reformatted to fit on an
              80-column display:

                  # ls -l /proc/self/map_files/
                  lr--------. 1 root root 64 Apr 16 21:31
                              3252e00000-3252e20000 -> /usr/lib64/ld-2.15.so
                  ...

              Although these entries are present for memory regions that  were
              mapped  with  the MAP_FILE flag, the way anonymous shared memory
              (regions created with the MAP_ANON | MAP_SHARED flags) is imple-
              mented  in  Linux  means  that  such regions also appear on this
              directory.  Here is an example where  the  target  file  is  the
              deleted /dev/zero one:

                  lrw-------. 1 root root 64 Apr 16 21:33
                              7fc075d2f000-7fc075e6f000 -> /dev/zero (deleted)

              This  directory  appears  only  if the CONFIG_CHECKPOINT_RESTORE
              kernel   configuration    option    is    enabled.     Privilege
              (CAP_SYS_ADMIN)  is required to view the contents of this direc-
              tory.

       /proc/[pid]/maps
              A file containing the currently mapped memory regions and  their
              access  permissions.   See  mmap(2) for some further information
              about memory mappings.

              Permission to access this file is governed by  a  ptrace  access
              mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

              The format of the file is:

    address           perms offset  dev   inode       pathname
    00400000-00452000 r-xp 00000000 08:02 173521      /usr/bin/dbus-daemon
    00651000-00652000 r--p 00051000 08:02 173521      /usr/bin/dbus-daemon
    00652000-00655000 rw-p 00052000 08:02 173521      /usr/bin/dbus-daemon
    00e03000-00e24000 rw-p 00000000 00:00 0           [heap]
    00e24000-011f7000 rw-p 00000000 00:00 0           [heap]
    ...
    35b1800000-35b1820000 r-xp 00000000 08:02 135522  /usr/lib64/ld-2.15.so
    35b1a1f000-35b1a20000 r--p 0001f000 08:02 135522  /usr/lib64/ld-2.15.so
    35b1a20000-35b1a21000 rw-p 00020000 08:02 135522  /usr/lib64/ld-2.15.so
    35b1a21000-35b1a22000 rw-p 00000000 00:00 0
    35b1c00000-35b1dac000 r-xp 00000000 08:02 135870  /usr/lib64/libc-2.15.so
    35b1dac000-35b1fac000 ---p 001ac000 08:02 135870  /usr/lib64/libc-2.15.so
    35b1fac000-35b1fb0000 r--p 001ac000 08:02 135870  /usr/lib64/libc-2.15.so
    35b1fb0000-35b1fb2000 rw-p 001b0000 08:02 135870  /usr/lib64/libc-2.15.so
    ...
    f2c6ff8c000-7f2c7078c000 rw-p 00000000 00:00 0    [stack:986]
    ...
    7fffb2c0d000-7fffb2c2e000 rw-p 00000000 00:00 0   [stack]
    7fffb2d48000-7fffb2d49000 r-xp 00000000 00:00 0   [vdso]

              The  address  field is the address space in the process that the
              mapping occupies.  The perms field is a set of permissions:

                  r = read
                  w = write
                  x = execute
                  s = shared
                  p = private (copy on write)

              The offset field is the offset into the  file/whatever;  dev  is
              the  device (major:minor); inode is the inode on that device.  0
              indicates that no inode is associated with the memory region, as
              would be the case with BSS (uninitialized data).

              The  pathname field will usually be the file that is backing the
              mapping.  For ELF files, you can easily coordinate with the off-
              set  field  by  looking  at  the Offset field in the ELF program
              headers (readelf -l).

              There are additional helpful pseudo-paths:

                   [stack]
                          The  initial  process's  (also  known  as  the  main
                          thread's) stack.

                   [stack:<tid>] (since Linux 3.4)
                          A  thread's  stack (where the <tid> is a thread ID).
                          It corresponds to the /proc/[pid]/task/[tid]/ path.

                   [vdso] The virtual dynamically linked shared  object.   See
                          vdso(7).

                   [heap] The process's heap.

              If  the pathname field is blank, this is an anonymous mapping as
              obtained via mmap(2).  There is no easy way to  coordinate  this
              back  to a process's source, short of running it through gdb(1),
              strace(1), or similar.

              Under Linux 2.0, there is no field giving pathname.

       /proc/[pid]/mem
              This file can be used to access the pages of a process's  memory
              through open(2), read(2), and lseek(2).

              Permission  to  access  this file is governed by a ptrace access
              mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).

       /proc/[pid]/mountinfo (since Linux 2.6.26)
              This  file  contains  information  about  mount  points  in  the
              process's  mount  namespace  (see mount_namespaces(7)).  It sup-
              plies various information  (e.g.,  propagation  state,  root  of
              mount for bind mounts, identifier for each mount and its parent)
              that is missing from the (older)  /proc/[pid]/mounts  file,  and
              fixes  various  other problems with that file (e.g., nonextensi-
              bility, failure to distinguish per-mount  versus  per-superblock
              options).

              The file contains lines of the form:

36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
(1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)

              The  numbers  in  parentheses  are  labels  for the descriptions
              below:

              (1)  mount ID: a unique ID for the mount (may  be  reused  after
                   umount(2)).

              (2)  parent  ID:  the ID of the parent mount (or of self for the
                   top of the mount tree).

              (3)  major:minor: the value of st_dev for files on this filesys-
                   tem (see stat(2)).

              (4)  root: the pathname of the directory in the filesystem which
                   forms the root of this mount.

              (5)  mount point: the pathname of the mount  point  relative  to
                   the process's root directory.

              (6)  mount options: per-mount options.

              (7)  optional   fields:   zero   or  more  fields  of  the  form
                   "tag[:value]"; see below.

              (8)  separator: the end of the optional fields is  marked  by  a
                   single hyphen.

              (9)  filesystem   type:   the   filesystem   type  in  the  form
                   "type[.subtype]".

              (10) mount source: filesystem-specific information or "none".

              (11) super options: per-superblock options.

              Currently, the possible  optional  fields  are  shared,  master,
              propagate_from,  and  unbindable.  See mount_namespaces(7) for a
              description of these fields.  Parsers should ignore all unrecog-
              nized optional fields.

              For  more  information  on  mount  propagation  see:  Documenta-
              tion/filesystems/sharedsubtree.txt in the  Linux  kernel  source
              tree.

       /proc/[pid]/mounts (since Linux 2.4.19)
              This  file  lists  all  the filesystems currently mounted in the
              process's mount namespace (see mount_namespaces(7)).  The format
              of this file is documented in fstab(5).

              Since  kernel version 2.6.15, this file is pollable: after open-
              ing the file for  reading,  a  change  in  this  file  (i.e.,  a
              filesystem  mount  or unmount) causes select(2) to mark the file
              descriptor as having an exceptional condition, and  poll(2)  and
              epoll_wait(2)  mark  the  file as having a priority event (POLL-
              PRI).  (Before Linux 2.6.30, a change in this file was indicated
              by  the  file descriptor being marked as readable for select(2),
              and being marked as having an error condition  for  poll(2)  and
              epoll_wait(2).)

       /proc/[pid]/mountstats (since Linux 2.6.17)
              This  file exports information (statistics, configuration infor-
              mation) about the mount points in the process's mount  namespace
              (see mount_namespaces(7)).  Lines in this file have the form:

                  device /dev/sda7 mounted on /home with fstype ext3 [statistics]
                  (       1      )            ( 2 )             (3 ) (4)

              The fields in each line are:

              (1)  The  name  of the mounted device (or "nodevice" if there is
                   no corresponding device).

              (2)  The mount point within the filesystem tree.

              (3)  The filesystem type.

              (4)  Optional statistics and  configuration  information.   Cur-
                   rently  (as  at  Linux 2.6.26), only NFS filesystems export
                   information via this field.

              This file is readable only by the owner of the process.

       /proc/[pid]/net (since Linux 2.6.25)
              See the description of /proc/net.

       /proc/[pid]/ns/ (since Linux 3.0)
              This is a subdirectory containing one entry for  each  namespace
              that  supports being manipulated by setns(2).  For more informa-
              tion, see namespaces(7).

       /proc/[pid]/numa_maps (since Linux 2.6.14)
              See numa(7).

       /proc/[pid]/oom_adj (since Linux 2.6.11)
              This file can be used to adjust the score used to  select  which
              process  should  be  killed in an out-of-memory (OOM) situation.
              The kernel uses this value for  a  bit-shift  operation  of  the
              process's  oom_score value: valid values are in the range -16 to
              +15, plus the special  value  -17,  which  disables  OOM-killing
              altogether  for  this  process.   A positive score increases the
              likelihood of this process being killed  by  the  OOM-killer;  a
              negative score decreases the likelihood.

              The default value for this file is 0; a new process inherits its
              parent's  oom_adj  setting.   A  process  must   be   privileged
              (CAP_SYS_RESOURCE) to update this file.

              Since  Linux  2.6.36, use of this file is deprecated in favor of
              /proc/[pid]/oom_score_adj.

       /proc/[pid]/oom_score (since Linux 2.6.11)
              This file displays the current score that the  kernel  gives  to
              this process for the purpose of selecting a process for the OOM-
              killer.  A higher score means that the process is more likely to
              be  selected by the OOM-killer.  The basis for this score is the
              amount of memory used by the  process,  with  increases  (+)  or
              decreases (-) for factors including:

              * whether  the  process  creates a lot of children using fork(2)
                (+);

              * whether the process has been running a long time, or has  used
                a lot of CPU time (-);

              * whether the process has a low nice value (i.e., > 0) (+);

              * whether the process is privileged (-); and

              * whether the process is making direct hardware access (-).

              The  oom_score  also  reflects  the  adjustment specified by the
              oom_score_adj or oom_adj setting for the process.

       /proc/[pid]/oom_score_adj (since Linux 2.6.36)
              This file can be used to adjust the badness  heuristic  used  to
              select which process gets killed in out-of-memory conditions.

              The  badness  heuristic  assigns  a value to each candidate task
              ranging from 0 (never kill) to 1000 (always kill)  to  determine
              which  process  is targeted.  The units are roughly a proportion
              along that range of allowed  memory  the  process  may  allocate
              from, based on an estimation of its current memory and swap use.
              For example, if a task is using all allowed memory, its  badness
              score  will be 1000.  If it is using half of its allowed memory,
              its score will be 500.

              There is an additional factor included  in  the  badness  score:
              root processes are given 3% extra memory over other tasks.

              The  amount  of "allowed" memory depends on the context in which
              the OOM-killer was called.  If it is due to the memory  assigned
              to  the  allocating  task's  cpuset being exhausted, the allowed
              memory represents the set of mems assigned to that  cpuset  (see
              cpuset(7)).   If  it  is  due  to  a  mempolicy's  node(s) being
              exhausted, the allowed memory represents the  set  of  mempolicy
              nodes.   If  it  is  due to a memory limit (or swap limit) being
              reached, the allowed memory is that configured limit.   Finally,
              if  it  is  due  to  the  entire system being out of memory, the
              allowed memory represents all allocatable resources.

              The value of oom_score_adj is added to the badness score  before
              it  is  used to determine which task to kill.  Acceptable values
              range    from     -1000     (OOM_SCORE_ADJ_MIN)     to     +1000
              (OOM_SCORE_ADJ_MAX).   This  allows  user  space  to control the
              preference for OOM-killing, ranging  from  always  preferring  a
              certain  task  or completely disabling it from OOM killing.  The
              lowest possible value, -1000, is equivalent  to  disabling  OOM-
              killing  entirely  for  that task, since it will always report a
              badness score of 0.

              Consequently, it is very simple for user  space  to  define  the
              amount  of  memory  to  consider  for  each  task.   Setting  an
              oom_score_adj value of +500, for example, is roughly  equivalent
              to  allowing  the  remainder  of  tasks sharing the same system,
              cpuset, mempolicy, or memory  controller  resources  to  use  at
              least  50%  more  memory.   A  value of -500, on the other hand,
              would be roughly equivalent to discounting  50%  of  the  task's
              allowed  memory  from  being  considered  as scoring against the
              task.

              For    backward    compatibility    with    previous    kernels,
              /proc/[pid]/oom_adj can still be used to tune the badness score.
              Its value is scaled linearly with oom_score_adj.

              Writing to /proc/[pid]/oom_score_adj or /proc/[pid]/oom_adj will
              change the other with its scaled value.

       /proc/[pid]/pagemap (since Linux 2.6.25)
              This  file  shows  the  mapping of each of the process's virtual
              pages into physical page frames or swap area.  It  contains  one
              64-bit  value  for  each virtual page, with the bits set as fol-
              lows:

                   63     If set, the page is present in RAM.

                   62     If set, the page is in swap space

                   61 (since Linux 3.5)
                          The page is a file-mapped page or a shared anonymous
                          page.

                   60-56 (since Linux 3.11)
                          Zero

                   55 (since Linux 3.11)
                          PTE  is soft-dirty (see the kernel source file Docu-
                          mentation/vm/soft-dirty.txt).

                   54-0   If the page is present in RAM (bit 63),  then  these
                          bits  provide  the  page  frame number, which can be
                          used to index /proc/kpageflags and /proc/kpagecount.
                          If  the  page is present in swap (bit 62), then bits
                          4-0 give the swap type, and  bits  54-5  encode  the
                          swap offset.

              Before Linux 3.11, bits 60-55 were used to encode the base-2 log
              of the page size.

              To employ /proc/[pid]/pagemap efficiently, use  /proc/[pid]/maps
              to  determine which areas of memory are actually mapped and seek
              to skip over unmapped regions.

              The  /proc/[pid]/pagemap  file  is  present  only  if  the  CON-
              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

              Permission  to  access  this file is governed by a ptrace access
              mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/personality (since Linux 2.6.28)
              This read-only file exposes the process's execution  domain,  as
              set  by  personality(2).   The value is displayed in hexadecimal
              notation.

              Permission to access this file is governed by  a  ptrace  access
              mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).

       /proc/[pid]/root
              UNIX  and  Linux  support  the idea of a per-process root of the
              filesystem, set by the chroot(2) system call.  This  file  is  a
              symbolic  link  that points to the process's root directory, and
              behaves in the same way as exe, and fd/*.

              Note however that this file is not merely a symbolic  link.   It
              provides  the  same view of the filesystem (including namespaces
              and the set of per-process mounts) as the  process  itself.   An
              example  illustrates  this  point.   In one terminal, we start a
              shell in new user and mount namespaces, and  in  that  shell  we
              create some new mount points:

                  $ PS1='sh1# ' unshare -Urnm
                  sh1# mount -t tmpfs tmpfs /etc  # Mount empty tmpfs at /etc
                  sh1# mount --bind /usr /dev     # Mount /usr at /dev
                  sh1# echo $$
                  27123

              In  a second terminal window, in the initial mount namespace, we
              look at the contents of the corresponding mounts in the  initial
              and new namespaces:

                  $ PS1='sh2# ' sudo sh
                  sh2# ls /etc | wc -l                  # In initial NS
                  309
                  sh2# ls /proc/27123/root/etc | wc -l  # /etc in other NS
                  0                                     # The empty tmpfs dir
                  sh2# ls /dev | wc -l                  # In initial NS
                  205
                  sh2# ls /proc/27123/root/dev | wc -l  # /dev in other NS
                  11                                    # Actually bind
                                                        # mounted to /usr
                  sh2# ls /usr | wc -l                  # /usr in initial NS
                  11

              In a multithreaded process, the contents of the /proc/[pid]/root
              symbolic link are not available if the main thread  has  already
              terminated (typically by calling pthread_exit(3)).

              Permission  to  dereference  or read (readlink(2)) this symbolic
              link    is    governed    by    a     ptrace     access     mode
              PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/seccomp (Linux 2.6.12 to 2.6.22)
              This  file  can  be used to read and change the process's secure
              computing (seccomp) mode setting.  It contains the  value  0  if
              the  process  is not in seccomp mode, and 1 if the process is in
              strict seccomp mode (see seccomp(2)).  Writing 1  to  this  file
              places  the  process irreversibly in strict seccomp mode.  (Fur-
              ther attempts to write to the file fail with the EPERM error.)

              In Linux 2.6.23, this file went away,  to  be  replaced  by  the
              prctl(2) PR_GET_SECCOMP and PR_SET_SECCOMP operations (and later
              by seccomp(2) and the Seccomp field in /proc/[pid]/status).

       /proc/[pid]/setgroups (since Linux 3.19)
              See user_namespaces(7).

