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 this file by using the cat or more commands. However, you cannot edit this file. Here is an example of an /etc/mnttab file:
$ more /etc/mnttab rpool/ROOT/zfsBE / zfs dev=3390002 0 /devices /devices devfs dev=8580000 1337114941 /dev /dev dev dev=85c0000 1337114941 ctfs /system/contract ctfs dev=8680001 1337114941 proc /proc proc dev=8600000 1337114941 mnttab /etc/mnttab mntfs dev=86c0001 1337114941 swap /system/volatile tmpfs xattr,dev=8700001 1337114941 objfs /system/object objfs dev=8740001 1337114941 sharefs /etc/dfs/sharetab sharefs dev=8780001 1337114941 /usr/lib/libc/libc_hwcap2.so.1 /lib/libc.so.1 lofs dev=3390002 13371149 fd /dev/fd fd rw,dev=8880001 1337114969 rpool/ROOT/zfsBE/var /var zfs rw,devices, setuid,nonbmand,exec, rstchown,xattr,atime,dev=3390003 1337114969 swap /tmp tmpfs xattr,dev=8700002 1337114969 rpool/VARSHARE /var/share zfs rw,devices,setuid,nonbmand,exec, rstchown,xattr,atime,dev=3390004 1337114969