System Administration Guide, Volume 1

Example--Creating a TMPFS File System at Boot Time

You can set up the system to automatically create a TMPFS file system when it boots by adding an entry to the /etc/vfstab file. The following example shows an entry in the /etc/vfstab file that will create a TMPFS file system on /export/test when the system boots. Since the size=number option is not specified, the size of the TMPFS file system on /export/test is limited only by the available system resources.

swap - /export/test  tmpfs   -  yes  -

For more information the /etc/vfstab file, see "The /etc/vfstab Field Descriptions".