       /proc/[pid]/smaps (since Linux 2.6.14)
              This file shows memory consumption for  each  of  the  process's
              mappings.  (The pmap(1) command displays similar information, in
              a form that may be easier for parsing.)  For each mapping  there
              is a series of lines such as the following:

                  00400000-0048a000 r-xp 00000000 fd:03 960637       /bin/bash
                  Size:                552 kB
                  Rss:                 460 kB
                  Pss:                 100 kB
                  Shared_Clean:        452 kB
                  Shared_Dirty:          0 kB
                  Private_Clean:         8 kB
                  Private_Dirty:         0 kB
                  Referenced:          460 kB
                  Anonymous:             0 kB
                  AnonHugePages:         0 kB
                  ShmemHugePages:        0 kB
                  ShmemPmdMapped:        0 kB
                  Swap:                  0 kB
                  KernelPageSize:        4 kB
                  MMUPageSize:           4 kB
                  KernelPageSize:        4 kB
                  MMUPageSize:           4 kB
                  Locked:                0 kB
                  ProtectionKey:         0
                  VmFlags: rd ex mr mw me dw

              The  first  of these lines shows the same information as is dis-
              played for the mapping in /proc/[pid]/maps.  The following lines
              show  the size of the mapping, the amount of the mapping that is
              currently resident in RAM ("Rss"),  the  process's  proportional
              share  of  this  mapping  ("Pss"), the number of clean and dirty
              shared pages in the mapping, and the number of clean  and  dirty
              private pages in the mapping.  "Referenced" indicates the amount
              of memory currently marked as referenced or  accessed.   "Anony-
              mous"  shows  the  amount  of memory that does not belong to any
              file.  "Swap" shows how much would-be-anonymous memory  is  also
              used, but out on swap.

              The  "KernelPageSize" line (available since Linux 2.6.29) is the
              page size used by the kernel to back the  virtual  memory  area.
              This  matches the size used by the MMU in the majority of cases.
              However, one counter-example occurs on PPC64 kernels  whereby  a
              kernel  using  64kB  as a base page size may still use 4kB pages
              for the  MMU  on  older  processors.   To  distinguish  the  two
              attributes,  the  "MMUPageSize" line (also available since Linux
              2.6.29) reports the page size used by the MMU.

              The "Locked" indicates whether the mapping is locked  in  memory
              or not.

              The  "ProtectionKey"  line  (available  since  Linux 4.9, on x86
              only) contains the memory protection key (see pkeys(7))  associ-
              ated  with  the virtual memory area.  This entry is present only
              if the kernel was built with the CONFIG_X86_INTEL_MEMORY_PROTEC-
              TION_KEYS configuration option.

              The  "VmFlags"  line  (available since Linux 3.8) represents the
              kernel flags associated with the virtual  memory  area,  encoded
              using the following two-letter codes:

                  rd  - readable
                  wr  - writable
                  ex  - executable
                  sh  - shared
                  mr  - may read
                  mw  - may write
                  me  - may execute
                  ms  - may share
                  gd  - stack segment grows down
                  pf  - pure PFN range
                  dw  - disabled write to the mapped file
                  lo  - pages are locked in memory
                  io  - memory mapped I/O area
                  sr  - sequential read advise provided
                  rr  - random read advise provided
                  dc  - do not copy area on fork
                  de  - do not expand area on remapping
                  ac  - area is accountable
                  nr  - swap space is not reserved for the area
                  ht  - area uses huge tlb pages
                  nl  - non-linear mapping
                  ar  - architecture specific flag
                  dd  - do not include area into core dump
                  sd  - soft-dirty flag
                  mm  - mixed map area
                  hg  - huge page advise flag
                  nh  - no-huge page advise flag
                  mg  - mergeable advise flag

              "ProtectionKey"  field  contains  the memory protection key (see
              pkeys(5)) associated with the virtual memory area.  Present only
              if the kernel was built with the CONFIG_X86_INTEL_MEMORY_PROTEC-
              TION_KEYS configuration option. (since Linux 4.6)

              The  /proc/[pid]/smaps  file  is  present  only  if   the   CON-
              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/[pid]/stack (since Linux 2.6.29)
              This  file  provides  a  symbolic trace of the function calls in
              this process's kernel stack.  This file is provided only if  the
              kernel   was  built  with  the  CONFIG_STACKTRACE  configuration
              option.

              Permission to access this file is governed by  a  ptrace  access
              mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).

       /proc/[pid]/stat
              Status  information  about  the process.  This is used by ps(1).
              It is defined in the kernel source file fs/proc/array.c.

              The fields, in order, with their proper scanf(3)  format  speci-
              fiers, are listed below.  Whether or not certain of these fields
              display valid information is governed by a  ptrace  access  mode
              PTRACE_MODE_READ_FSCREDS | PTRACE_MODE_NOAUDIT  check  (refer to
              ptrace(2)).  If the check denies access, then the field value is
              displayed  as  0.   The  affected  fields are indicated with the
              marking [PT].

              (1) pid  %d
                        The process ID.

              (2) comm  %s
                        The filename of the executable, in parentheses.   This
                        is  visible  whether  or not the executable is swapped
                        out.

              (3) state  %c
                        One of the following  characters,  indicating  process
                        state:

                        R  Running

                        S  Sleeping in an interruptible wait

                        D  Waiting in uninterruptible disk sleep

                        Z  Zombie

                        T  Stopped  (on  a  signal)  or  (before Linux 2.6.33)
                           trace stopped

                        t  Tracing stop (Linux 2.6.33 onward)

                        W  Paging (only before Linux 2.6.0)

                        X  Dead (from Linux 2.6.0 onward)

                        x  Dead (Linux 2.6.33 to 3.13 only)

                        K  Wakekill (Linux 2.6.33 to 3.13 only)

                        W  Waking (Linux 2.6.33 to 3.13 only)

                        P  Parked (Linux 3.9 to 3.13 only)

              (4) ppid  %d
                        The PID of the parent of this process.

              (5) pgrp  %d
                        The process group ID of the process.

              (6) session  %d
                        The session ID of the process.

              (7) tty_nr  %d
                        The controlling terminal of the process.   (The  minor
                        device  number is contained in the combination of bits
                        31 to 20 and 7 to 0; the major  device  number  is  in
                        bits 15 to 8.)

              (8) tpgid  %d
                        The ID of the foreground process group of the control-
                        ling terminal of the process.

              (9) flags  %u
                        The kernel flags word of the process.  For  bit  mean-
                        ings,  see the PF_* defines in the Linux kernel source
                        file include/linux/sched.h.   Details  depend  on  the
                        kernel version.

                        The format for this field was %lu before Linux 2.6.

              (10) minflt  %lu
                        The  number of minor faults the process has made which
                        have not required loading a memory page from disk.

              (11) cminflt  %lu
                        The number of minor faults that the process's  waited-
                        for children have made.

              (12) majflt  %lu
                        The  number of major faults the process has made which
                        have required loading a memory page from disk.

              (13) cmajflt  %lu
                        The number of major faults that the process's  waited-
                        for children have made.

              (14) utime  %lu
                        Amount of time that this process has been scheduled in
                        user  mode,  measured  in  clock  ticks   (divide   by
                        sysconf(_SC_CLK_TCK)).    This  includes  guest  time,
                        guest_time (time spent  running  a  virtual  CPU,  see
                        below), so that applications that are not aware of the
                        guest time field do not lose that time from their cal-
                        culations.

              (15) stime  %lu
                        Amount of time that this process has been scheduled in
                        kernel  mode,  measured  in  clock  ticks  (divide  by
                        sysconf(_SC_CLK_TCK)).

              (16) cutime  %ld
                        Amount of time that this process's waited-for children
                        have been scheduled in user mode,  measured  in  clock
                        ticks  (divide  by  sysconf(_SC_CLK_TCK)).   (See also
                        times(2).)   This  includes  guest  time,  cguest_time
                        (time spent running a virtual CPU, see below).

              (17) cstime  %ld
                        Amount of time that this process's waited-for children
                        have been scheduled in kernel mode, measured in  clock
                        ticks (divide by sysconf(_SC_CLK_TCK)).

              (18) priority  %ld
                        (Explanation  for  Linux  2.6) For processes running a
                        real-time  scheduling  policy   (policy   below;   see
                        sched_setscheduler(2)), this is the negated scheduling
                        priority, minus one; that is, a number in the range -2
                        to  -100,  corresponding  to real-time priorities 1 to
                        99.   For  processes  running  under  a  non-real-time
                        scheduling policy, this is the raw nice value (setpri-
                        ority(2)) as represented in the  kernel.   The  kernel
                        stores nice values as numbers in the range 0 (high) to
                        39 (low), corresponding to the user-visible nice range
                        of -20 to 19.

                        Before Linux 2.6, this was a scaled value based on the
                        scheduler weighting given to this process.

              (19) nice  %ld
                        The nice value (see setpriority(2)), a  value  in  the
                        range 19 (low priority) to -20 (high priority).

              (20) num_threads  %ld
                        Number  of  threads in this process (since Linux 2.6).
                        Before kernel 2.6, this field was hard coded to 0 as a
                        placeholder for an earlier removed field.

              (21) itrealvalue  %ld
                        The time in jiffies before the next SIGALRM is sent to
                        the process due to an interval  timer.   Since  kernel
                        2.6.17,  this  field  is  no longer maintained, and is
                        hard coded as 0.

              (22) starttime  %llu
                        The time the process started after  system  boot.   In
                        kernels  before Linux 2.6, this value was expressed in
                        jiffies.  Since Linux 2.6, the value is  expressed  in
                        clock ticks (divide by sysconf(_SC_CLK_TCK)).

                        The format for this field was %lu before Linux 2.6.

              (23) vsize  %lu
                        Virtual memory size in bytes.

              (24) rss  %ld
                        Resident  Set Size: number of pages the process has in
                        real memory.  This  is  just  the  pages  which  count
                        toward  text,  data,  or  stack  space.  This does not
                        include pages which have not been demand-loaded in, or
                        which are swapped out.

              (25) rsslim  %lu
                        Current soft limit in bytes on the rss of the process;
                        see the description of RLIMIT_RSS in getrlimit(2).

              (26) startcode  %lu  [PT]
                        The address above which program text can run.

              (27) endcode  %lu  [PT]
                        The address below which program text can run.

              (28) startstack  %lu  [PT]
                        The address of the start (i.e., bottom) of the stack.

              (29) kstkesp  %lu  [PT]
                        The current value of ESP (stack pointer), as found  in
                        the kernel stack page for the process.

              (30) kstkeip  %lu  [PT]
                        The current EIP (instruction pointer).

              (31) signal  %lu
                        The  bitmap of pending signals, displayed as a decimal
                        number.  Obsolete, because it does not provide  infor-
                        mation  on  real-time  signals; use /proc/[pid]/status
                        instead.

              (32) blocked  %lu
                        The bitmap of blocked signals, displayed as a  decimal
                        number.   Obsolete, because it does not provide infor-
                        mation on real-time  signals;  use  /proc/[pid]/status
                        instead.

              (33) sigignore  %lu
                        The  bitmap of ignored signals, displayed as a decimal
                        number.  Obsolete, because it does not provide  infor-
                        mation  on  real-time  signals; use /proc/[pid]/status
                        instead.

              (34) sigcatch  %lu
                        The bitmap of caught signals, displayed as  a  decimal
                        number.   Obsolete, because it does not provide infor-
                        mation on real-time  signals;  use  /proc/[pid]/status
                        instead.

              (35) wchan  %lu  [PT]
                        This is the "channel" in which the process is waiting.
                        It is the address of a location in  the  kernel  where
                        the  process  is sleeping.  The corresponding symbolic
                        name can be found in /proc/[pid]/wchan.

              (36) nswap  %lu
                        Number of pages swapped (not maintained).

              (37) cnswap  %lu
                        Cumulative nswap for child processes (not maintained).

              (38) exit_signal  %d  (since Linux 2.1.22)
                        Signal to be sent to parent when we die.

              (39) processor  %d  (since Linux 2.2.8)
                        CPU number last executed on.

              (40) rt_priority  %u  (since Linux 2.5.19)
                        Real-time scheduling priority, a number in the range 1
                        to  99  for processes scheduled under a real-time pol-
                        icy,  or   0,   for   non-real-time   processes   (see
                        sched_setscheduler(2)).

              (41) policy  %u  (since Linux 2.5.19)
                        Scheduling policy (see sched_setscheduler(2)).  Decode
                        using the SCHED_* constants in linux/sched.h.

                        The format for this field was %lu before Linux 2.6.22.

              (42) delayacct_blkio_ticks  %llu  (since Linux 2.6.18)
                        Aggregated block I/O delays, measured in  clock  ticks
                        (centiseconds).

              (43) guest_time  %lu  (since Linux 2.6.24)
                        Guest  time  of the process (time spent running a vir-
                        tual CPU for a guest operating  system),  measured  in
                        clock ticks (divide by sysconf(_SC_CLK_TCK)).

              (44) cguest_time  %ld  (since Linux 2.6.24)
                        Guest  time  of  the  process's  children, measured in
                        clock ticks (divide by sysconf(_SC_CLK_TCK)).

              (45) start_data  %lu  (since Linux 3.3)  [PT]
                        Address above which program initialized and uninitial-
                        ized (BSS) data are placed.

              (46) end_data  %lu  (since Linux 3.3)  [PT]
                        Address below which program initialized and uninitial-
                        ized (BSS) data are placed.

              (47) start_brk  %lu  (since Linux 3.3)  [PT]
                        Address above which program heap can be expanded  with
                        brk(2).

              (48) arg_start  %lu  (since Linux 3.5)  [PT]
                        Address  above  which  program  command-line arguments
                        (argv) are placed.

              (49) arg_end  %lu  (since Linux 3.5)  [PT]
                        Address below program  command-line  arguments  (argv)
                        are placed.

              (50) env_start  %lu  (since Linux 3.5)  [PT]
                        Address above which program environment is placed.

              (51) env_end  %lu  (since Linux 3.5)  [PT]
                        Address below which program environment is placed.

              (52) exit_code  %d  (since Linux 3.5)  [PT]
                        The thread's exit status in the form reported by wait-
                        pid(2).

       /proc/[pid]/statm
              Provides information about memory usage, measured in pages.  The
              columns are:

                  size       (1) total program size
                             (same as VmSize in /proc/[pid]/status)
                  resident   (2) resident set size
                             (same as VmRSS in /proc/[pid]/status)
                  shared     (3) number of resident shared pages (i.e., backed by a file)
                             (same as RssFile+RssShmem in /proc/[pid]/status)
                  text       (4) text (code)
                  lib        (5) library (unused since Linux 2.6; always 0)
                  data       (6) data + stack
                  dt         (7) dirty pages (unused since Linux 2.6; always 0)

       /proc/[pid]/status
              Provides   much  of  the  information  in  /proc/[pid]/stat  and
              /proc/[pid]/statm in a format that's easier for humans to parse.
              Here's an example:

                  $ cat /proc/$$/status
                  Name:   bash
                  Umask:  0022
                  State:  S (sleeping)
                  Tgid:   17248
                  Ngid:   0
                  Pid:    17248
                  PPid:   17200
                  TracerPid:      0
                  Uid:    1000    1000    1000    1000
                  Gid:    100     100     100     100
                  FDSize: 256
                  Groups: 16 33 100
                  NStgid: 17248
                  NSpid:  17248
                  NSpgid: 17248
                  NSsid:  17200
                  VmPeak:     131168 kB
                  VmSize:     131168 kB
                  VmLck:           0 kB
                  VmPin:           0 kB
                  VmHWM:       13484 kB
                  VmRSS:       13484 kB
                  RssAnon:     10264 kB
                  RssFile:      3220 kB
                  RssShmem:        0 kB
                  VmData:      10332 kB
                  VmStk:         136 kB
                  VmExe:         992 kB
                  VmLib:        2104 kB
                  VmPTE:          76 kB
                  VmPMD:          12 kB
                  VmSwap:          0 kB
                  HugetlbPages:          0 kB        # 4.4
                  Threads:        1
                  SigQ:   0/3067
                  SigPnd: 0000000000000000
                  ShdPnd: 0000000000000000
                  SigBlk: 0000000000010000
                  SigIgn: 0000000000384004
                  SigCgt: 000000004b813efb
                  CapInh: 0000000000000000
                  CapPrm: 0000000000000000
                  CapEff: 0000000000000000
                  CapBnd: ffffffffffffffff
                  CapAmb:   0000000000000000
                  NoNewPrivs:     0
                  Seccomp:        0
                  Cpus_allowed:   00000001
                  Cpus_allowed_list:      0
                  Mems_allowed:   1
                  Mems_allowed_list:      0
                  voluntary_ctxt_switches:        150
                  nonvoluntary_ctxt_switches:     545

              The fields are as follows:

              * Name: Command run by this process.

              * Umask:  Process umask, expressed in octal with a leading zero;
                see umask(2).  (Since Linux 4.7.)

              * State: Current state of the process.  One of "R (running)", "S
                (sleeping)",  "D  (disk  sleep)",  "T  (stopped)", "T (tracing
                stop)", "Z (zombie)", or "X (dead)".

              * Tgid: Thread group ID (i.e., Process ID).

              * Ngid: NUMA group ID (0 if none; since Linux 3.13).

              * Pid: Thread ID (see gettid(2)).

              * PPid: PID of parent process.

              * TracerPid: PID of process tracing this process (0 if not being
                traced).

