How to create a tmpfs mount in Linux

A tmpfs mount gives a Linux system a fast temporary workspace whose files disappear when the mount is removed or the machine reboots. It fits build caches, short-lived runtime data, and scratch directories that need a size limit instead of a real disk filesystem.

The mount command creates the filesystem when it attaches the tmpfs type to a directory. The source name is usually tmpfs, while options such as size=, mode=, nodev, and nosuid control the space cap, root directory permissions, and security boundary for that mount.

A tmpfs uses virtual memory and can use swap unless swap is disabled for that mount and kernel support is available. Set a realistic size= value before allowing users or applications to write there, because a full tmpfs returns space errors to writers and an oversized shared tmpfs can pressure memory on the host.

1. Create the mount point directory.

   $ sudo mkdir -p /mnt/ram-cache

2. Mount a sized tmpfs at the directory.

   $ sudo mount -t tmpfs -o size=256M,mode=1777,nodev,nosuid tmpfs /mnt/ram-cache

   size=256M caps this tmpfs at 256 MiB. mode=1777 gives temporary-directory permissions with the sticky bit, while nodev and nosuid reduce device-file and setuid risk.

3. Confirm the active mount options.

   $ findmnt --mountpoint /mnt/ram-cache --output TARGET,SOURCE,FSTYPE,OPTIONS
   TARGET         SOURCE FSTYPE OPTIONS
   /mnt/ram-cache tmpfs  tmpfs  rw,nosuid,nodev,relatime,size=262144k

4. Check the visible capacity.

   $ df -hT /mnt/ram-cache
   Filesystem     Type   Size  Used Avail Use% Mounted on
   tmpfs          tmpfs  256M     0  256M   0% /mnt/ram-cache

   df shows the tmpfs size limit, not preallocated RAM. The filesystem consumes memory and swap as files are written.

5. Write a test file into the tmpfs.

   $ printf 'tmpfs test\n' | tee /mnt/ram-cache/check.txt
   tmpfs test

6. Read the test file from the tmpfs.

   $ cat /mnt/ram-cache/check.txt
   tmpfs test

7. Check tmpfs usage after the write.

   $ df -hT /mnt/ram-cache
   Filesystem     Type   Size  Used Avail Use% Mounted on
   tmpfs          tmpfs  256M  4.0K  256M   1% /mnt/ram-cache

8. Unmount the tmpfs when the temporary workspace is no longer needed.

   $ sudo umount /mnt/ram-cache

   Unmounting a tmpfs discards files that only exist inside that mount. Copy needed data to persistent storage before running umount.

   Related: How to unmount a disk in Linux

9. Confirm the directory is no longer a mount point.

   $ mountpoint /mnt/ram-cache
   /mnt/ram-cache is not a mountpoint

10. Confirm the tmpfs-only test file is gone.

    $ cat /mnt/ram-cache/check.txt
    cat: /mnt/ram-cache/check.txt: No such file or directory

11. Remove the empty mount point if it was only for this temporary workspace.

    $ sudo rmdir /mnt/ram-cache