tmpfs - a virtual memory filesystem
facility allows the creation of filesystems whose contents
reside in virtual memory. Since the files on such filesystems typically reside
in RAM, file access is extremely fast.
The filesystem is automatically created when mounting a filesystem with the type
via a command such as the following:
$ sudo mount -t tmpfs -o size=10M tmpfs /mnt/mytmpfs
filesystem has the following properties:
- The filesystem can employ swap space when physical memory
pressure demands it.
- The filesystem consumes only as much physical memory and
swap space as is required to store the current contents of the
- During a remount operation
(mount -o remount), the filesystem size can be
changed (without losing the existing contents of the filesystem).
If a tmpfs
filesystem is unmounted, its contents are discarded (lost).
filesystem supports the following mount options:
- Specify an upper limit on the size of the filesystem. The
size is given in bytes, and rounded up to entire pages.
- The size may have a k, m, or g suffix
for Ki, Mi, Gi (binary kilo (kibi), binary mega (mebi) and binary giga
- The size may also have a % suffix to limit this instance to
a percentage of physical RAM.
- The default, when neither size nor nr_blocks
is specified, is size=50%.
- The same as size, but in blocks of
- Blocks may be specified with k, m, or
g suffixes like size, but not a % suffix.
- The maximum number of inodes for this instance. The default
is half of the number of your physical RAM pages, or (on a machine with
highmem) the number of lowmem RAM pages, whichever is smaller.
- Inodes may be specified with k, m, or
g suffixes like size, but not a % suffix.
- Set initial permissions of the root directory.
- gid=gid (since Linux 2.5.7)
- Set the initial group ID of the root directory.
- uid=uid (since Linux 2.5.7)
- Set the initial user ID of the root directory.
- huge=huge_option (since Linux 4.7.0)
- Set the huge table memory allocation policy for all files
in this instance (if CONFIG_TRANSPARENT_HUGE_PAGECACHE is
- The huge_option value is one of the following:
- Do not allocate huge pages. This is the default.
- Attempt to allocate huge pages every time a new page is
- Only allocate huge page if it will be fully within
i_size. Also respect fadvise(2)/madvise(2) hints
- Only allocate huge pages if requested with
- For use in emergencies, to force the huge option off from
- Force the huge option on for all mounts; useful for
- mpol=mpol_option (since Linux 2.6.15)
- Set the NUMA memory allocation policy for all files in this
instance (if CONFIG_NUMA is enabled).
- The mpol_option value is one of the following:
- Use the process allocation policy (see
- Preferably allocate memory from the given node.
- Allocate memory only from nodes in nodelist.
- Allocate from each node in turn.
- Allocate from each node of in turn.
- Preferably allocate memory from the local node.
- In the above, nodelist is a comma-separated list of
decimal numbers and ranges that specify NUMA nodes. A range is a pair of
hyphen-separated decimal numbers, the smallest and largest node numbers in
the range. For example, mpol=bind:0-3,5,7,9-15.
facility was added in Linux 2.4, as a successor to the older
facility, which did not provide limit checking or allow for the
use of swap space.
In order for user-space tools and applications to create tmpfs
filesystems, the kernel must be configured with the CONFIG_TMPFS
filesystem supports extended attributes (see xattr(7)
extended attributes are not permitted.
An internal shared memory filesystem is used for System V shared memory
) and shared anonymous mappings (mmap(2)
flags). This filesystem is
available regardless of whether the kernel was configured with the
filesystem mounted at /dev/shm
is used for the
implementation of POSIX shared memory (shm_overview(7)
) and POSIX
The amount of memory consumed by all tmpfs
filesystems is shown in the
field of /proc/meminfo
and in the shared
displayed by free(1)
facility was formerly called shmfs
The kernel source files Documentation/filesystems/tmpfs.txt
This page is part of release 4.16 of the Linux man-pages
description of the project, information about reporting bugs, and the latest
version of this page, can be found at