              * Uid,  Gid:  Real,  effective,  saved  set, and filesystem UIDs
                (GIDs).

              * FDSize: Number of file descriptor slots currently allocated.

              * Groups: Supplementary group list.

              * NStgid : Thread group ID (i.e., PID) in each of the PID names-
                paces  of  which  [pid] is a member.  The leftmost entry shows
                the value with respect to the PID  namespace  of  the  reading
                process,  followed  by  the value in successively nested inner
                namespaces.  (Since Linux 4.1.)

              * NSpid: Thread ID in each of the PID namespaces of which  [pid]
                is  a  member.   The fields are ordered as for NStgid.  (Since
                Linux 4.1.)

              * NSpgid: Process group ID in each  of  the  PID  namespaces  of
                which  [pid]  is a member.  The fields are ordered as for NSt-
                gid.  (Since Linux 4.1.)

              * NSsid: descendant namespace session ID hierarchy Session ID in
                each  of  the  PID namespaces of which [pid] is a member.  The
                fields are ordered as for NStgid.  (Since Linux 4.1.)

              * VmPeak: Peak virtual memory size.

              * VmSize: Virtual memory size.

              * VmLck: Locked memory size (see mlock(3)).

              * VmPin: Pinned memory size (since Linux 3.2).  These are  pages
                that can't be moved because something needs to directly access
                physical memory.

              * VmHWM: Peak resident set size ("high water mark").

              * VmRSS: Resident set size.  Note that the value here is the sum
                of RssAnon, RssFile, and RssShmem.

              * RssAnon:  Size  of  resident  anonymous  memory.  (since Linux
                4.5).

              * RssFile: Size of resident file mappings.  (since Linux 4.5).

              * RssShmem: Size of resident shared memory  (includes  System  V
                shared  memory,  mappings  from tmpfs(5), and shared anonymous
                mappings).  (since Linux 4.5).

              * VmData, VmStk, VmExe: Size of data, stack, and text segments.

              * VmLib: Shared library code size.

              * VmPTE: Page table entries size (since Linux 2.6.10).

              * VmPMD: Size of second-level page tables (since Linux 4.0).

              * VmSwap: Swapped-out virtual memory size by  anonymous  private
                pages; shmem swap usage is not included (since Linux 2.6.34).

              * HugetlbPages:  Size  of hugetlb memory portions.  (since Linux
                4.4).

              * Threads: Number of threads in process containing this thread.

              * SigQ: This field contains  two  slash-separated  numbers  that
                relate to queued signals for the real user ID of this process.
                The first of these is the number of currently  queued  signals
                for this real user ID, and the second is the resource limit on
                the number  of  queued  signals  for  this  process  (see  the
                description of RLIMIT_SIGPENDING in getrlimit(2)).

              * SigPnd,  ShdPnd:  Number of signals pending for thread and for
                process as a whole (see pthreads(7) and signal(7)).

              * SigBlk,  SigIgn,  SigCgt:  Masks  indicating   signals   being
                blocked, ignored, and caught (see signal(7)).

              * CapInh,  CapPrm,  CapEff:  Masks  of  capabilities  enabled in
                inheritable, permitted,  and  effective  sets  (see  capabili-
                ties(7)).

              * CapBnd: Capability Bounding set (since Linux 2.6.26, see capa-
                bilities(7)).

              * CapAmb: Ambient capability set (since Linux 4.3, see capabili-
                ties(7)).

              * NoNewPrivs:  Value  of the no_new_privs bit (since Linux 4.10,
                see prctl(2)).

              * Seccomp: Seccomp mode of the process  (since  Linux  3.8,  see
                seccomp(2)).   0  means  SECCOMP_MODE_DISABLED;  1  means SEC-
                COMP_MODE_STRICT; 2 means SECCOMP_MODE_FILTER.  This field  is
                provided  only if the kernel was built with the CONFIG_SECCOMP
                kernel configuration option enabled.

              * Cpus_allowed: Mask of CPUs  on  which  this  process  may  run
                (since Linux 2.6.24, see cpuset(7)).

              * Cpus_allowed_list:  Same  as  previous,  but  in "list format"
                (since Linux 2.6.26, see cpuset(7)).

              * Mems_allowed: Mask of memory nodes  allowed  to  this  process
                (since Linux 2.6.24, see cpuset(7)).

              * Mems_allowed_list:  Same  as  previous,  but  in "list format"
                (since Linux 2.6.26, see cpuset(7)).

              * voluntary_ctxt_switches, nonvoluntary_ctxt_switches: Number of
                voluntary   and  involuntary  context  switches  (since  Linux
                2.6.23).

       /proc/[pid]/syscall (since Linux 2.6.27)
              This file exposes the system call number and argument  registers
              for  the  system  call  currently being executed by the process,
              followed by the values of the stack pointer and program  counter
              registers.   The  values  of  all  six  argument  registers  are
              exposed, although most system calls use fewer registers.

              If the process is blocked, but not in a system  call,  then  the
              file displays -1 in place of the system call number, followed by
              just the values of the stack pointer and  program  counter.   If
              process  is  not blocked, then the file contains just the string
              "running".

              This file is present only if the kernel was configured with CON-
              FIG_HAVE_ARCH_TRACEHOOK.

              Permission  to  access  this file is governed by a ptrace access
              mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).

       /proc/[pid]/task (since Linux 2.6.0-test6)
              This is a directory that  contains  one  subdirectory  for  each
              thread  in  the  process.   The name of each subdirectory is the
              numerical thread ID  ([tid])  of  the  thread  (see  gettid(2)).
              Within  each  of  these  subdirectories, there is a set of files
              with the same names and contents as under the /proc/[pid] direc-
              tories.  For attributes that are shared by all threads, the con-
              tents for each of the files under the task/[tid]  subdirectories
              will  be  the  same  as  in the corresponding file in the parent
              /proc/[pid] directory (e.g., in a multithreaded process, all  of
              the  task/[tid]/cwd  files  will  have  the  same  value  as the
              /proc/[pid]/cwd file in the parent directory, since all  of  the
              threads in a process share a working directory).  For attributes
              that are distinct for each thread, the corresponding files under
              task/[tid]  may  have  different values (e.g., various fields in
              each of the task/[tid]/status files may be  different  for  each
              thread),  or  they  might not exist in /proc/[pid] at all.  In a
              multithreaded process,  the  contents  of  the  /proc/[pid]/task
              directory  are not available if the main thread has already ter-
              minated (typically by calling pthread_exit(3)).

       /proc/[pid]/task/[tid]/children (since Linux 3.5)
              A space-separated list of child tasks of this task.  Each  child
              task is represented by its TID.

              This option is intended for use by the checkpoint-restore (CRIU)
              system, and reliably provides a list of children only if all  of
              the  child  processes  are  stopped or frozen.  It does not work
              properly if children of the target task exit while the  file  is
              being  read!  Exiting children may cause non-exiting children to
              be omitted from the list.  This makes this interface  even  more
              unreliable  than  classic  PID-based approaches if the inspected
              task and its children aren't frozen, and most code should proba-
              bly not use this interface.

              Until  Linux  4.2, the presence of this file was governed by the
              CONFIG_CHECKPOINT_RESTORE kernel  configuration  option.   Since
              Linux 4.2, it is governed by the CONFIG_PROC_CHILDREN option.

       /proc/[pid]/timers (since Linux 3.10)
              A  list  of  the  POSIX  timers for this process.  Each timer is
              listed with a line that starts with the string "ID:".  For exam-
              ple:

                  ID: 1
                  signal: 60/00007fff86e452a8
                  notify: signal/pid.2634
                  ClockID: 0
                  ID: 0
                  signal: 60/00007fff86e452a8
                  notify: signal/pid.2634
                  ClockID: 1

              The lines shown for each timer have the following meanings:

              ID     The ID for this timer.  This is not the same as the timer
                     ID returned by timer_create(2); rather, it  is  the  same
                     kernel-internal  ID  that is available via the si_timerid
                     field of the siginfo_t structure (see sigaction(2)).

              signal This is the signal number that this timer uses to deliver
                     notifications   followed   by   a  slash,  and  then  the
                     sigev_value value supplied to the signal handler.   Valid
                     only for timers that notify via a signal.

              notify The  part  before  the slash specifies the mechanism that
                     this timer uses to deliver notifications, and is  one  of
                     "thread", "signal", or "none".  Immediately following the
                     slash  is  either  the  string  "tid"  for  timers   with
                     SIGEV_THREAD_ID  notification,  or  "pid" for timers that
                     notify by other mechanisms.  Following the "." is the PID
                     of  the  process  (or the kernel thread ID of the thread)
                     that will be delivered a signal  if  the  timer  delivers
                     notifications via a signal.

              ClockID
                     This  field  identifies the clock that the timer uses for
                     measuring time.  For most clocks, this is a  number  that
                     matches  one  of the user-space CLOCK_* constants exposed
                     via <time.h>.   CLOCK_PROCESS_CPUTIME_ID  timers  display
                     with     a     value     of    -6    in    this    field.
                     CLOCK_THREAD_CPUTIME_ID timers display with a value of -2
                     in this field.

              This  file is available only when the kernel was configured with
              CONFIG_CHECKPOINT_RESTORE.

       /proc/[pid]/timerslack_ns (since Linux 4.6)
              This file exposes the process's  "current"  timer  slack  value,
              expressed  in  nanoseconds.   The file is writable, allowing the
              process's timer slack value to be changed.  Writing  0  to  this
              file  resets  the  "current"  timer slack to the "default" timer
              slack  value.   For  further  details,  see  the  discussion  of
              PR_SET_TIMERSLACK in prctl(2).

              Initially,  permission  to  access  this  file was governed by a
              ptrace  access  mode   PTRACE_MODE_ATTACH_FSCREDS   check   (see
              ptrace(2)).   However, this was subsequently deemed too strict a
              requirement (and had the side effect that requiring a process to
              have  the  CAP_SYS_PTRACE capability would also allow it to view
              and change any process's memory).  Therefore, since  Linux  4.9,
              only  the (weaker) CAP_SYS_NICE capability is required to access
              this file.

       /proc/[pid]/uid_map, /proc/[pid]/gid_map (since Linux 3.5)
              See user_namespaces(7).

       /proc/[pid]/wchan (since Linux 2.6.0)
              The symbolic name corresponding to the location  in  the  kernel
              where the process is sleeping.

              Permission  to  access  this file is governed by a ptrace access
              mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/apm
              Advanced power management version and battery  information  when
              CONFIG_APM is defined at kernel compilation time.

       /proc/buddyinfo
              This file contains information which is used for diagnosing mem-
              ory fragmentation issues.  Each line starts with the identifica-
              tion  of  the node and the name of the zone which together iden-
              tify a memory region This is  then  followed  by  the  count  of
              available  chunks  of  a  certain order in which these zones are
              split.  The size in bytes of a certain order  is  given  by  the
              formula:

                  (2^order) * PAGE_SIZE

              The  binary  buddy  allocator  algorithm  inside the kernel will
              split one chunk into two chunks of a smaller  order  (thus  with
              half  the size) or combine two contiguous chunks into one larger
              chunk of a higher order (thus with double the size)  to  satisfy
              allocation  requests  and  to counter memory fragmentation.  The
              order matches the column number, when starting to count at zero.

              For example on a x86_64 system:

  Node 0, zone     DMA     1    1    1    0    2    1    1    0    1    1    3
  Node 0, zone   DMA32    65   47    4   81   52   28   13   10    5    1  404
  Node 0, zone  Normal   216   55  189  101   84   38   37   27    5    3  587

              In this example, there is one node containing  three  zones  and
              there are 11 different chunk sizes.  If the page size is 4 kilo-
              bytes, then the first zone called  DMA  (on  x86  the  first  16
              megabyte  of memory) has 1 chunk of 4 kilobytes (order 0) avail-
              able and has 3 chunks of 4 megabytes (order 10) available.

              If the memory is heavily fragmented,  the  counters  for  higher
              order  chunks  will  be  zero and allocation of large contiguous
              areas will fail.

              Further information about the zones can be found in  /proc/zone-
              info.

       /proc/bus
              Contains subdirectories for installed busses.

       /proc/bus/pccard
              Subdirectory  for  PCMCIA  devices  when CONFIG_PCMCIA is set at
              kernel compilation time.

       /proc/bus/pccard/drivers

       /proc/bus/pci
              Contains various bus subdirectories and pseudo-files  containing
              information  about  PCI  busses,  installed  devices, and device
              drivers.  Some of these files are not ASCII.

       /proc/bus/pci/devices
              Information about PCI devices.  They  may  be  accessed  through
              lspci(8) and setpci(8).

       /proc/cgroups (since Linux 2.6.24)
              See cgroups(7).

       /proc/cmdline
              Arguments  passed  to the Linux kernel at boot time.  Often done
              via a boot manager such as lilo(8) or grub(8).

       /proc/config.gz (since Linux 2.6)
              This file exposes the configuration options that  were  used  to
              build  the  currently running kernel, in the same format as they
              would be shown in the .config file that resulted when  configur-
              ing  the  kernel  (using make xconfig, make config, or similar).
              The file contents are compressed;  view  or  search  them  using
              zcat(1)  and  zgrep(1).  As long as no changes have been made to
              the following file, the contents of /proc/config.gz are the same
              as those provided by:

                  cat /lib/modules/$(uname -r)/build/.config

              /proc/config.gz  is  provided  only  if the kernel is configured
              with CONFIG_IKCONFIG_PROC.

       /proc/crypto
              A list of the ciphers provided by the kernel  crypto  API.   For
              details,  see  the  kernel Linux Kernel Crypto API documentation
              available  under  the   kernel   source   directory   Documenta-
              tion/crypto/ (or Documentation/DocBook before 4.10; the documen-
              tation can be built using a command such as make htmldocs in the
              root directory of the kernel source tree).

       /proc/cpuinfo
              This  is  a  collection of CPU and system architecture dependent
              items, for each supported architecture a  different  list.   Two
              common   entries  are  processor  which  gives  CPU  number  and
              bogomips; a system constant that  is  calculated  during  kernel
              initialization.   SMP  machines  have  information for each CPU.
              The lscpu(1) command gathers its information from this file.

       /proc/devices
              Text listing of major numbers and device groups.   This  can  be
              used by MAKEDEV scripts for consistency with the kernel.

       /proc/diskstats (since Linux 2.5.69)
              This  file  contains  disk  I/O statistics for each disk device.
              See the Linux kernel source file  Documentation/iostats.txt  for
              further information.

       /proc/dma
              This  is a list of the registered ISA DMA (direct memory access)
              channels in use.

       /proc/driver
              Empty subdirectory.

       /proc/execdomains
              List of the execution domains (ABI personalities).

       /proc/fb
              Frame buffer information when CONFIG_FB is defined during kernel
              compilation.

       /proc/filesystems
              A  text  listing  of  the filesystems which are supported by the
              kernel, namely filesystems which were compiled into  the  kernel
              or  whose  kernel  modules  are  currently  loaded.   (See  also
              filesystems(5).)  If a filesystem is marked with  "nodev",  this
              means  that  it  does  not  require a block device to be mounted
              (e.g., virtual filesystem, network filesystem).

              Incidentally, this file may be used by mount(8) when no filesys-
              tem  is specified and it didn't manage to determine the filesys-
              tem type.  Then filesystems contained in  this  file  are  tried
              (excepted those that are marked with "nodev").

       /proc/fs
              Contains subdirectories that in turn contain files with informa-
              tion about (certain) mounted filesystems.

       /proc/ide
              This directory exists on systems with the IDE  bus.   There  are
              directories  for  each  IDE  channel and attached device.  Files
              include:

                  cache              buffer size in KB
                  capacity           number of sectors
                  driver             driver version
                  geometry           physical and logical geometry
                  identify           in hexadecimal
                  media              media type
                  model              manufacturer's model number
                  settings           drive settings
                  smart_thresholds   in hexadecimal
                  smart_values       in hexadecimal

              The hdparm(8) utility provides access to this information  in  a
              friendly format.

       /proc/interrupts
              This  is  used to record the number of interrupts per CPU per IO
              device.  Since Linux 2.6.24, for the i386 and  x86_64  architec-
              tures,  at  least, this also includes interrupts internal to the
              system (that is, not associated with a device as such), such  as
              NMI  (nonmaskable  interrupt),  LOC (local timer interrupt), and
              for SMP systems, TLB (TLB flush  interrupt),  RES  (rescheduling
              interrupt),  CAL  (remote function call interrupt), and possibly
              others.  Very easy to read formatting, done in ASCII.

       /proc/iomem
              I/O memory map in Linux 2.4.

       /proc/ioports
              This is a list of currently registered Input-Output port regions
              that are in use.

       /proc/kallsyms (since Linux 2.5.71)
              This  holds  the  kernel exported symbol definitions used by the
              modules(X) tools to dynamically link and bind loadable  modules.
              In  Linux  2.5.47 and earlier, a similar file with slightly dif-
              ferent syntax was named ksyms.

