chattr(1)



CHATTR(1)                   General Commands Manual                  CHATTR(1)

NAME
       chattr - change file attributes on a Linux file system

SYNOPSIS
       chattr [ -RVf ] [ -v version ] [ -p project ] [ mode ] files...

DESCRIPTION
       chattr changes the file attributes on a Linux file system.

       The format of a symbolic mode is +-=[aAcCdDeijsStTu].

       The  operator  '+'  causes  the  selected attributes to be added to the
       existing attributes of the files; '-' causes them to  be  removed;  and
       '=' causes them to be the only attributes that the files have.

       The  letters  'aAcCdDeijsStTu' select the new attributes for the files:
       append only (a), no atime updates (A), compressed (c), no copy on write
       (C), no dump (d), synchronous directory updates (D), extent format (e),
       immutable (i), data journalling  (j),  project  hierarchy  (P),  secure
       deletion  (s),  synchronous  updates  (S),  no tail-merging (t), top of
       directory hierarchy (T), and undeletable (u).

       The following attributes are read-only, and may be listed by  lsattr(1)
       but  not  modified  by  chattr:  compression  error (E), huge file (h),
       indexed directory (I), inline data (N), compression raw access (X), and
       compressed dirty file (Z).

       Not  all  flags  are supported or utilized by all filesystems; refer to
       filesystem-specific man pages such as btrfs(5), ext4(5), and xfs(5) for
       more filesystem-specific details.

OPTIONS
       -R     Recursively change attributes of directories and their contents.

       -V     Be verbose with chattr's output and print the program version.

       -f     Suppress most error messages.

       -v version
              Set the file's version/generation number.

       -p project
              Set the file's project number.

ATTRIBUTES
       A  file  with the 'a' attribute set can only be open in append mode for
       writing.   Only   the   superuser   or   a   process   possessing   the
       CAP_LINUX_IMMUTABLE capability can set or clear this attribute.

       When a file with the 'A' attribute set is accessed, its atime record is
       not modified.  This avoids a certain amount of disk I/O for laptop sys-
       tems.

       A  file  with  the 'c' attribute set is automatically compressed on the
       disk by the kernel.  A read from this file returns  uncompressed  data.
       A  write  to this file compresses data before storing them on the disk.
       Note: please make sure to read the bugs and limitations section at  the
       end of this document.

       A  file with the 'C' attribute set will not be subject to copy-on-write
       updates.  This flag is only supported on  file  systems  which  perform
       copy-on-write.   (Note: For btrfs, the 'C' flag should be set on new or
       empty files.  If it is set on a file which already has data blocks,  it
       is undefined when the blocks assigned to the file will be fully stable.
       If the 'C' flag is set on a directory, it will have no  effect  on  the
       directory, but new files created in that directory will have the No_COW
       attribute set.)

       A file with the 'd' attribute set is not candidate for backup when  the
       dump(8) program is run.

       When  a  directory  with the 'D' attribute set is modified, the changes
       are written synchronously on  the  disk;  this  is  equivalent  to  the
       'dirsync' mount option applied to a subset of the files.

       The  'e' attribute indicates that the file is using extents for mapping
       the blocks on disk.  It may not be removed using chattr(1).

       The 'E' attribute is used by the  experimental  encryption  patches  to
       indicate  that the file has been encrypted.  It may not be set or reset
       using chattr(1), although it can be displayed by lsattr(1).

       The 'h' attribute indicates the file is storing its blocks in units  of
       the filesystem blocksize instead of in units of sectors, and means that
       the file is (or at one time was) larger than 2TB.  It may not be set or
       reset using chattr(1), although it can be displayed by lsattr(1).

       A  file with the 'i' attribute cannot be modified: it cannot be deleted
       or renamed, no link can be created to this file  and  no  data  can  be
       written  to  the  file.  Only the superuser or a process possessing the
       CAP_LINUX_IMMUTABLE capability can set or clear this attribute.

