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 currently 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 enforcing 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 expecting 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.
Configured 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 located on
a tmpfs, either one mounted on /run/lock (if RAMLOCK=yes) or one
mounted on /run (if RAMLOCK=no), and as a result the contents of
/var/lock will always be lost on system reboot, and it it is no longer
explicitly cleaned at boot. Packages 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
compatibility 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 compatibility
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.
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 unconditionally, 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 options 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,
including swap space). If no value is provided here, the kernel
default (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 usage 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 hundreds 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 certain 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).