--- name: "tmpfs" section: "5" platform: "linux" package: "man-pages" version: "6.19-1" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/tmpfs" --- # tmpfs(5) a virtual memory filesystem ## NAME tmpfs - a virtual memory filesystem ## DESCRIPTION The **tmpfs** 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 **tmpfs** via a command such as the following: ``` $ sudo mount -t tmpfs -o size=10M tmpfs /mnt/mytmpfs ``` A **tmpfs** 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 filesystem. - • 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). ### Mount options The **tmpfs** filesystem supports the following mount options: - **size**=*bytes* Specify an upper limit on the size of the filesystem. The size is given in bytes, and rounded up to entire pages. The limit is removed if the size is **0**. - The size may have a **k**, **m**, or **g** suffix for Ki, Mi, Gi (binary kilo (kibi), binary mega (mebi), and binary giga (gibi)). - 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%*. - **nr\_blocks**=*blocks* The same as **size**, but in blocks of **PAGE\_CACHE\_SIZE**. - Blocks may be specified with **k**, **m**, or **g** suffixes like **size**, but not a % suffix. - **nr\_inodes**=*inodes* 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. The limit is removed if the number is **0**. - Inodes may be specified with **k**, **m**, or **g** suffixes like **size**, but not a % suffix. - **noswap**(since Linux 6.4) Disables swap. Remounts must respect the original settings. By default swap is enabled. - **mode**=*mode* 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\_HUGEPAGE** is enabled). - The *huge\_option* value is one of the following: - **never** Do not allocate huge pages. This is the default. - **always** Attempt to allocate huge pages every time a new page is needed. - **within\_size** Only allocate huge page if it will be fully within *i\_size*. Also respect **fadvise**(2) and [**madvise**(2)](/madvise/2.md) hints - **advise** Only allocate huge pages if requested with **fadvise**(2) or [**madvise**(2)](/madvise/2.md). - **deny** For use in emergencies, to force the huge option off from all mounts. - **force** Force the huge option on for all mounts; useful for testing. - **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: - **default** Use the process allocation policy (see [**set\_mempolicy**(2)](/set_mempolicy/2.md)). - **prefer**:*node* Preferably allocate memory from the given *node*. - **bind**:*nodelist* Allocate memory only from nodes in *nodelist*. - **interleave** Allocate from each node in turn. - **interleave**:*nodelist* Allocate from each node of *in* turn. - **local** 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*. ## VERSIONS The **tmpfs** facility was added in Linux 2.4, as a successor to the older **ramfs** facility, which did not provide limit checking or allow for the use of swap space. ## NOTES In order for user-space tools and applications to create **tmpfs** filesystems, the kernel must be configured with the **CONFIG\_TMPFS** option. The **tmpfs** filesystem supports extended attributes (see [**xattr**(7)](/xattr/7.md)), but *user* extended attributes are not permitted. An internal shared memory filesystem is used for System V shared memory ([**shmget**(2)](/shmget/2.md)) and shared anonymous mappings ([**mmap**(2)](/mmap/2.md) with the **MAP\_SHARED** and **MAP\_ANONYMOUS** flags). This filesystem is available regardless of whether the kernel was configured with the **CONFIG\_TMPFS** option. A **tmpfs** filesystem mounted at */dev/shm* is used for the implementation of POSIX shared memory ([**shm\_overview**(7)](/shm_overview/7.md)) and POSIX semaphores ([**sem\_overview**(7)](/sem_overview/7.md)). The amount of memory consumed by all **tmpfs** filesystems is shown in the *Shmem* field of */proc/meminfo* and in the *shared* field displayed by [**free**(1)](/free/1.md). The **tmpfs** facility was formerly called **shmfs**. ## SEE ALSO [**df**(1)](/df/1.md), [**du**(1)](/du/1.md), [**memfd\_create**(2)](/memfd_create/2.md), [**mmap**(2)](/mmap/2.md), [**set\_mempolicy**(2)](/set_mempolicy/2.md), [**shm\_open**(3)](/shm_open/3.md), [**mount**(8)](/mount/8.md) The kernel source files *Documentation/filesystems/tmpfs.rst* and *Documentation/admin-guide/mm/transhuge.rst*.