Managing filesystem types

The memfs filesystem type

The memfs filesystem type is a high-performance, volatile memory filesystem type. The nature of this filesystem type is such that users are able to create directories and files, but, because the filesystem is only in memory, when it is unmounted, the directories and files go away. A a result, there is no filesystem for a system administrator to administer.

When mounting memfs, you can use the -o option to specify file-system-specific options. These file-system-specific options are:

swapmax: swapmax sets the maximum amount of memory allowed in bytes.
rootmode: rootmode specifies the mode of the root directory of mounted memfs. rootmode allows system administrators to set a sticky bit for /tmp and /var/tmp.

NOTE: Mounting an memfs filesystem creates an instantiation of the filesystem. Therefore, there is no corresponding mkfs command required for the memfs filesystem type. Refer to mount(1M) and mount_memfs(1M) for complete information on this filesystem-specific mount command.

A memfs filesystem is provided for each of /tmp and /var/tmp by default on systems with at least 100MB on their first drive. Files there do not need to survive crashes or reboots, so they can take advantage of a high-performance, volatile filesystem.

For more information on /tmp and /var/tmp, refer to ``Monitoring filesystem use''.