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 enforcing separate size limits.	/tmp is not required to be a tmpfs, but is
       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 previ-
	      ously /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 compatibil-
	      ity 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).

AUTHOR

       Roger Leigh <rleigh@debian.org>

SEE ALSO

       mount(8), rcS(5).

								    18 Feb 2012 							  tmpfs(5)