Using ufsdump to backup a partition/slice

First,
$ df -k
to find the partition you want to back up

For example:
/dev/dsk/c1t0d0s0

Now simply type something like the following:
$ ufsdump 0f /backup/0_c1t1d0s0 /dev/dsk/c1t1d0s0

0 is the dump level
f means dump to file (default is stdout)
of course the file must not be on the partition you are backing up