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TMPFS(5)		  FreeBSD File Formats Manual		      TMPFS(5)

     tmpfs -- in-memory	file system

     To	compile	this driver into the kernel, place the following line in your
     kernel configuration file:

	   options TMPFS

     Alternatively, to load the	driver as a module at boot time, place the
     following line in loader.conf(5):


     The tmpfs driver implements an in-memory, or tmpfs	file system.  The
     filesystem	stores both file metadata and data in main memory.  This al-
     lows very fast and	low latency accesses to	the data.  The data is
     volatile.	An umount or system reboot invalidates it.  These properties
     make the filesystem's mounts suitable for fast scratch storage, like

     If	the system becomes low on memory and swap is configured	(see swapon(8)
     ),	the system can transfer	file data to swap space, freeing memory	for
     other needs.  Metadata, including the directory content, is never swapped
     out by the	current	implementation.	 Keep this in mind when	planning the
     mount limits, especially when expecting to	place many small files on a
     tmpfs mount.

     When mmap(2) is used on a file from a tmpfs mount,	the swap VM object
     managing the file pages is	used to	implement mapping and avoid double-
     copying of	the file data.	This quirk causes process inspection tools,
     like procstat(1), to report anonymous memory mappings instead of file

     The following options are available when mounting tmpfs file systems:

     gid		Specifies the group ID of the root inode of the	file
			system.	 Defaults to the mount point's GID.

     uid		Specifies the user ID of the root inode	of the file
			system.	 Defaults to the mount point's UID.

     mode		Specifies the mode (in octal notation) of the root in-
			ode of the file	system.	 Defaults to the mount point's

     nonc		Do not use namecache to	resolve	names to files for the
			created	mount.	This saves memory, but currently might
			impair scalability for highly used mounts on large ma-

     inodes		Specifies the maximum number of	nodes available	to the
			file system.  If not specified,	the file system
			chooses	a reasonable maximum based on the file system
			size, which can	be limited with	the size option.

     size		Specifies the total file system	size in	bytes, unless
			suffixed with one of k,	m, g, t, or p, which denote
			byte, kilobyte,	megabyte, gigabyte, terabyte and
			petabyte respectively.	If zero	(the default) or a
			value larger than SIZE_MAX - PAGE_SIZE is given, the
			available amount of memory (including main memory and
			swap space) will be used.

     maxfilesize	Specifies the maximum file size	in bytes.  Defaults to
			the maximum possible value.

     To	mount a	tmpfs memory file system:

	   mount -t tmpfs tmpfs	/tmp

     procstat(1), mmap(2), nmount(2), unmount(2), fstab(5), mdmfs(8),
     mount(8), swapinfo(8), swapon(8)

     The tmpfs driver first appeared in	FreeBSD	7.0.

     The tmpfs kernel implementation was written by Julio M. Merino Vidal
     <> as a Google Summer of Code project.

     Rohit Jalan and others ported it from NetBSD to FreeBSD.

     This manual page was written by Xin LI <>.

FreeBSD	13.0		       September 8, 2017		  FreeBSD 13.0


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