       /proc/kcore
              This file represents the physical memory of the  system  and  is
              stored  in the ELF core file format.  With this pseudo-file, and
              an unstripped kernel (/usr/src/linux/vmlinux) binary, GDB can be
              used to examine the current state of any kernel data structures.

              The  total  length  of  the  file is the size of physical memory
              (RAM) plus 4 KiB.

       /proc/keys (since Linux 2.6.10)
              See keyrings(7).

       /proc/key-users (since Linux 2.6.10)
              See keyrings(7).

       /proc/kmsg
              This file can be used instead of the syslog(2)  system  call  to
              read  kernel messages.  A process must have superuser privileges
              to read this file, and only one process should read  this  file.
              This  file  should  not  be  read if a syslog process is running
              which uses the syslog(2) system call facility to log kernel mes-
              sages.

              Information in this file is retrieved with the dmesg(1) program.

       /proc/kpagecount (since Linux 2.6.25)
              This  file  contains  a 64-bit count of the number of times each
              physical page frame is mapped, indexed by page frame number (see
              the discussion of /proc/[pid]/pagemap).

              The   /proc/kpagecount   file   is  present  only  if  the  CON-
              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/kpageflags (since Linux 2.6.25)
              This file contains 64-bit masks corresponding to  each  physical
              page  frame; it is indexed by page frame number (see the discus-
              sion of /proc/[pid]/pagemap).  The bits are as follows:

                   0 - KPF_LOCKED
                   1 - KPF_ERROR
                   2 - KPF_REFERENCED
                   3 - KPF_UPTODATE
                   4 - KPF_DIRTY
                   5 - KPF_LRU
                   6 - KPF_ACTIVE
                   7 - KPF_SLAB
                   8 - KPF_WRITEBACK
                   9 - KPF_RECLAIM
                  10 - KPF_BUDDY
                  11 - KPF_MMAP           (since Linux 2.6.31)
                  12 - KPF_ANON           (since Linux 2.6.31)
                  13 - KPF_SWAPCACHE      (since Linux 2.6.31)
                  14 - KPF_SWAPBACKED     (since Linux 2.6.31)
                  15 - KPF_COMPOUND_HEAD  (since Linux 2.6.31)
                  16 - KPF_COMPOUND_TAIL  (since Linux 2.6.31)
                  16 - KPF_HUGE           (since Linux 2.6.31)
                  18 - KPF_UNEVICTABLE    (since Linux 2.6.31)
                  19 - KPF_HWPOISON       (since Linux 2.6.31)
                  20 - KPF_NOPAGE         (since Linux 2.6.31)
                  21 - KPF_KSM            (since Linux 2.6.32)
                  22 - KPF_THP            (since Linux 3.4)

              For further details on the meanings of these bits, see the  ker-
              nel  source  file  Documentation/vm/pagemap.txt.   Before kernel
              2.6.29, KPF_WRITEBACK, KPF_RECLAIM,  KPF_BUDDY,  and  KPF_LOCKED
              did not report correctly.

              The   /proc/kpageflags   file   is  present  only  if  the  CON-
              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/ksyms (Linux 1.1.23-2.5.47)
              See /proc/kallsyms.

       /proc/loadavg
              The first three fields in this file  are  load  average  figures
              giving  the number of jobs in the run queue (state R) or waiting
              for disk I/O (state D) averaged over 1, 5, and 15 minutes.  They
              are  the same as the load average numbers given by uptime(1) and
              other programs.  The fourth field consists of two numbers  sepa-
              rated  by a slash (/).  The first of these is the number of cur-
              rently runnable kernel scheduling entities (processes, threads).
              The  value  after  the  slash is the number of kernel scheduling
              entities that currently exist on the system.  The fifth field is
              the  PID  of  the  process that was most recently created on the
              system.

       /proc/locks
              This file shows current file locks (flock(2) and  fcntl(2))  and
              leases  (fcntl(2)).   The lslocks(8) command provides a bit more
              information about each lock.

       /proc/malloc (only up to and including Linux 2.2)
              This file is present only  if  CONFIG_DEBUG_MALLOC  was  defined
              during compilation.

       /proc/meminfo
              This  file  reports statistics about memory usage on the system.
              It is used by free(1) to report the amount of free and used mem-
              ory (both physical and swap) on the system as well as the shared
              memory and buffers used by the kernel.  Each line  of  the  file
              consists  of a parameter name, followed by a colon, the value of
              the parameter, and an option unit of measurement  (e.g.,  "kB").
              The  list  below  describes  the  parameter names and the format
              specifier required to read the field  value.   Except  as  noted
              below,  all of the fields have been present since at least Linux
              2.6.0.  Some fields are displayed only if the kernel was config-
              ured  with  various options; those dependencies are noted in the
              list.

              MemTotal %lu
                     Total usable RAM (i.e., physical RAM minus a few reserved
                     bits and the kernel binary code).

              MemFree %lu
                     The sum of LowFree+HighFree.

              MemAvailable %lu (since Linux 3.14)
                     An  estimate of how much memory is available for starting
                     new applications, without swapping.

              Buffers %lu
                     Relatively temporary storage for  raw  disk  blocks  that
                     shouldn't get tremendously large (20MB or so).

              Cached %lu
                     In-memory  cache  for  files read from the disk (the page
                     cache).  Doesn't include SwapCached.

              SwapCached %lu
                     Memory that once was swapped out, is swapped back in  but
                     still  also  is in the swap file.  (If memory pressure is
                     high, these pages don't need  to  be  swapped  out  again
                     because  they  are  already in the swap file.  This saves
                     I/O.)

              Active %lu
                     Memory that has been used more recently and  usually  not
                     reclaimed unless absolutely necessary.

              Inactive %lu
                     Memory  which  has  been  less recently used.  It is more
                     eligible to be reclaimed for other purposes.

              Active(anon) %lu (since Linux 2.6.28)
                     [To be documented.]

              Inactive(anon) %lu (since Linux 2.6.28)
                     [To be documented.]

              Active(file) %lu (since Linux 2.6.28)
                     [To be documented.]

              Inactive(file) %lu (since Linux 2.6.28)
                     [To be documented.]

              Unevictable %lu (since Linux 2.6.28)
                     (From Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU  was
                     required.)  [To be documented.]

              Mlocked %lu (since Linux 2.6.28)
                     (From  Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU was
                     required.)  [To be documented.]

              HighTotal %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
                     Total  amount  of  highmem.   Highmem is all memory above
                     ~860MB of physical memory.  Highmem areas are for use  by
                     user-space  programs,  or for the page cache.  The kernel
                     must use tricks to access this memory, making  it  slower
                     to access than lowmem.

              HighFree %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
                     Amount of free highmem.

              LowTotal %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
                     Total  amount  of  lowmem.  Lowmem is memory which can be
                     used for everything that highmem can be used for, but  it
                     is  also  available for the kernel's use for its own data
                     structures.  Among many other things, it is where  every-
                     thing  from  Slab  is  allocated.  Bad things happen when
                     you're out of lowmem.

              LowFree %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
                     Amount of free lowmem.

              MmapCopy %lu (since Linux 2.6.29)
                     (CONFIG_MMU is required.)  [To be documented.]

              SwapTotal %lu
                     Total amount of swap space available.

              SwapFree %lu
                     Amount of swap space that is currently unused.

              Dirty %lu
                     Memory which is waiting to get written back to the disk.

              Writeback %lu
                     Memory which is actively being written back to the disk.

              AnonPages %lu (since Linux 2.6.18)
                     Non-file backed pages mapped into user-space page tables.

              Mapped %lu
                     Files  which have been mapped into memory (with mmap(2)),
                     such as libraries.

              Shmem %lu (since Linux 2.6.32)
                     Amount of memory consumed in tmpfs(5) filesystems.

              Slab %lu
                     In-kernel data structures cache.  (See slabinfo(5).)

              SReclaimable %lu (since Linux 2.6.19)
                     Part of Slab, that might be reclaimed, such as caches.

              SUnreclaim %lu (since Linux 2.6.19)
                     Part of Slab, that cannot be reclaimed  on  memory  pres-
                     sure.

              KernelStack %lu (since Linux 2.6.32)
                     Amount of memory allocated to kernel stacks.

              PageTables %lu (since Linux 2.6.18)
                     Amount  of  memory  dedicated to the lowest level of page
                     tables.

              Quicklists %lu (since Linux 2.6.27)
                     (CONFIG_QUICKLIST is required.)  [To be documented.]

              NFS_Unstable %lu (since Linux 2.6.18)
                     NFS pages sent to the server, but not  yet  committed  to
                     stable storage.

              Bounce %lu (since Linux 2.6.18)
                     Memory used for block device "bounce buffers".

              WritebackTmp %lu (since Linux 2.6.26)
                     Memory used by FUSE for temporary writeback buffers.

              CommitLimit %lu (since Linux 2.6.10)
                     This is the total amount of memory currently available to
                     be allocated on the system, expressed in kilobytes.  This
                     limit  is adhered to only if strict overcommit accounting
                     is enabled (mode  2  in  /proc/sys/vm/overcommit_memory).
                     The   limit   is  calculated  according  to  the  formula
                     described under /proc/sys/vm/overcommit_memory.  For fur-
                     ther  details,  see  the  kernel  source  file Documenta-
                     tion/vm/overcommit-accounting.

              Committed_AS %lu
                     The amount of memory presently allocated on  the  system.
                     The  committed memory is a sum of all of the memory which
                     has been allocated by processes, even if it has not  been
                     "used"  by them as of yet.  A process which allocates 1GB
                     of memory (using malloc(3) or similar), but touches  only
                     300MB  of that memory will show up as using only 300MB of
                     memory even if it has the address space allocated for the
                     entire 1GB.

                     This  1GB  is memory which has been "committed" to by the
                     VM and can be used at any time by the allocating applica-
                     tion.  With strict overcommit enabled on the system (mode
                     2 in /proc/sys/vm/overcommit_memory),  allocations  which
                     would exceed the CommitLimit will not be permitted.  This
                     is useful if one needs to guarantee that  processes  will
                     not  fail due to lack of memory once that memory has been
                     successfully allocated.

              VmallocTotal %lu
                     Total size of vmalloc memory area.

              VmallocUsed %lu
                     Amount of vmalloc area which is used.

              VmallocChunk %lu
                     Largest contiguous block of vmalloc area which is free.

              HardwareCorrupted %lu (since Linux 2.6.32)
                     (CONFIG_MEMORY_FAILURE is required.)  [To be documented.]

              AnonHugePages %lu (since Linux 2.6.38)
                     (CONFIG_TRANSPARENT_HUGEPAGE  is   required.)    Non-file
                     backed huge pages mapped into user-space page tables.

              ShmemHugePages %lu (since Linux 4.8)
                     (CONFIG_TRANSPARENT_HUGEPAGE  is  required.)  Memory used
                     by shared memory (shmem) and tmpfs(5) allocated with huge
                     pages

              ShmemPmdMapped %lu (since Linux 4.8)
                     (CONFIG_TRANSPARENT_HUGEPAGE is required.)  Shared memory
                     mapped into user space with huge pages.

              CmaTotal %lu (since Linux 3.1)
                     Total CMA (Contiguous  Memory  Allocator)  pages.   (CON-
                     FIG_CMA is required.)

              CmaFree %lu (since Linux 3.1)
                     Free  CMA  (Contiguous  Memory  Allocator)  pages.  (CON-
                     FIG_CMA is required.)

              HugePages_Total %lu
                     (CONFIG_HUGETLB_PAGE is required.)  The size of the  pool
                     of huge pages.

              HugePages_Free %lu
                     (CONFIG_HUGETLB_PAGE  is  required.)   The number of huge
                     pages in the pool that are not yet allocated.

              HugePages_Rsvd %lu (since Linux 2.6.17)
                     (CONFIG_HUGETLB_PAGE is required.)  This is the number of
                     huge  pages  for  which a commitment to allocate from the
                     pool has been made, but no allocation has yet been  made.
                     These  reserved  huge pages guarantee that an application
                     will be able to allocate a huge page  from  the  pool  of
                     huge pages at fault time.

              HugePages_Surp %lu (since Linux 2.6.24)
                     (CONFIG_HUGETLB_PAGE is required.)  This is the number of
                     huge   pages   in   the   pool   above   the   value   in
                     /proc/sys/vm/nr_hugepages.  The maximum number of surplus
                     huge  pages  is  controlled  by  /proc/sys/vm/nr_overcom-
                     mit_hugepages.

              Hugepagesize %lu
                     (CONFIG_HUGETLB_PAGE  is  required.)   The  size  of huge
                     pages.

              DirectMap4k %lu (since Linux 2.6.27)
                     Number of bytes of RAM linearly mapped by kernel  in  4kB
                     pages.  (x86.)

              DirectMap4M %lu (since Linux 2.6.27)
                     Number  of  bytes of RAM linearly mapped by kernel in 4MB
                     pages.   (x86  with   CONFIG_X86_64   or   CONFIG_X86_PAE
                     enabled.)

              DirectMap2M %lu (since Linux 2.6.27)
                     Number  of  bytes of RAM linearly mapped by kernel in 2MB
                     pages.   (x86  with  neither   CONFIG_X86_64   nor   CON-
                     FIG_X86_PAE enabled.)

              DirectMap1G %lu (since Linux 2.6.27)
                     (x86  with  CONFIG_X86_64  and  CONFIG_X86_DIRECT_GBPAGES
                     enabled.)

       /proc/modules
              A text list of the modules that have been loaded by the  system.
              See also lsmod(8).

       /proc/mounts
              Before  kernel  2.4.19, this file was a list of all the filesys-
              tems currently mounted on the system.  With the introduction  of
              per-process  mount  namespaces in Linux 2.4.19 (see mount_names-
              paces(7)), this file became a link to  /proc/self/mounts,  which
              lists  the  mount  points  of the process's own mount namespace.
              The format of this file is documented in fstab(5).

       /proc/mtrr
              Memory Type Range Registers.  See the Linux kernel  source  file
              Documentation/x86/mtrr.txt   (or  Documentation/mtrr.txt  before
              Linux 2.6.28) for details.

       /proc/net
              This directory contains various files  and  subdirectories  con-
              taining  information about the networking layer.  The files con-
              tain ASCII structures and are, therefore, readable with  cat(1).
              However,  the  standard  netstat(8)  suite provides much cleaner
              access to these files.

              With the  advent  of  network  namespaces,  various  information
              relating  to  the  network  stack  is  virtualized  (see  names-
              paces(7)).  Thus, since Linux 2.6.25, /proc/net  is  a  symbolic
              link  to  the  directory /proc/self/net, which contains the same
              files and directories as listed below.  However, these files and
              directories  now expose information for the network namespace of
              which the process is a member.

       /proc/net/arp
              This holds an ASCII readable dump of the kernel ARP  table  used
              for  address resolutions.  It will show both dynamically learned
              and preprogrammed ARP entries.  The format is:

       IP address     HW type   Flags     HW address          Mask   Device
       192.168.0.50   0x1       0x2       00:50:BF:25:68:F3   *      eth0
       192.168.0.250  0x1       0xc       00:00:00:00:00:00   *      eth0

              Here "IP address" is the IPv4 address of the machine and the "HW
              type"  is  the  hardware  type of the address from RFC 826.  The
              flags are the internal flags of the ARP structure (as defined in
              /usr/include/linux/if_arp.h)  and  the  "HW address" is the data
              link layer mapping for that IP address if it is known.

       /proc/net/dev
              The dev pseudo-file contains network device status  information.
              This  gives  the number of received and sent packets, the number
              of errors and collisions and other basic statistics.  These  are
              used  by  the  ifconfig(8) program to report device status.  The
              format is:

 Inter-|   Receive                                                |  Transmit
  face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
     lo: 2776770   11307    0    0    0     0          0         0  2776770   11307    0    0    0     0       0          0
   eth0: 1215645    2751    0    0    0     0          0         0  1782404    4324    0    0    0   427       0          0
   ppp0: 1622270    5552    1    0    0     0          0         0   354130    5669    0    0    0     0       0          0
   tap0:    7714      81    0    0    0     0          0         0     7714      81    0    0    0     0       0          0

       /proc/net/dev_mcast
              Defined in /usr/src/linux/net/core/dev_mcast.c:

                  indx interface_name  dmi_u dmi_g dmi_address
                  2    eth0            1     0     01005e000001
                  3    eth1            1     0     01005e000001
                  4    eth2            1     0     01005e000001

       /proc/net/igmp
              Internet    Group    Management    Protocol.      Defined     in
              /usr/src/linux/net/core/igmp.c.

       /proc/net/rarp
              This  file uses the same format as the arp file and contains the
              current reverse mapping database used to provide rarp(8) reverse
              address  lookup  services.   If  RARP is not configured into the
              kernel, this file will not be present.

