tmpfs(5)

tmpfs(5) Debian Administrator's Manual tmpfs(5)

NAME
tmpfs - variables that configure tmpfs filesystems mounted during boot

DESCRIPTION
The /etc/default/tmpfs file contains variable settings in POSIX format:

VAR=VAL

Only one assignment is allowed per line. Comments (starting with '#')
are also allowed.

This file is for the configuration of tmpfs filesystems mounted in
early boot, before filesystems from /etc/fstab are mounted. This cur-
rently includes the filesystems /run, /run/lock, /run/shm and /tmp.
/run is required to be a tmpfs on systems supporting tmpfs mounts.
/run/lock and /run/shm may be separate tmpfs mounts, useful for enforc-
ing separate size limits. /tmp is not required to be a tmpfs, and is
not mounted as a tmpfs by default.

/run Previously configured using RAMRUN in /etc/default/rcS, /run is
now always mounted as a ram file system (tmpfs). The size of
the tmpfs can be controlled using TMPFS_SIZE and RUN_SIZE. If
desired, the defaults may also be overridden with an entry in in
/etc/fstab, for example:

tmpfs /run tmpfs nodev,nosuid,size=10%,mode=755 0 0

The contents of /run will always be lost on system reboot, and
it it is no longer explicitly cleaned at boot. Packages can not
expect directories in /run to exist after boot. Packages ex-
pecting this are buggy and need to be fixed. Note that /run was
previously /var/run, and a compatibility symlink or bind mount
will be created to allow the old path to continue to function.

/run/lock
Previously configured using RAMLOCK in /etc/default/rcS. Con-
figured using RAMLOCK, TMPFS_SIZE and LOCK_SIZE. If desired,
the defaults may also be overridden with an entry in in
/etc/fstab, for example:

tmpfs /run/lock tmpfs nodev,noexec,nosuid,size=52428800,mode=1777 0 0

Note that irrespective of these settings, /run/lock will be lo-
cated on a tmpfs, either one mounted on /run/lock (if RAM-
LOCK=yes) or one mounted on /run (if RAMLOCK=no), and as a re-
sult the contents of /var/lock will always be lost on system re-
boot, and it it is no longer explicitly cleaned at boot. Pack-
ages can not expect directories in /var/lock to exist after
boot. Packages expecting this are buggy and need to be fixed.
Note that /run/lock was previously /var/lock, and a compatibil-
ity symlink or bind mount will be created to allow the old path
to continue to function.

/run/shm
Previously configured using RAMSHM in /etc/default/rcS. Note
that the setting in /etc/default/rcS, if present, will still be
used, but the setting in /etc/default/tmpfs will take precedence
if enabled. Configured using RAMSHM, TMPFS_SIZE and SHM_SIZE.
If desired, the defaults may also be overridden with an entry in
in /etc/fstab, for example:

tmpfs /run/shm tmpfs nosuid,nodev,size=40%,mode=1777 0 0

Packages can not expect directories in /run/shm to exist after
boot. Note that /run/shm was previously /dev/shm, and a compat-
ibility symlink or bind mount will be created to allow the old
path to continue to function. If an fstab entry for /dev/shm
exists instead of /run/shm, then /dev/shm will continue to be
used; note that this is only needed for users of newer versions
of the Oracle database, which contain a buggy check for
/dev/shm.

/tmp Previously configured using RAMTMP in /etc/default/rcS. Note
that the setting in /etc/default/rcS, if present, will still be
used, but the setting in /etc/default/tmpfs will take precedence
if enabled. Configured using RAMTMP, TMPFS_SIZE and TMP_SIZE.
If desired, the defaults may also be overridden with an entry in
in /etc/fstab, for example:

tmpfs /tmp tmpfs nodev,nosuid,size=20%,mode=1777 0 0

Packages can not expect directories in /tmp to exist after boot.

NOTE: This file is ignored when systemd is used as init system.

OPTIONS
The following variables can be set.

Enabling or disabling tmpfs mounts
The following options enable specific mounts (with the exception of
/run) to be enabled or disabled. Note that the addition of an entry to
/etc/fstab for any of the following will enable the mount uncondition-
ally, overriding the setting here.

RAMLOCK
Mount /run/lock as a tmpfs (separately from /run). Defaults to
yes; set to no to disable (/run/lock will then be part of the
/run tmpfs, if available).

RAMSHM Mount /run/shm as a tmpfs (separately from /run). Defaults to
yes; set to no to disable (/run/shm will then be part of the
/run tmpfs, if available).

RAMTMP Mount /tmp as a tmpfs. Defaults to no; set to yes to enable
(/tmp will be part of the root filesystem if disabled). /tmp
may also be configured to be a separate mount in /etc/fstab,
which will override the RAMTMP setting.

Configuring size limits for tmpfs mounts
The following options configure size limits for tmpfs mounts. Note
that the addition of an entry to /etc/fstab will override any of the
limits specified here.

The following _SIZE variables are the maximum size (in bytes) that
tmpfs filesystems can use. The size will be rounded down to a multiple
of the page size, 4096 bytes. If no size is set, TMPFS_SIZE will be
used as the default.

More complex mount options may be used by the creation of a suitable
entry in /etc/fstab. For example:

tmpfs /run tmpfs size=10% 0 0

is equivalent to

RUN_SIZE=10%

and will override the RUN_SIZE setting. This will allow additional op-
tions such as nr_blocks and nr_inodes to be used, and also adjustment
of the mode, nodev, nosuid, noexec options should any change from the
defaults be necessary.

TMPFS_SIZE
Maximum size for all tmpfs filesystems if no specific size is
provided. The default is 20%VM (20% of virtual memory, includ-
ing swap space). If no value is provided here, the kernel de-
fault (50% RAM) will be used. Note that the "%VM" suffix may be
used in this and all the _SIZE settings below, but may not be
used in /etc/fstab (the absolute size is calculated by the init
scripts).

RUN_SIZE
Maximum size of /run (was previously /var/run). The default is
10% core memory; the size required varies widely depending upon
the demands of the software being run; this heuristic scales
/run usage on system size. Samba in particular has been seen to
use at least 50MiB in a large heavily used server. Typical us-
age is hundreds of KiB, maximum is tens of MiB.

LOCK_SIZE
Maximum size of /run/lock (was previously /var/lock). Defaults
to 5242880 (5 MiB). Typical usage: tens of KiB; maximum hun-
dreds of KiB. The default of 5 MiB should ensure the limit is
never reached.

SHM_SIZE
Maximum size of /run/shm (was previously /dev/shm). No default
size; the size required varies widely depending upon the demands
of the software being run.

TMP_SIZE
Maximum size of /tmp. No default size.

Emergency overflow /tmp
If the amount of free space on the root filesystem falls below a cer-
tain size, a tmpfs will be mounted on /tmp (irrespective of the RAMTMP
setting, which this overrides). This is to permit logins when there
would otherwise be too little free space for this to be possible.

TMP_OVERFLOW_LIMIT
Mount a tmpfs on /tmp if the amount of free space on the root
filesystem is below the specified limit at boot time (default
1024 KiB).

AUTHOR
Roger Leigh <rleigh@debian.org>