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4.2 File System Types

4.2.1 Temporary File System (tmpfs)

A temporary file system uses memory to simulate a traditional disk partition. Normal file system writes are scheduled to be written to disk along with access control information, but the files actually reside in memory only.

A good candidate for a tmpfs is a partition that will have many small files that will be accessed often, e.g. /tmp. This will considerably speed up their access time. Tmpfs files and directories are NOT saved when the system shuts down.

Tmpfs is recommended for systems that do a lot of compiling and loading of programs and have large amounts of memory (> 16 MB) and swap space.

Disadvantages are that it reduces the amount of swap space available for other process and that it is volatile.

To mount a temporary file system under SunOS 4.1.X as /tmp:

# mount -t tmp swap /tmp

where the -t option indicates the type is tmp.

Do do this under SunOS 5.X you specify the -F option:

# mount -F tmpfs swap /tmp

Note that the file system type is specified as tmp in SunOS 4.1.X and tmpfs in SunOS 5.X.

In order to use tmpfs under SunOS 4.1.X the TMPFS option must be configured in the kernel, and an entry such as:

swap /tmp tmp rw 0 0

could be put in /etc/fstab.

Under SunOS 5.X the /etc/vfstab entry would look like:

#device device mount FS fsck mount mount
#to mount to fsck point type pass at boot options
swap - /tmp tmpfs - yes -

Unix System Administration - 8 AUG 1996
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