       /proc/net/raw
              Holds a dump of the RAW socket table.  Much of  the  information
              is  not of use apart from debugging.  The "sl" value is the ker-
              nel hash slot for the socket, the "local_address" is  the  local
              address  and  protocol number pair.  "St" is the internal status
              of the socket.  The "tx_queue" and "rx_queue" are  the  outgoing
              and  incoming  data  queue in terms of kernel memory usage.  The
              "tr", "tm->when", and "rexmits" fields are not used by RAW.  The
              "uid"  field  holds  the  effective  UID  of  the creator of the
              socket.

       /proc/net/snmp
              This file holds the ASCII data needed for the IP, ICMP, TCP, and
              UDP management information bases for an SNMP agent.

       /proc/net/tcp
              Holds  a  dump of the TCP socket table.  Much of the information
              is not of use apart from debugging.  The "sl" value is the  ker-
              nel  hash  slot for the socket, the "local_address" is the local
              address and port number pair.  The "rem_address" is  the  remote
              address and port number pair (if connected).  "St" is the inter-
              nal status of the socket.  The "tx_queue" and "rx_queue" are the
              outgoing  and  incoming  data  queue  in  terms of kernel memory
              usage.  The "tr", "tm->when", and "rexmits" fields hold internal
              information  of  the kernel socket state and are useful only for
              debugging.  The "uid" field holds the effective UID of the  cre-
              ator of the socket.

       /proc/net/udp
              Holds  a  dump of the UDP socket table.  Much of the information
              is not of use apart from debugging.  The "sl" value is the  ker-
              nel  hash  slot for the socket, the "local_address" is the local
              address and port number pair.  The "rem_address" is  the  remote
              address and port number pair (if connected).  "St" is the inter-
              nal status of the socket.  The "tx_queue" and "rx_queue" are the
              outgoing  and  incoming  data  queue  in  terms of kernel memory
              usage.  The "tr", "tm->when", and "rexmits" fields are not  used
              by  UDP.  The "uid" field holds the effective UID of the creator
              of the socket.  The format is:

 sl  local_address rem_address   st tx_queue rx_queue tr rexmits  tm->when uid
  1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0
  1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0
  1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0

       /proc/net/unix
              Lists the UNIX domain sockets  present  within  the  system  and
              their status.  The format is:

 Num RefCount Protocol Flags    Type St Path
  0: 00000002 00000000 00000000 0001 03
  1: 00000001 00000000 00010000 0001 01 /dev/printer

              The fields are as follows:

              Num:      the kernel table slot number.

              RefCount: the number of users of the socket.

              Protocol: currently always 0.

              Flags:    the  internal  kernel  flags holding the status of the
                        socket.

              Type:     the socket type.  For  SOCK_STREAM  sockets,  this  is
                        0001;  for  SOCK_DGRAM  sockets,  it  is 0002; and for
                        SOCK_SEQPACKET sockets, it is 0005.

              St:       the internal state of the socket.

              Path:     the bound path (if any) of the socket.  Sockets in the
                        abstract  namespace  are included in the list, and are
                        shown with a Path that commences  with  the  character
                        '@'.

       /proc/net/netfilter/nfnetlink_queue
              This file contains information about netfilter user-space queue-
              ing, if used.  Each line represents a queue.  Queues  that  have
              not been subscribed to by user space are not shown.

                     1   4207     0  2 65535     0     0        0  1
                    (1)   (2)    (3)(4)  (5)    (6)   (7)      (8)

              The fields in each line are:

              (1)  The ID of the queue.  This matches what is specified in the
                   --queue-num or --queue-balance options to  the  iptables(8)
                   NFQUEUE target.  See iptables-extensions(8) for more infor-
                   mation.

              (2)  The netlink port ID subscribed to the queue.

              (3)  The number of packets currently queued and  waiting  to  be
                   processed by the application.

              (4)  The copy mode of the queue.  It is either 1 (metadata only)
                   or 2 (also copy payload data to user space).

              (5)  Copy range; that is,  how  many  bytes  of  packet  payload
                   should be copied to user space at most.

              (6)  queue dropped.  Number of packets that had to be dropped by
                   the kernel because too many packets are already waiting for
                   user space to send back the mandatory accept/drop verdicts.

              (7)  queue  user  dropped.   Number of packets that were dropped
                   within the netlink subsystem.  Such  drops  usually  happen
                   when the corresponding socket buffer is full; that is, user
                   space is not able to read messages fast enough.

              (8)  sequence number.  Every queued packet is associated with  a
                   (32-bit)  monotonically-increasing  sequence  number.  This
                   shows the ID of the most recent packet queued.

              The last number exists only for  compatibility  reasons  and  is
              always 1.

       /proc/partitions
              Contains  the  major and minor numbers of each partition as well
              as the number of 1024-byte blocks and the partition name.

       /proc/pci
              This is a listing of all PCI devices found  during  kernel  ini-
              tialization and their configuration.

              This  file has been deprecated in favor of a new /proc interface
              for PCI  (/proc/bus/pci).   It  became  optional  in  Linux  2.2
              (available  with CONFIG_PCI_OLD_PROC set at kernel compilation).
              It became once more nonoptionally enabled in Linux  2.4.   Next,
              it  was  deprecated  in  Linux  2.6  (still  available with CON-
              FIG_PCI_LEGACY_PROC set), and finally removed  altogether  since
              Linux 2.6.17.

       /proc/profile (since Linux 2.4)
              This file is present only if the kernel was booted with the pro-
              file=1 command-line option.  It exposes kernel profiling  infor-
              mation  in  a  binary format for use by readprofile(1).  Writing
              (e.g., an empty string) to this file resets the profiling  coun-
              ters; on some architectures, writing a binary integer "profiling
              multiplier" of size sizeof(int)  sets  the  profiling  interrupt
              frequency.

       /proc/scsi
              A directory with the scsi mid-level pseudo-file and various SCSI
              low-level driver directories, which contain a file for each SCSI
              host  in  this system, all of which give the status of some part
              of the SCSI IO subsystem.  These files contain ASCII  structures
              and are, therefore, readable with cat(1).

              You  can also write to some of the files to reconfigure the sub-
              system or switch certain features on or off.

       /proc/scsi/scsi
              This is a listing of all SCSI devices known to the kernel.   The
              listing  is  similar  to  the one seen during bootup.  scsi cur-
              rently supports only the add-single-device command which  allows
              root to add a hotplugged device to the list of known devices.

              The command

                  echo 'scsi add-single-device 1 0 5 0' > /proc/scsi/scsi

              will  cause host scsi1 to scan on SCSI channel 0 for a device on
              ID 5 LUN 0.  If there is already a device known on this  address
              or the address is invalid, an error will be returned.

       /proc/scsi/[drivername]
              [drivername]  can  currently  be  NCR53c7xx,  aha152x,  aha1542,
              aha1740, aic7xxx, buslogic, eata_dma, eata_pio, fdomain, in2000,
              pas16,  qlogic,  scsi_debug, seagate, t128, u15-24f, ultrastore,
              or wd7000.  These directories show up for all drivers that  reg-
              istered  at  least  one  SCSI HBA.  Every directory contains one
              file per registered host.  Every host-file is  named  after  the
              number the host was assigned during initialization.

              Reading these files will usually show driver and host configura-
              tion, statistics, and so on.

              Writing to these files  allows  different  things  on  different
              hosts.   For  example,  with the latency and nolatency commands,
              root can switch on and off command latency measurement  code  in
              the  eata_dma driver.  With the lockup and unlock commands, root
              can control bus lockups simulated by the scsi_debug driver.

       /proc/self
              This  directory  refers  to  the  process  accessing  the  /proc
              filesystem, and is identical to the /proc directory named by the
              process ID of the same process.

       /proc/slabinfo
              Information about kernel caches.  See slabinfo(5) for details.

       /proc/stat
              kernel/system statistics.   Varies  with  architecture.   Common
              entries include:

              cpu 10132153 290696 3084719 46828483 16683 0 25195 0 175628 0
              cpu0 1393280 32966 572056 13343292 6130 0 17875 0 23933 0
                     The   amount  of  time,  measured  in  units  of  USER_HZ
                     (1/100ths  of  a  second  on  most   architectures,   use
                     sysconf(_SC_CLK_TCK) to obtain the right value), that the
                     system ("cpu" line) or the  specific  CPU  ("cpuN"  line)
                     spent in various states:

                     user   (1) Time spent in user mode.

                     nice   (2)  Time  spent  in  user  mode with low priority
                            (nice).

                     system (3) Time spent in system mode.

                     idle   (4) Time spent  in  the  idle  task.   This  value
                            should  be  USER_HZ  times the second entry in the
                            /proc/uptime pseudo-file.

                     iowait (since Linux 2.5.41)
                            (5) Time waiting for I/O to complete.  This  value
                            is not reliable, for the following reasons:

                            1. The  CPU  will  not  wait  for I/O to complete;
                               iowait is the time that a task is  waiting  for
                               I/O  to  complete.   When  a CPU goes into idle
                               state for outstanding task  I/O,  another  task
                               will be scheduled on this CPU.

                            2. On  a  multi-core CPU, the task waiting for I/O
                               to complete is not running on any CPU,  so  the
                               iowait of each CPU is difficult to calculate.

                            3. The value in this field may decrease in certain
                               conditions.

                     irq (since Linux 2.6.0-test4)
                            (6) Time servicing interrupts.

                     softirq (since Linux 2.6.0-test4)
                            (7) Time servicing softirqs.

                     steal (since Linux 2.6.11)
                            (8) Stolen time, which is the time spent in  other
                            operating  systems  when  running in a virtualized
                            environment

                     guest (since Linux 2.6.24)
                            (9) Time spent running a  virtual  CPU  for  guest
                            operating  systems  under the control of the Linux
                            kernel.

                     guest_nice (since Linux 2.6.33)
                            (10) Time spent running a niced guest (virtual CPU
                            for  guest  operating systems under the control of
                            the Linux kernel).

              page 5741 1808
                     The number of pages the system paged in  and  the  number
                     that were paged out (from disk).

              swap 1 0
                     The  number  of  swap pages that have been brought in and
                     out.

              intr 1462898
                     This line shows counts of interrupts serviced since  boot
                     time,  for  each  of the possible system interrupts.  The
                     first column is the  total  of  all  interrupts  serviced
                     including  unnumbered  architecture  specific interrupts;
                     each subsequent column is the total for  that  particular
                     numbered interrupt.  Unnumbered interrupts are not shown,
                     only summed into the total.

              disk_io: (2,0):(31,30,5764,1,2) (3,0):...
                     (major,disk_idx):(noinfo,     read_io_ops,     blks_read,
                     write_io_ops, blks_written)
                     (Linux 2.4 only)

              ctxt 115315
                     The number of context switches that the system underwent.

              btime 769041601
                     boot   time,  in  seconds  since  the  Epoch,  1970-01-01
                     00:00:00 +0000 (UTC).

              processes 86031
                     Number of forks since boot.

              procs_running 6
                     Number of processes in  runnable  state.   (Linux  2.5.45
                     onward.)

              procs_blocked 2
                     Number  of processes blocked waiting for I/O to complete.
                     (Linux 2.5.45 onward.)

              softirq 229245889 94 60001584 13619 5175704 2471304 28  51212741
              59130143 0 51240672
                     This  line shows the number of softirq for all CPUs.  The
                     first column is the total of all softirqs and each subse-
                     quent column is the total for particular softirq.  (Linux
                     2.6.31 onward.)

       /proc/swaps
              Swap areas in use.  See also swapon(8).

       /proc/sys
              This directory (present since 1.3.57) contains a number of files
              and  subdirectories  corresponding  to  kernel variables.  These
              variables can be read and sometimes  modified  using  the  /proc
              filesystem, and the (deprecated) sysctl(2) system call.

              String values may be terminated by either '\0' or '\n'.

              Integer  and  long values may be written either in decimal or in
              hexadecimal notation (e.g. 0x3FFF).  When writing multiple inte-
              ger or long values, these may be separated by any of the follow-
              ing whitespace characters: ' ', '\t', or '\n'.  Using other sep-
              arators leads to the error EINVAL.

       /proc/sys/abi (since Linux 2.4.10)
              This  directory may contain files with application binary infor-
              mation.   See  the   Linux   kernel   source   file   Documenta-
              tion/sysctl/abi.txt for more information.

       /proc/sys/debug
              This directory may be empty.

       /proc/sys/dev
              This   directory  contains  device-specific  information  (e.g.,
              dev/cdrom/info).  On some systems, it may be empty.

       /proc/sys/fs
              This directory contains the files and subdirectories for  kernel
              variables related to filesystems.

       /proc/sys/fs/binfmt_misc
              Documentation  for  files  in this directory can be found in the
              Linux   kernel   source   in   the   file   Documentation/admin-
              guide/binfmt-misc.rst  (or  in  Documentation/binfmt_misc.txt on
              older kernels).

       /proc/sys/fs/dentry-state (since Linux 2.2)
              This file contains information about the status of the directory
              cache  (dcache).   The  file  contains  six  numbers, nr_dentry,
              nr_unused,  age_limit  (age  in  seconds),   want_pages   (pages
              requested by system) and two dummy values.

              * nr_dentry   is   the  number  of  allocated  dentries  (dcache
                entries).  This field is unused in Linux 2.2.

              * nr_unused is the number of unused dentries.

              * age_limit is the age in seconds after which dcache entries can
                be reclaimed when memory is short.

              * want_pages   is   nonzero   when   the   kernel   has   called
                shrink_dcache_pages() and the dcache isn't pruned yet.

       /proc/sys/fs/dir-notify-enable
              This file can be used to disable or enable the dnotify interface
              described  in  fcntl(2) on a system-wide basis.  A value of 0 in
              this file disables the interface, and a value of 1 enables it.

       /proc/sys/fs/dquot-max
              This file shows the maximum number of cached disk quota entries.
              On some (2.4) systems, it is not present.  If the number of free
              cached disk quota entries is very low and you have some  awesome
              number of simultaneous system users, you might want to raise the
              limit.

       /proc/sys/fs/dquot-nr
              This file shows the number of allocated disk quota  entries  and
              the number of free disk quota entries.

       /proc/sys/fs/epoll (since Linux 2.6.28)
              This  directory contains the file max_user_watches, which can be
              used to limit the amount of kernel memory consumed by the  epoll
              interface.  For further details, see epoll(7).

       /proc/sys/fs/file-max
              This  file  defines  a  system-wide  limit on the number of open
              files for all processes.  System calls that fail when encounter-
              ing  this  limit  fail  with  the error ENFILE.  (See also setr-
              limit(2), which can be used by a process to set the  per-process
              limit,  RLIMIT_NOFILE,  on the number of files it may open.)  If
              you get lots of error messages in the kernel log  about  running
              out  of  file  handles  (look  for "VFS: file-max limit <number>
              reached"), try increasing this value:

                  echo 100000 > /proc/sys/fs/file-max

              Privileged processes (CAP_SYS_ADMIN) can override  the  file-max
              limit.

       /proc/sys/fs/file-nr
              This  (read-only)  file  contains  three  numbers: the number of
              allocated file handles (i.e.,  the  number  of  files  presently
              opened); the number of free file handles; and the maximum number
              of file handles (i.e., the same value as /proc/sys/fs/file-max).
              If the number of allocated file handles is close to the maximum,
              you should consider increasing the maximum.  Before  Linux  2.6,
              the  kernel  allocated  file  handles dynamically, but it didn't
              free them again.  Instead the free file handles were kept  in  a
              list  for  reallocation; the "free file handles" value indicates
              the size of that list.  A large  number  of  free  file  handles
              indicates  that  there was a past peak in the usage of open file
              handles.  Since Linux 2.6, the kernel does deallocate freed file
              handles, and the "free file handles" value is always zero.

       /proc/sys/fs/inode-max (only present until Linux 2.2)
              This file contains the maximum number of in-memory inodes.  This
              value should be 3-4 times larger than  the  value  in  file-max,
              since  stdin,  stdout  and network sockets also need an inode to
              handle them.  When you regularly run out of inodes, you need  to
              increase this value.

              Starting  with  Linux  2.4, there is no longer a static limit on
              the number of inodes, and this file is removed.

       /proc/sys/fs/inode-nr
              This file contains the first two values from inode-state.

       /proc/sys/fs/inode-state
              This file contains  seven  numbers:  nr_inodes,  nr_free_inodes,
              preshrink, and four dummy values (always zero).

              nr_inodes  is  the  number  of  inodes the system has allocated.
              nr_free_inodes represents the number of free inodes.

              preshrink is nonzero when the nr_inodes > inode-max and the sys-
              tem  needs  to  prune the inode list instead of allocating more;
              since Linux 2.4, this field is a dummy value (always zero).

       /proc/sys/fs/inotify (since Linux 2.6.13)
              This     directory     contains     files     max_queued_events,
              max_user_instances,  and  max_user_watches,  that can be used to
              limit the amount of kernel memory consumed by the inotify inter-
              face.  For further details, see inotify(7).

       /proc/sys/fs/lease-break-time
              This file specifies the grace period that the kernel grants to a
              process holding a file lease (fcntl(2)) after it has sent a sig-
              nal to that process notifying it that another process is waiting
              to open the file.  If the lease holder does not remove or  down-
              grade  the  lease  within this grace period, the kernel forcibly
              breaks the lease.

