Whenever you mount or unmount a file system, the /etc/mnttab (mount table) file is modified with the list of currently mounted file systems. You can display the contents of the mount table using the cat or more commands, but you cannot edit it. Here is an example of a /etc/mnttab file:
$ more /etc/mnttab /dev/dsk/c0t3d0s0 / ufs rw,suid,dev=800018,largefiles 863804345 /dev/dsk/c0t3d0s6 /usr ufs rw,suid,dev=80001e,largefiles 863804345 /proc /proc proc rw,suid,dev=2900000 863804345 fd /dev/fd fd rw,suid,dev=29c0000 863804345 /dev/dsk/c0t3d0s3 /export ufs suid,rw,largefiles,dev=80001b 863804347 /dev/dsk/c0t3d0s7 /export/home ufs suid,rw,largefiles,dev=80001f 863804348 /dev/dsk/c0t3d0s4 /export/swap ufs suid,rw,largefiles,dev=80001c 863804348 /dev/dsk/c0t3d0s5 /opt ufs suid,rw,largefiles,dev=80001d 863804347 swap /tmp tmpfs dev=2a80000 863804347 $ |