The fifth field, (fs_freq), is used for these filesystems by the
dump(8) command to determine which filesystems need to be dumped.
If the fifth field is not present, a value of zero is returned and
dump will assume that the filesystem does not need to be dumped.
The sixth field, (fs_passno), is used by the fsck(8) program to determine
the order in which filesystem checks are done at reboot
time. The root filesystem should be specified with a fs_passno of 1, and
other filesystems should have a fs_passno of 2. Filesystems within a
drive will be checked sequentially, but filesystems on different drives
will be checked at the same time to utilize parallelism available in
the hardware. If the sixth field is not present or zero, a value of
zero is returned and fsck will assume that the filesystem does not
need to be checked.