       /proc/sys/fs/leases-enable
              This  file  can  be  used  to  enable  or  disable  file  leases
              (fcntl(2))  on  a  system-wide basis.  If this file contains the
              value 0, leases are disabled.  A nonzero value enables leases.

       /proc/sys/fs/mount-max (since Linux 4.9)
              The value in this file specifies the maximum  number  of  mounts
              that  may exist in a mount namespace.  The default value in this
              file is 100,000.

       /proc/sys/fs/mqueue (since Linux 2.6.6)
              This  directory  contains  files   msg_max,   msgsize_max,   and
              queues_max,  controlling  the  resources  used  by POSIX message
              queues.  See mq_overview(7) for details.

       /proc/sys/fs/nr_open (since Linux 2.6.25)
              This  file  imposes  ceiling  on  the   value   to   which   the
              RLIMIT_NOFILE  resource  limit can be raised (see getrlimit(2)).
              This ceiling is enforced for both  unprivileged  and  privileged
              process.   The  default  value in this file is 1048576.  (Before
              Linux 2.6.25, the ceiling for RLIMIT_NOFILE  was  hard-coded  to
              the same value.)

       /proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid
              These  files  allow you to change the value of the fixed UID and
              GID.  The default  is  65534.   Some  filesystems  support  only
              16-bit  UIDs  and  GIDs,  although in Linux UIDs and GIDs are 32
              bits.  When one of these  filesystems  is  mounted  with  writes
              enabled, any UID or GID that would exceed 65535 is translated to
              the overflow value before being written to disk.

       /proc/sys/fs/pipe-max-size (since Linux 2.6.35)
              See pipe(7).

       /proc/sys/fs/pipe-user-pages-hard (since Linux 4.5)
              See pipe(7).

       /proc/sys/fs/pipe-user-pages-soft (since Linux 4.5)
              See pipe(7).

       /proc/sys/fs/protected_hardlinks (since Linux 3.6)
              When the value in this file is 0, no restrictions are placed  on
              the  creation of hard links (i.e., this is the historical behav-
              ior before Linux 3.6).  When the value in this file is 1, a hard
              link  can be created to a target file only if one of the follow-
              ing conditions is true:

              *  The calling process has the CAP_FOWNER capability in its user
                 namespace and the file UID has a mapping in the namespace.

              *  The  filesystem  UID of the process creating the link matches
                 the owner (UID) of the target file (as described  in  creden-
                 tials(7),  a process's filesystem UID is normally the same as
                 its effective UID).

              *  All of the following conditions are true:

                  o  the target is a regular file;

                  o  the target file does not have its  set-user-ID  mode  bit
                     enabled;

                  o  the  target  file does not have both its set-group-ID and
                     group-executable mode bits enabled; and

                  o  the caller has permission to read and  write  the  target
                     file  (either  via the file's permissions mask or because
                     it has suitable capabilities).

              The default value in this file is 0.  Setting  the  value  to  1
              prevents a longstanding class of security issues caused by hard-
              link-based time-of-check, time-of-use races, most commonly  seen
              in  world-writable  directories such as /tmp.  The common method
              of exploiting this flaw is to cross  privilege  boundaries  when
              following a given hard link (i.e., a root process follows a hard
              link created by another user).  Additionally, on systems without
              separated  partitions,  this stops unauthorized users from "pin-
              ning" vulnerable  set-user-ID  and  set-group-ID  files  against
              being  upgraded  by  the  administrator,  or  linking to special
              files.

       /proc/sys/fs/protected_symlinks (since Linux 3.6)
              When the value in this file is 0, no restrictions are placed  on
              following  symbolic links (i.e., this is the historical behavior
              before Linux 3.6).  When the value in this file is  1,  symbolic
              links are followed only in the following circumstances:

              *  the  filesystem UID of the process following the link matches
                 the owner (UID) of the symbolic link (as described in creden-
                 tials(7),  a process's filesystem UID is normally the same as
                 its effective UID);

              *  the link is not in a sticky world-writable directory; or

              *  the symbolic link and its  parent  directory  have  the  same
                 owner (UID)

              A  system  call  that fails to follow a symbolic link because of
              the above restrictions returns the error EACCES in errno.

              The default value in this file is 0.  Setting  the  value  to  1
              avoids a longstanding class of security issues based on time-of-
              check, time-of-use races when accessing symbolic links.

       /proc/sys/fs/suid_dumpable (since Linux 2.6.13)
              The value in this file is assigned  to  a  process's  "dumpable"
              flag in the circumstances described in prctl(2).  In effect, the
              value in this file determines whether core dump files  are  pro-
              duced  for  set-user-ID or otherwise protected/tainted binaries.
              The "dumpable" setting also affects the ownership of files in  a
              process's /proc/[pid] directory, as described above.

              Three different integer values can be specified:

              0 (default)
                     This  provides  the traditional (pre-Linux 2.6.13) behav-
                     ior.  A core dump will not  be  produced  for  a  process
                     which  has  changed  credentials  (by calling seteuid(2),
                     setgid(2), or similar, or by executing a  set-user-ID  or
                     set-group-ID  program) or whose binary does not have read
                     permission enabled.

              1 ("debug")
                     All processes dump core when possible.   (Reasons  why  a
                     process might nevertheless not dump core are described in
                     core(5).)  The core dump is owned by the filesystem  user
                     ID  of  the  dumping  process and no security is applied.
                     This is intended for system  debugging  situations  only:
                     this  mode  is  insecure  because  it allows unprivileged
                     users to examine the memory contents of  privileged  pro-
                     cesses.

              2 ("suidsafe")
                     Any  binary  which  normally would not be dumped (see "0"
                     above) is dumped readable by root only.  This allows  the
                     user  to  remove  the  core dump file but not to read it.
                     For security reasons core dumps in  this  mode  will  not
                     overwrite  one  another  or  other  files.   This mode is
                     appropriate when administrators are attempting  to  debug
                     problems in a normal environment.

                     Additionally, since Linux 3.6, /proc/sys/kernel/core_pat-
                     tern must either be an absolute pathname or a  pipe  com-
                     mand,  as  detailed in core(5).  Warnings will be written
                     to the kernel log if core_pattern does not  follow  these
                     rules, and no core dump will be produced.

              For  details  of the effect of a process's "dumpable" setting on
              ptrace access mode checking, see ptrace(2).

       /proc/sys/fs/super-max
              This file controls the maximum number of superblocks,  and  thus
              the  maximum  number of mounted filesystems the kernel can have.
              You need increase only super-max  if  you  need  to  mount  more
              filesystems than the current value in super-max allows you to.

       /proc/sys/fs/super-nr
              This file contains the number of filesystems currently mounted.

       /proc/sys/kernel
              This  directory  contains  files  controlling  a range of kernel
              parameters, as described below.

       /proc/sys/kernel/acct
              This file contains three numbers: highwater, lowwater, and  fre-
              quency.   If BSD-style process accounting is enabled, these val-
              ues control its behavior.  If free space on filesystem where the
              log  lives goes below lowwater percent, accounting suspends.  If
              free space gets above  highwater  percent,  accounting  resumes.
              frequency  determines  how often the kernel checks the amount of
              free space (value is in seconds).  Default values are 4,  2  and
              30.   That  is,  suspend accounting if 2% or less space is free;
              resume it if 4% or more  space  is  free;  consider  information
              about amount of free space valid for 30 seconds.

       /proc/sys/kernel/auto_msgmni (Linux 2.6.27 to 3.18)
              From  Linux 2.6.27 to 3.18, this file was used to control recom-
              puting of the value in /proc/sys/kernel/msgmni upon the addition
              or  removal  of  memory  or upon IPC namespace creation/removal.
              Echoing "1" into this file enabled msgmni automatic  recomputing
              (and  triggered  a  recomputation of msgmni based on the current
              amount of available memory and number of IPC namespaces).  Echo-
              ing  "0" disabled automatic recomputing.  (Automatic recomputing
              was  also  disabled  if  a  value  was  explicitly  assigned  to
              /proc/sys/kernel/msgmni.)   The default value in auto_msgmni was
              1.

              Since Linux 3.19,  the  content  of  this  file  has  no  effect
              (because  msgmni  defaults  to near the maximum value possible),
              and reads from this file always return the value "0".

       /proc/sys/kernel/cap_last_cap (since Linux 3.2)
              See capabilities(7).

       /proc/sys/kernel/cap-bound (from Linux 2.2 to 2.6.24)
              This file holds the value of the kernel capability bounding  set
              (expressed  as  a  signed  decimal  number).   This set is ANDed
              against  the  capabilities  permitted  to   a   process   during
              execve(2).  Starting with Linux 2.6.25, the system-wide capabil-
              ity bounding set disappeared, and was replaced by  a  per-thread
              bounding set; see capabilities(7).

       /proc/sys/kernel/core_pattern
              See core(5).

       /proc/sys/kernel/core_pipe_limit
              See core(5).

       /proc/sys/kernel/core_uses_pid
              See core(5).

       /proc/sys/kernel/ctrl-alt-del
              This  file  controls  the handling of Ctrl-Alt-Del from the key-
              board.  When the value  in  this  file  is  0,  Ctrl-Alt-Del  is
              trapped  and  sent  to  the init(1) program to handle a graceful
              restart.  When the value is greater than zero, Linux's  reaction
              to  a Vulcan Nerve Pinch (tm) will be an immediate reboot, with-
              out even syncing its dirty buffers.  Note: when a program  (like
              dosemu)  has  the  keyboard  in  "raw" mode, the ctrl-alt-del is
              intercepted by the program before it ever reaches the kernel tty
              layer, and it's up to the program to decide what to do with it.

       /proc/sys/kernel/dmesg_restrict (since Linux 2.6.37)
              The value in this file determines who can see kernel syslog con-
              tents.  A value of 0 in this file imposes no  restrictions.   If
              the  value  is 1, only privileged users can read the kernel sys-
              log.  (See syslog(2) for more details.)  Since Linux  3.4,  only
              users  with the CAP_SYS_ADMIN capability may change the value in
              this file.

       /proc/sys/kernel/domainname and /proc/sys/kernel/hostname
              can be used to set the NIS/YP domainname  and  the  hostname  of
              your  box  in exactly the same way as the commands domainname(1)
              and hostname(1), that is:

                  # echo 'darkstar' > /proc/sys/kernel/hostname
                  # echo 'mydomain' > /proc/sys/kernel/domainname

              has the same effect as

                  # hostname 'darkstar'
                  # domainname 'mydomain'

              Note, however, that the classic darkstar.frop.org has the  host-
              name "darkstar" and DNS (Internet Domain Name Server) domainname
              "frop.org", not to be confused with the NIS (Network Information
              Service)  or  YP  (Yellow  Pages)  domainname.  These two domain
              names are in general different.  For a detailed  discussion  see
              the hostname(1) man page.

       /proc/sys/kernel/hotplug
              This  file  contains the path for the hotplug policy agent.  The
              default value in this file is /sbin/hotplug.

       /proc/sys/kernel/htab-reclaim (before Linux 2.4.9.2)
              (PowerPC only) If this file is set to a nonzero value, the  Pow-
              erPC  htab  (see kernel file Documentation/powerpc/ppc_htab.txt)
              is pruned each time the system hits the idle loop.

       /proc/sys/kernel/keys/*
              This directory contains various files that define parameters and
              limits   for  the  key-management  facility.   These  files  are
              described in keyrings(7).

       /proc/sys/kernel/kptr_restrict (since Linux 2.6.38)
              The value in this file determines whether kernel  addresses  are
              exposed  via  /proc files and other interfaces.  A value of 0 in
              this file imposes no restrictions.  If the value  is  1,  kernel
              pointers printed using the %pK format specifier will be replaced
              with zeros unless the user has the  CAP_SYSLOG  capability.   If
              the  value  is  2,  kernel pointers printed using the %pK format
              specifier will be replaced with zeros regardless of  the  user's
              capabilities.   The  initial  default value for this file was 1,
              but the default was changed to 0 in Linux 2.6.39.   Since  Linux
              3.4, only users with the CAP_SYS_ADMIN capability can change the
              value in this file.

       /proc/sys/kernel/l2cr
              (PowerPC only) This file contains a flag that  controls  the  L2
              cache  of  G3  processor  boards.   If 0, the cache is disabled.
              Enabled if nonzero.

       /proc/sys/kernel/modprobe
              This file contains the path for the kernel module  loader.   The
              default  value  is  /sbin/modprobe.  The file is present only if
              the kernel is built  with  the  CONFIG_MODULES  (CONFIG_KMOD  in
              Linux  2.6.26  and  earlier) option enabled.  It is described by
              the Linux kernel  source  file  Documentation/kmod.txt  (present
              only in kernel 2.4 and earlier).

       /proc/sys/kernel/modules_disabled (since Linux 2.6.31)
              A toggle value indicating if modules are allowed to be loaded in
              an otherwise modular kernel.  This toggle defaults to  off  (0),
              but  can  be  set  true  (1).  Once true, modules can be neither
              loaded nor unloaded, and the toggle cannot be set back to false.
              The  file  is  present only if the kernel is built with the CON-
              FIG_MODULES option enabled.

       /proc/sys/kernel/msgmax (since Linux 2.2)
              This file defines a system-wide  limit  specifying  the  maximum
              number  of  bytes in a single message written on a System V mes-
              sage queue.

       /proc/sys/kernel/msgmni (since Linux 2.4)
              This file defines the system-wide limit on the number of message
              queue identifiers.  See also /proc/sys/kernel/auto_msgmni.

       /proc/sys/kernel/msgmnb (since Linux 2.2)
              This file defines a system-wide parameter used to initialize the
              msg_qbytes setting for subsequently created message queues.  The
              msg_qbytes  setting  specifies  the maximum number of bytes that
              may be written to the message queue.

       /proc/sys/kernel/ngroups_max (since Linux 2.6.4)
              This is a read-only file that displays the upper  limit  on  the
              number of a process's group memberships.

       /proc/sys/kernel/ostype and /proc/sys/kernel/osrelease
              These files give substrings of /proc/version.

       /proc/sys/kernel/overflowgid and /proc/sys/kernel/overflowuid
              These  files  duplicate  the  files /proc/sys/fs/overflowgid and
              /proc/sys/fs/overflowuid.

       /proc/sys/kernel/panic
              This  file  gives  read/write  access  to  the  kernel  variable
              panic_timeout.   If  this  is  zero,  the  kernel will loop on a
              panic; if nonzero, it indicates that the kernel  should  autore-
              boot  after  this  number of seconds.  When you use the software
              watchdog device driver, the recommended setting is 60.

       /proc/sys/kernel/panic_on_oops (since Linux 2.5.68)
              This file controls the kernel's behavior when an oops or BUG  is
              encountered.   If this file contains 0, then the system tries to
              continue operation.  If it contains 1, then the system delays  a
              few  seconds  (to give klogd time to record the oops output) and
              then  panics.   If  the  /proc/sys/kernel/panic  file  is   also
              nonzero, then the machine will be rebooted.

       /proc/sys/kernel/pid_max (since Linux 2.5.34)
              This  file  specifies the value at which PIDs wrap around (i.e.,
              the value in this file is one greater  than  the  maximum  PID).
              PIDs  greater than this value are not allocated; thus, the value
              in this file also acts as a system-wide limit on the total  num-
              ber  of processes and threads.  The default value for this file,
              32768, results in the same range of PIDs as on earlier  kernels.
              On 32-bit platforms, 32768 is the maximum value for pid_max.  On
              64-bit systems, pid_max can be set  to  any  value  up  to  2^22
              (PID_MAX_LIMIT, approximately 4 million).

       /proc/sys/kernel/powersave-nap (PowerPC only)
              This file contains a flag.  If set, Linux-PPC will use the "nap"
              mode of powersaving, otherwise the "doze" mode will be used.

       /proc/sys/kernel/printk
              See syslog(2).

       /proc/sys/kernel/pty (since Linux 2.6.4)
              This directory contains two files relating to the number of UNIX
              98 pseudoterminals (see pts(4)) on the system.

       /proc/sys/kernel/pty/max
              This file defines the maximum number of pseudoterminals.

       /proc/sys/kernel/pty/nr
              This  read-only file indicates how many pseudoterminals are cur-
              rently in use.

       /proc/sys/kernel/random
              This directory contains various parameters controlling the oper-
              ation of the file /dev/random.  See random(4) for further infor-
              mation.

       /proc/sys/kernel/random/uuid (since Linux 2.4)
              Each read from this read-only file returns a randomly  generated
              128-bit UUID, as a string in the standard UUID format.

       /proc/sys/kernel/randomize_va_space (since Linux 2.6.12)
              Select  the address space layout randomization (ASLR) policy for
              the system (on architectures that support ASLR).   Three  values
              are supported for this file:

              0  Turn  ASLR  off.   This is the default for architectures that
                 don't support ASLR, and when the kernel is  booted  with  the
                 norandmaps parameter.