       The 'I' attribute is used by the htree code to indicate that  a  direc-
       tory  is  being indexed using hashed trees.  It may not be set or reset
       using chattr(1), although it can be displayed by lsattr(1).

       A file with the 'j' attribute has all of its data written to  the  ext3
       or  ext4  journal  before  being  written  to  the  file itself, if the
       filesystem is  mounted  with  the  "data=ordered"  or  "data=writeback"
       options.  When the filesystem is mounted with the "data=journal" option
       all file data is already journalled and this attribute has  no  effect.
       Only  the  superuser or a process possessing the CAP_SYS_RESOURCE capa-
       bility can set or clear this attribute.

       A file with the 'N' attribute set indicates  that  the  file  has  data
       stored  inline,  within  the  inode  itself. It may not be set or reset
       using chattr(1), although it can be displayed by lsattr(1).

       A directory with the 'P' attribute  set  will  enforce  a  hierarchical
       structure  for  project id's.  This means that files and directory cre-
       ated in the directory will inhert the  project  id  of  the  directory,
       rename  operations are constrained so when a file or directory is moved
       into another directory, that the project id's much match.  In addition,
       a  hard  link  to  file can only be created when the project id for the
       file and the destination directory match.

       When a file with the 's' attribute  set  is  deleted,  its  blocks  are
       zeroed  and  written  back to the disk.  Note: please make sure to read
       the bugs and limitations section at the end of this document.

       When a file with the 'S' attribute set is  modified,  the  changes  are
       written  synchronously  on  the  disk; this is equivalent to the 'sync'
       mount option applied to a subset of the files.

       A file with the 't' attribute will not have a partial block fragment at
       the  end  of  the  file  merged with other files (for those filesystems
       which support tail-merging).  This is necessary for  applications  such
       as  LILO which read the filesystem directly, and which don't understand
       tail-merged files.  Note: As of this writing, the ext2 or ext3 filesys-
       tems  do  not  (yet, except in very experimental patches) support tail-
       merging.

       A directory with the 'T' attribute will be deemed  to  be  the  top  of
       directory  hierarchies  for  the purposes of the Orlov block allocator.
       This is a hint to the block allocator used by ext3 and  ext4  that  the
       subdirectories under this directory are not related, and thus should be
       spread apart for allocation purposes.   For example it is a  very  good
       idea  to  set  the  'T'  attribute  on  the  /home  directory,  so that
       /home/john and /home/mary are placed into separate block  groups.   For
       directories  where this attribute is not set, the Orlov block allocator
       will try to group subdirectories closer together where possible.

       When a file with the 'u' attribute set is  deleted,  its  contents  are
       saved.   This  allows the user to ask for its undeletion.  Note: please
       make sure to read the bugs and limitations section at the end  of  this
       document.

       The  'X'  attribute  is used by the experimental compression patches to
       indicate that the raw contents of a compressed  file  can  be  accessed
       directly.   It  currently  may  not  be  set  or reset using chattr(1),
       although it can be displayed by lsattr(1).

       The 'Z' attribute is used by the experimental  compression  patches  to
       indicate  a compressed file is dirty.  It may not be set or reset using
       chattr(1), although it can be displayed by lsattr(1).

AUTHOR
       chattr was written by Remy Card <Remy.Card@linux.org>.  It is currently
       being maintained by Theodore Ts'o <tytso@alum.mit.edu>.

BUGS AND LIMITATIONS
       The  'c',  's',   and 'u' attributes are not honored by the ext2, ext3,
       and ext4 filesystems as implemented in the current mainline Linux  ker-
       nels.

       The  'j'  option is only useful if the filesystem is mounted as ext3 or
       ext4.

       The 'D' option is only useful on Linux kernel 2.5.19 and later.

AVAILABILITY
       chattr  is  part  of  the  e2fsprogs  package  and  is  available  from
       http://e2fsprogs.sourceforge.net.

SEE ALSO
       lsattr(1), btrfs(5), ext4(5), xfs(5).

E2fsprogs version 1.43.6          August 2017                        CHATTR(1)

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