              1  Make the addresses of mmap(2) allocations, the stack, and the
                 VDSO page randomized.  Among other things,  this  means  that
                 shared libraries will be loaded at randomized addresses.  The
                 text segment of PIE-linked binaries will also be loaded at  a
                 randomized  address.  This value is the default if the kernel
                 was configured with CONFIG_COMPAT_BRK.

              2  (Since Linux 2.6.25) Also support heap  randomization.   This
                 value  is  the  default if the kernel was not configured with
                 CONFIG_COMPAT_BRK.

       /proc/sys/kernel/real-root-dev
              This file is documented in the Linux kernel source file Documen-
              tation/admin-guide/initrd.rst    (or    Documentation/initrd.txt
              before Linux 4.10).

       /proc/sys/kernel/reboot-cmd (Sparc only)
              This file seems to be a way to give an  argument  to  the  SPARC
              ROM/Flash  boot  loader.   Maybe  to  tell  it  what to do after
              rebooting?

       /proc/sys/kernel/rtsig-max
              (Only in kernels up to and including  2.6.7;  see  setrlimit(2))
              This  file can be used to tune the maximum number of POSIX real-
              time (queued) signals that can be outstanding in the system.

       /proc/sys/kernel/rtsig-nr
              (Only in kernels up to and including 2.6.7.)   This  file  shows
              the number of POSIX real-time signals currently queued.

       /proc/[pid]/sched_autogroup_enabled (since Linux 2.6.38)
              See sched(7).

       /proc/sys/kernel/sched_child_runs_first (since Linux 2.6.23)
              If this file contains the value zero, then, after a fork(2), the
              parent is first scheduled on the CPU.  If the  file  contains  a
              nonzero  value,  then  the  child is scheduled first on the CPU.
              (Of course, on a multiprocessor system, the parent and the child
              might both immediately be scheduled on a CPU.)

       /proc/sys/kernel/sched_rr_timeslice_ms (since Linux 3.9)
              See sched_rr_get_interval(2).

       /proc/sys/kernel/sched_rt_period_us (since Linux 2.6.25)
              See sched(7).

       /proc/sys/kernel/sched_rt_runtime_us (since Linux 2.6.25)
              See sched(7).

       /proc/sys/kernel/sem (since Linux 2.4)
              This  file  contains  4 numbers defining limits for System V IPC
              semaphores.  These fields are, in order:

              SEMMSL  The maximum semaphores per semaphore set.

              SEMMNS  A system-wide limit on the number of semaphores  in  all
                      semaphore sets.

              SEMOPM  The  maximum  number of operations that may be specified
                      in a semop(2) call.

              SEMMNI  A system-wide limit on the maximum number  of  semaphore
                      identifiers.

       /proc/sys/kernel/sg-big-buff
              This file shows the size of the generic SCSI device (sg) buffer.
              You can't tune it just yet, but you could change it  at  compile
              time  by  editing  include/scsi/sg.h  and  changing the value of
              SG_BIG_BUFF.  However, there shouldn't be any reason  to  change
              this value.

       /proc/sys/kernel/shm_rmid_forced (since Linux 3.1)
              If  this  file  is set to 1, all System V shared memory segments
              will be marked for destruction as soon as the number of attached
              processes  falls to zero; in other words, it is no longer possi-
              ble to create shared memory segments that exist independently of
              any attached process.

              The effect is as though a shmctl(2) IPC_RMID is performed on all
              existing segments as well as all segments created in the  future
              (until  this  file  is reset to 0).  Note that existing segments
              that are attached to no process will  be  immediately  destroyed
              when  this  file  is  set  to  1.  Setting this option will also
              destroy segments that were created,  but  never  attached,  upon
              termination  of  the  process  that  created  the  segment  with
              shmget(2).

              Setting this file to 1 provides a way of ensuring that all  Sys-
              tem  V  shared  memory segments are counted against the resource
              usage and resource limits (see the description of  RLIMIT_AS  in
              getrlimit(2)) of at least one process.

              Because  setting  this  file to 1 produces behavior that is non-
              standard and could also break existing applications, the default
              value  in this file is 0.  Set this file to 1 only if you have a
              good understanding of the semantics of  the  applications  using
              System V shared memory on your system.

       /proc/sys/kernel/shmall (since Linux 2.2)
              This  file contains the system-wide limit on the total number of
              pages of System V shared memory.

       /proc/sys/kernel/shmmax (since Linux 2.2)
              This file can be used to query and set the run-time limit on the
              maximum  (System  V  IPC) shared memory segment size that can be
              created.  Shared memory segments up to 1GB are now supported  in
              the kernel.  This value defaults to SHMMAX.

       /proc/sys/kernel/shmmni (since Linux 2.4)
              This  file  specifies the system-wide maximum number of System V
              shared memory segments that can be created.

       /proc/sys/kernel/sysctl_writes_strict (since Linux 3.16)
              The value in this file determines how the  file  offset  affects
              the  behavior of updating entries in files under /proc/sys.  The
              file has three possible values:

              -1  This provides legacy  handling,  with  no  printk  warnings.
                  Each  write(2)  must  fully contain the value to be written,
                  and multiple writes on the same file descriptor  will  over-
                  write the entire value, regardless of the file position.

              0   (default)  This  provides  the  same behavior as for -1, but
                  printk warnings  are  written  for  processes  that  perform
                  writes when the file offset is not 0.

              1   Respect  the file offset when writing strings into /proc/sys
                  files.  Multiple writes will append  to  the  value  buffer.
                  Anything written beyond the maximum length of the value buf-
                  fer will be ignored.  Writes to  numeric  /proc/sys  entries
                  must  always be at file offset 0 and the value must be fully
                  contained in the buffer provided to write(2).

       /proc/sys/kernel/sysrq
              This file controls the functions allowed to be  invoked  by  the
              SysRq  key.   By default, the file contains 1 meaning that every
              possible SysRq request is allowed  (in  older  kernel  versions,
              SysRq was disabled by default, and you were required to specifi-
              cally enable it at run-time, but this is not the case any more).
              Possible values in this file are:

              0    Disable sysrq completely

              1    Enable all functions of sysrq

              > 1  Bit mask of allowed sysrq functions, as follows:
                     2  Enable control of console logging level
                     4  Enable control of keyboard (SAK, unraw)
                     8  Enable debugging dumps of processes etc.
                    16  Enable sync command
                    32  Enable remount read-only
                    64  Enable signaling of processes (term, kill, oom-kill)
                   128  Allow reboot/poweroff
                   256  Allow nicing of all real-time tasks

              This  file is present only if the CONFIG_MAGIC_SYSRQ kernel con-
              figuration option is enabled.  For further details see the Linux
              kernel source file Documentation/admin-guide/sysrq.rst (or Docu-
              mentation/sysrq.txt before Linux 4.10).

       /proc/sys/kernel/version
              This file contains a string such as:

                  #5 Wed Feb 25 21:49:24 MET 1998

              The "#5" means that this is the fifth  kernel  built  from  this
              source  base  and  the  date following it indicates the time the
              kernel was built.

       /proc/sys/kernel/threads-max (since Linux 2.3.11)
              This file specifies the  system-wide  limit  on  the  number  of
              threads (tasks) that can be created on the system.

              Since Linux 4.1, the value that can be written to threads-max is
              bounded.  The minimum value that can be written is 20.  The max-
              imum  value  that  can  be  written  is  given  by  the constant
              FUTEX_TID_MASK (0x3fffffff).  If a value outside of  this  range
              is written to threads-max, the error EINVAL occurs.

              The  value  written  is checked against the available RAM pages.
              If the thread structures would occupy too much (more than 1/8th)
              of the available RAM pages, threads-max is reduced accordingly.

       /proc/sys/kernel/yama/ptrace_scope (since Linux 3.5)
              See ptrace(2).

       /proc/sys/kernel/zero-paged (PowerPC only)
              This  file  contains  a flag.  When enabled (nonzero), Linux-PPC
              will pre-zero pages in  the  idle  loop,  possibly  speeding  up
              get_free_pages.

       /proc/sys/net
              This directory contains networking stuff.  Explanations for some
              of the files under this directory can be  found  in  tcp(7)  and
              ip(7).

       /proc/sys/net/core/bpf_jit_enable
              See bpf(2).

       /proc/sys/net/core/somaxconn
              This  file  defines  a ceiling value for the backlog argument of
              listen(2); see the listen(2) manual page for details.

       /proc/sys/proc
              This directory may be empty.

       /proc/sys/sunrpc
              This directory supports Sun remote procedure  call  for  network
              filesystem (NFS).  On some systems, it is not present.

       /proc/sys/user (since Linux 4.9)
              See namespaces(7).

       /proc/sys/vm
              This directory contains files for memory management tuning, buf-
              fer and cache management.

       /proc/sys/vm/admin_reserve_kbytes (since Linux 3.10)
              This file defines the amount of free memory (in KiB) on the sys-
              tem  that  that should be reserved for users with the capability
              CAP_SYS_ADMIN.

              The default value in this file is the minimum  of  [3%  of  free
              pages,  8MiB] expressed as KiB.  The default is intended to pro-
              vide enough for the superuser to log in and kill a  process,  if
              necessary, under the default overcommit 'guess' mode (i.e., 0 in
              /proc/sys/vm/overcommit_memory).

              Systems  running  in  "overcommit  never"  mode  (i.e.,   2   in
              /proc/sys/vm/overcommit_memory)  should  increase  the  value in
              this file to account for the full virtual  memory  size  of  the
              programs  used  to  recover  (e.g., login(1) ssh(1), and top(1))
              Otherwise, the superuser may not be able to log  in  to  recover
              the  system.   For example, on x86_64 a suitable value is 131072
              (128MiB reserved).

              Changing the value in this file takes effect whenever an  appli-
              cation requests memory.

       /proc/sys/vm/compact_memory (since Linux 2.6.35)
              When  1  is  written  to this file, all zones are compacted such
              that free memory is available in contiguous blocks where  possi-
              ble.   The  effect  of  this  action  can  be  seen by examining
              /proc/buddyinfo.

              Present only if  the  kernel  was  configured  with  CONFIG_COM-
              PACTION.

       /proc/sys/vm/drop_caches (since Linux 2.6.16)
              Writing  to  this  file  causes the kernel to drop clean caches,
              dentries, and inodes from memory, causing that memory to  become
              free.  This can be useful for memory management testing and per-
              forming reproducible filesystem benchmarks.  Because writing  to
              this  file  causes  the  benefits  of caching to be lost, it can
              degrade overall system performance.

              To free pagecache, use:

                  echo 1 > /proc/sys/vm/drop_caches

              To free dentries and inodes, use:

                  echo 2 > /proc/sys/vm/drop_caches

              To free pagecache, dentries and inodes, use:

                  echo 3 > /proc/sys/vm/drop_caches

              Because writing to this file is a nondestructive  operation  and
              dirty  objects  are  not  freeable,  the user should run sync(1)
              first.

       /proc/sys/vm/legacy_va_layout (since Linux 2.6.9)
              If nonzero, this disables the new 32-bit memory-mapping  layout;
              the kernel will use the legacy (2.4) layout for all processes.

       /proc/sys/vm/memory_failure_early_kill (since Linux 2.6.32)
              Control  how  to kill processes when an uncorrected memory error
              (typically a 2-bit error in a memory module) that cannot be han-
              dled  by  the  kernel is detected in the background by hardware.
              In some cases (like the page still having a valid copy on disk),
              the kernel will handle the failure transparently without affect-
              ing any applications.  But if there is no other up-to-date  copy
              of  the data, it will kill processes to prevent any data corrup-
              tions from propagating.

              The file has one of the following values:

              1:  Kill all processes that have  the  corrupted-and-not-reload-
                  able  page  mapped  as  soon  as the corruption is detected.
                  Note that this is not supported for a few  types  of  pages,
                  such  as kernel internally allocated data or the swap cache,
                  but works for the majority of user pages.

              0:  Unmap the corrupted page  from  all  processes  and  kill  a
                  process only if it tries to access the page.

              The  kill is performed using a SIGBUS signal with si_code set to
              BUS_MCEERR_AO.  Processes can handle this if they want  to;  see
              sigaction(2) for more details.

              This  feature  is  active  only  on architectures/platforms with
              advanced machine check handling  and  depends  on  the  hardware
              capabilities.

              Applications  can override the memory_failure_early_kill setting
              individually with the prctl(2) PR_MCE_KILL operation.

              Present only if  the  kernel  was  configured  with  CONFIG_MEM-
              ORY_FAILURE.

       /proc/sys/vm/memory_failure_recovery (since Linux 2.6.32)
              Enable memory failure recovery (when supported by the platform)

              1:  Attempt recovery.

              0:  Always panic on a memory failure.

              Present  only  if  the  kernel  was  configured with CONFIG_MEM-
              ORY_FAILURE.

       /proc/sys/vm/oom_dump_tasks (since Linux 2.6.25)
              Enables a system-wide task dump (excluding kernel threads) to be
              produced  when  the  kernel  performs  an OOM-killing.  The dump
              includes  the  following  information  for  each  task  (thread,
              process): thread ID, real user ID, thread group ID (process ID),
              virtual memory size, resident set size, the CPU that the task is
              scheduled   on,   oom_adj   score   (see   the   description  of
              /proc/[pid]/oom_adj), and command  name.   This  is  helpful  to
              determine  why  the  OOM-killer  was invoked and to identify the
              rogue task that caused it.

              If this contains the value zero, this information is suppressed.
              On  very  large  systems  with thousands of tasks, it may not be
              feasible to dump the memory  state  information  for  each  one.
              Such systems should not be forced to incur a performance penalty
              in OOM situations when the information may not be desired.

              If this is set to nonzero, this information  is  shown  whenever
              the OOM-killer actually kills a memory-hogging task.

              The default value is 0.

       /proc/sys/vm/oom_kill_allocating_task (since Linux 2.6.24)
              This enables or disables killing the OOM-triggering task in out-
              of-memory situations.

              If this is set to zero, the OOM-killer  will  scan  through  the
              entire  tasklist  and select a task based on heuristics to kill.
              This normally selects a rogue memory-hogging task that frees  up
              a large amount of memory when killed.

              If  this is set to nonzero, the OOM-killer simply kills the task
              that triggered the out-of-memory condition.  This avoids a  pos-
              sibly expensive tasklist scan.

              If  /proc/sys/vm/panic_on_oom  is  nonzero,  it takes precedence
              over whatever value is  used  in  /proc/sys/vm/oom_kill_allocat-
              ing_task.

              The default value is 0.

       /proc/sys/vm/overcommit_kbytes (since Linux 3.14)
              This writable file provides an alternative to /proc/sys/vm/over-
              commit_ratio    for    controlling    the    CommitLimit    when
              /proc/sys/vm/overcommit_memory  has  the value 2.  It allows the
              amount of memory overcommitting to be specified as  an  absolute
              value  (in  kB),  rather  than  as a percentage, as is done with
              overcommit_ratio.  This allows for finer-grained control of Com-
              mitLimit on systems with extremely large memory sizes.

              Only  one  of  overcommit_kbytes or overcommit_ratio can have an
              effect: if overcommit_kbytes has a nonzero  value,  then  it  is
              used  to  calculate  CommitLimit,  otherwise overcommit_ratio is
              used.  Writing a value to either of these files causes the value
              in the other file to be set to zero.

       /proc/sys/vm/overcommit_memory
              This  file  contains  the kernel virtual memory accounting mode.
              Values are:

                     0: heuristic overcommit (this is the default)
                     1: always overcommit, never check
                     2: always check, never overcommit

              In mode 0, calls of mmap(2) with MAP_NORESERVE are not  checked,
              and  the default check is very weak, leading to the risk of get-
              ting a process "OOM-killed".

              In mode 1, the kernel pretends there is  always  enough  memory,
              until  memory  actually runs out.  One use case for this mode is
              scientific  computing  applications  that  employ  large  sparse
              arrays.   In  Linux  kernel  versions  before 2.6.0, any nonzero
              value implies mode 1.

              In mode 2 (available since Linux 2.6), the total virtual address
              space  that  can  be allocated (CommitLimit in /proc/meminfo) is
              calculated as

                  CommitLimit = (total_RAM - total_huge_TLB) *
                                overcommit_ratio / 100 + total_swap

              where:

                   *  total_RAM is the total amount of RAM on the system;

                   *  total_huge_TLB is the amount of  memory  set  aside  for
                      huge pages;

                   *  overcommit_ratio  is  the value in /proc/sys/vm/overcom-
                      mit_ratio; and

                   *  total_swap is the amount of swap space.

              For example, on a system with 16GB  of  physical  RAM,  16GB  of
              swap,  no space dedicated to huge pages, and an overcommit_ratio
              of 50, this formula yields a CommitLimit of 24GB.

              Since Linux 3.14, if the value in /proc/sys/vm/overcommit_kbytes
              is nonzero, then CommitLimit is instead calculated as:

                  CommitLimit = overcommit_kbytes + total_swap

              See  also  the description of /proc/sys/vm/admiin_reserve_kbytes
              and /proc/sys/vm/user_reserve_kbytes.

       /proc/sys/vm/overcommit_ratio (since Linux 2.6.0)
              This writable file defines a percentage by which memory  can  be
              overcommitted.   The  default  value in the file is 50.  See the
              description of /proc/sys/vm/overcommit_memory.

       /proc/sys/vm/panic_on_oom (since Linux 2.6.18)
              This enables or disables a kernel panic in an out-of-memory sit-
              uation.

              If this file is set to the value 0, the kernel's OOM-killer will
              kill some rogue process.  Usually, the  OOM-killer  is  able  to
              kill a rogue process and the system will survive.

              If  this  file  is  set to the value 1, then the kernel normally
              panics when out-of-memory happens.  However, if a process limits
              allocations  to  certain  nodes  using memory policies (mbind(2)
              MPOL_BIND) or cpusets (cpuset(7)) and those nodes  reach  memory
              exhaustion  status, one process may be killed by the OOM-killer.
              No panic occurs in this case: because other nodes' memory may be
              free,  this  means the system as a whole may not have reached an
              out-of-memory situation yet.

              If this file is set to the value 2,  the  kernel  always  panics
              when an out-of-memory condition occurs.

              The default value is 0.  1 and 2 are for failover of clustering.
              Select either according to your policy of failover.

       /proc/sys/vm/swappiness
              The value in this file controls how aggressively the kernel will
              swap memory pages.  Higher values increase aggressiveness, lower
              values decrease aggressiveness.  The default value is 60.

       /proc/sys/vm/user_reserve_kbytes (since Linux 3.10)
              Specifies an amount of memory (in KiB) to reserve for user  pro-
              cesses,  This is intended to prevent a user from starting a sin-
              gle memory hogging process, such that they cannot recover  (kill
              the  hog).   The  value  in  this  file  has an effect only when
              /proc/sys/vm/overcommit_memory is set to 2  ("overcommit  never"
              mode).   In  this  case, the system reserves an amount of memory
              that  is  the  minimum  of  [3%   of   current   process   size,
              user_reserve_kbytes].

              The  default  value  in  this file is the minimum of [3% of free
              pages, 128MiB] expressed as KiB.

              If the value in this file is set to zero, then a  user  will  be
              allowed to allocate all free memory with a single process (minus
              the amount reserved by /proc/sys/vm/admin_reserve_kbytes).   Any
              subsequent  attempts  to execute a command will result in "fork:
              Cannot allocate memory".

              Changing the value in this file takes effect whenever an  appli-
              cation requests memory.

       /proc/sysrq-trigger (since Linux 2.4.21)
              Writing  a  character to this file triggers the same SysRq func-
              tion as typing ALT-SysRq-<character>  (see  the  description  of
              /proc/sys/kernel/sysrq).  This file is normally writable only by
              root.  For further details see the Linux kernel source file Doc-
              umentation/admin-guide/sysrq.rst   (or   Documentation/sysrq.txt
              before Linux 4.10).

       /proc/sysvipc
              Subdirectory containing  the  pseudo-files  msg,  sem  and  shm.
              These  files  list the System V Interprocess Communication (IPC)
              objects (respectively: message queues,  semaphores,  and  shared
              memory)  that  currently  exist on the system, providing similar
              information to that available via  ipcs(1).   These  files  have
              headers  and  are  formatted  (one IPC object per line) for easy
              understanding.  svipc(7)  provides  further  background  on  the
              information shown by these files.

       /proc/thread-self (since Linux 3.17)
              This directory refers to the thread accessing the /proc filesys-
              tem, and is identical  to  the  /proc/self/task/[tid]  directory
              named by the process thread ID ([tid]) of the same thread.

       /proc/timer_list (since Linux 2.6.21)
              This  read-only  file  exposes  a  list of all currently pending
              (high-resolution) timers, all  clock-event  sources,  and  their
              parameters in a human-readable form.

       /proc/timer_stats (from  Linux 2.6.21 until Linux 4.10)
              This  is  a  debugging facility to make timer (ab)use in a Linux
              system visible to kernel and user-space developers.  It  can  be
              used  by  kernel  and user-space developers to verify that their
              code does not make undue use of timers.  The goal  is  to  avoid
              unnecessary wakeups, thereby optimizing power consumption.

              If  enabled in the kernel (CONFIG_TIMER_STATS), but not used, it
              has almost zero runtime overhead and a  relatively  small  data-
              structure  overhead.   Even if collection is enabled at runtime,
              overhead is low: all  the  locking  is  per-CPU  and  lookup  is
              hashed.

              The  /proc/timer_stats  file  is  used  both to control sampling
              facility and to read out the sampled information.

              The timer_stats functionality is inactive on bootup.  A sampling
              period can be started using the following command:

                  # echo 1 > /proc/timer_stats

              The following command stops a sampling period:

                  # echo 0 > /proc/timer_stats

              The statistics can be retrieved by:

                  $ cat /proc/timer_stats

              While  sampling  is enabled, each readout from /proc/timer_stats
              will see newly updated statistics.  Once sampling  is  disabled,
              the  sampled  information  is  kept until a new sample period is
              started.  This allows multiple readouts.

              Sample output from /proc/timer_stats:

    $ cat /proc/timer_stats
    Timer Stats Version: v0.3
    Sample period: 1.764 s
    Collection: active
      255,     0 swapper/3        hrtimer_start_range_ns (tick_sched_timer)
       71,     0 swapper/1        hrtimer_start_range_ns (tick_sched_timer)
       58,     0 swapper/0        hrtimer_start_range_ns (tick_sched_timer)
        4,  1694 gnome-shell      mod_delayed_work_on (delayed_work_timer_fn)
       17,     7 rcu_sched        rcu_gp_kthread (process_timeout)
    ...
        1,  4911 kworker/u16:0    mod_delayed_work_on (delayed_work_timer_fn)
       1D,  2522 kworker/0:0      queue_delayed_work_on (delayed_work_timer_fn)
    1029 total events, 583.333 events/sec

              The output columns are:

              *  a count of the number  of  events,  optionally  (since  Linux
                 2.6.23)  followed  by  the letter 'D' if this is a deferrable
                 timer;

              *  the PID of the process that initialized the timer;

              *  the name of the process that initialized the timer;

              *  the function where the timer was initialized; and

              *  (in parentheses) the callback  function  that  is  associated
                 with the timer.

              During  the Linux 4.11 development cycle, this file  was removed
              because of security concerns, as it exposes  information  across
              namespaces.   Furthermore,  it  is  possibile to obtain the same
              information via in-kernel tracing facilities such as ftrace.

       /proc/tty
              Subdirectory containing the pseudo-files and subdirectories  for
              tty drivers and line disciplines.

       /proc/uptime
              This  file  contains two numbers: the uptime of the system (sec-
              onds), and the amount of time spent in idle process (seconds).

       /proc/version
              This string identifies the kernel version that is currently run-
              ning.   It  includes  the  contents  of /proc/sys/kernel/ostype,
              /proc/sys/kernel/osrelease  and  /proc/sys/kernel/version.   For
              example:

        Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994

       /proc/vmstat (since Linux 2.6.0)
              This file displays various virtual memory statistics.  Each line
              of this file contains a single  name-value  pair,  delimited  by
              white space.  Some files are present only if the kernel was con-
              figured with suitable options.   (In  some  cases,  the  options
              required  for  particular  files have changed across kernel ver-
              sions, so they are not listed here.  Details  can  be  found  by
              consulting the kernel source code.)  The following fields may be
              present:

              nr_free_pages (since Linux 2.6.31)

              nr_alloc_batch (since Linux 3.12)

              nr_inactive_anon (since Linux 2.6.28)

              nr_active_anon (since Linux 2.6.28)

              nr_inactive_file (since Linux 2.6.28)

              nr_active_file (since Linux 2.6.28)

              nr_unevictable (since Linux 2.6.28)

              nr_mlock (since Linux 2.6.28)

              nr_anon_pages (since Linux 2.6.18)

              nr_mapped (since Linux 2.6.0)

              nr_file_pages (since Linux 2.6.18)

              nr_dirty (since Linux 2.6.0)

              nr_writeback (since Linux 2.6.0)

              nr_slab_reclaimable (since Linux 2.6.19)

              nr_slab_unreclaimable (since Linux 2.6.19)

              nr_page_table_pages (since Linux 2.6.0)

              nr_kernel_stack (since Linux 2.6.32)
                     Amount of memory allocated to kernel stacks.

              nr_unstable (since Linux 2.6.0)

              nr_bounce (since Linux 2.6.12)

              nr_vmscan_write (since Linux 2.6.19)

              nr_vmscan_immediate_reclaim (since Linux 3.2)

              nr_writeback_temp (since Linux 2.6.26)

              nr_isolated_anon (since Linux 2.6.32)

              nr_isolated_file (since Linux 2.6.32)

              nr_shmem (since Linux 2.6.32)
                     Pages used by shmem and tmpfs(5).

              nr_dirtied (since Linux 2.6.37)

              nr_written (since Linux 2.6.37)

              nr_pages_scanned (since Linux 3.17)

              numa_hit (since Linux 2.6.18)

              numa_miss (since Linux 2.6.18)

              numa_foreign (since Linux 2.6.18)

              numa_interleave (since Linux 2.6.18)

              numa_local (since Linux 2.6.18)

              numa_other (since Linux 2.6.18)

              workingset_refault (since Linux 3.15)

              workingset_activate (since Linux 3.15)

              workingset_nodereclaim (since Linux 3.15)

              nr_anon_transparent_hugepages (since Linux 2.6.38)

              nr_free_cma (since Linux 3.7)
                     Number of free CMA (Contiguous Memory Allocator) pages.

              nr_dirty_threshold (since Linux 2.6.37)

              nr_dirty_background_threshold (since Linux 2.6.37)

              pgpgin (since Linux 2.6.0)

              pgpgout (since Linux 2.6.0)

              pswpin (since Linux 2.6.0)

              pswpout (since Linux 2.6.0)

              pgalloc_dma (since Linux 2.6.5)

              pgalloc_dma32 (since Linux 2.6.16)

              pgalloc_normal (since Linux 2.6.5)

              pgalloc_high (since Linux 2.6.5)

              pgalloc_movable (since Linux 2.6.23)

              pgfree (since Linux 2.6.0)

              pgactivate (since Linux 2.6.0)

              pgdeactivate (since Linux 2.6.0)

              pgfault (since Linux 2.6.0)

              pgmajfault (since Linux 2.6.0)

              pgrefill_dma (since Linux 2.6.5)

              pgrefill_dma32 (since Linux 2.6.16)

              pgrefill_normal (since Linux 2.6.5)

              pgrefill_high (since Linux 2.6.5)

              pgrefill_movable (since Linux 2.6.23)

              pgsteal_kswapd_dma (since Linux 3.4)

              pgsteal_kswapd_dma32 (since Linux 3.4)

              pgsteal_kswapd_normal (since Linux 3.4)

              pgsteal_kswapd_high (since Linux 3.4)

              pgsteal_kswapd_movable (since Linux 3.4)

              pgsteal_direct_dma

              pgsteal_direct_dma32 (since Linux 3.4)

              pgsteal_direct_normal (since Linux 3.4)

              pgsteal_direct_high (since Linux 3.4)

              pgsteal_direct_movable (since Linux 2.6.23)

              pgscan_kswapd_dma

              pgscan_kswapd_dma32 (since Linux 2.6.16)

              pgscan_kswapd_normal (since Linux 2.6.5)

              pgscan_kswapd_high

              pgscan_kswapd_movable (since Linux 2.6.23)

              pgscan_direct_dma

              pgscan_direct_dma32 (since Linux 2.6.16)

              pgscan_direct_normal

              pgscan_direct_high

              pgscan_direct_movable (since Linux 2.6.23)

              pgscan_direct_throttle (since Linux 3.6)

              zone_reclaim_failed (since linux 2.6.31)

              pginodesteal (since linux 2.6.0)

              slabs_scanned (since linux 2.6.5)

              kswapd_inodesteal (since linux 2.6.0)

              kswapd_low_wmark_hit_quickly (since 2.6.33)

              kswapd_high_wmark_hit_quickly (since 2.6.33)

              pageoutrun (since Linux 2.6.0)

              allocstall (since Linux 2.6.0)

              pgrotated (since Linux 2.6.0)

              drop_pagecache (since Linux 3.15)

              drop_slab (since Linux 3.15)

              numa_pte_updates (since Linux 3.8)

              numa_huge_pte_updates (since Linux 3.13)

              numa_hint_faults (since Linux 3.8)

              numa_hint_faults_local (since Linux 3.8)

              numa_pages_migrated (since Linux 3.8)

              pgmigrate_success (since Linux 3.8)

              pgmigrate_fail (since Linux 3.8)

              compact_migrate_scanned (since Linux 3.8)

              compact_free_scanned (since Linux 3.8)

              compact_isolated (since Linux 3.8)

              compact_stall (since Linux 2.6.35)
                     See  the  kernel   source   file   Documentation/vm/tran-
                     shuge.txt.

              compact_fail (since Linux 2.6.35)
                     See   the   kernel   source  file  Documentation/vm/tran-
                     shuge.txt.

              compact_success (since Linux 2.6.35)
                     See  the  kernel   source   file   Documentation/vm/tran-
                     shuge.txt.

              htlb_buddy_alloc_success (since Linux 2.6.26)

              htlb_buddy_alloc_fail (since Linux 2.6.26)

              unevictable_pgs_culled (since Linux 2.6.28)

              unevictable_pgs_scanned (since Linux 2.6.28)

              unevictable_pgs_rescued (since Linux 2.6.28)

              unevictable_pgs_mlocked (since Linux 2.6.28)

              unevictable_pgs_munlocked (since Linux 2.6.28)

              unevictable_pgs_cleared (since Linux 2.6.28)

              unevictable_pgs_stranded (since Linux 2.6.28)

              thp_fault_alloc (since Linux 2.6.39)
                     See   the   kernel   source  file  Documentation/vm/tran-
                     shuge.txt.

              thp_fault_fallback (since Linux 2.6.39)
                     See  the  kernel   source   file   Documentation/vm/tran-
                     shuge.txt.

              thp_collapse_alloc (since Linux 2.6.39)
                     See   the   kernel   source  file  Documentation/vm/tran-
                     shuge.txt.

              thp_collapse_alloc_failed (since Linux 2.6.39)
                     See  the  kernel   source   file   Documentation/vm/tran-
                     shuge.txt.

              thp_split (since Linux 2.6.39)
                     See   the   kernel   source  file  Documentation/vm/tran-
                     shuge.txt.

              thp_zero_page_alloc (since Linux 3.8)
                     See  the  kernel   source   file   Documentation/vm/tran-
                     shuge.txt.

              thp_zero_page_alloc_failed (since Linux 3.8)
                     See   the   kernel   source  file  Documentation/vm/tran-
                     shuge.txt.

              balloon_inflate (since Linux 3.18)

              balloon_deflate (since Linux 3.18)

              balloon_migrate (since Linux 3.18)

              nr_tlb_remote_flush (since Linux 3.12)

              nr_tlb_remote_flush_received (since Linux 3.12)

              nr_tlb_local_flush_all (since Linux 3.12)

              nr_tlb_local_flush_one (since Linux 3.12)

              vmacache_find_calls (since Linux 3.16)

              vmacache_find_hits (since Linux 3.16)

              vmacache_full_flushes (since Linux 3.19)

       /proc/zoneinfo (since Linux 2.6.13)
              This file display information about memory zones.  This is  use-
              ful for analyzing virtual memory behavior.

NOTES
       Many strings (i.e., the environment and command line) are in the inter-
       nal format, with subfields terminated by null bytes ('\0'), so you  may
       find  that  things are more readable if you use od -c or tr "\000" "\n"
       to read them.  Alternatively, echo `cat <file>` works well.

       This manual page is incomplete, possibly inaccurate, and is the kind of
       thing that needs to be updated very often.

SEE ALSO
       cat(1),  dmesg(1),  find(1), free(1), init(1), ps(1), tr(1), uptime(1),
       chroot(2),  mmap(2),  readlink(2),  syslog(2),  slabinfo(5),  sysfs(5),
       hier(7),   namespaces(7),   time(7),  arp(8),  hdparm(8),  ifconfig(8),
       lsmod(8),  lspci(8),  mount(8),  netstat(8),   procinfo(8),   route(8),
       sysctl(8)

       The Linux kernel source files: Documentation/filesystems/proc.txt Docu-
       mentation/sysctl/fs.txt,  Documentation/sysctl/kernel.txt,   Documenta-
       tion/sysctl/net.txt, and Documentation/sysctl/vm.txt.

COLOPHON
       This  page  is  part of release 4.13 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.

Linux                             2017-09-15                           PROC(5)

Man(1) output converted with man2html
list of all man pages