The following taken from Sunsolve - ( moving filesystems and boot devices with ufsdump and ufsrestore) - the steps not needed for your question were removed.


Step 1: Perform a complete system backup.


Step 2: Use format (see man format) to create the partitions wanted on the target drive. (NOTE: /opt is not a legal tag so this partition's tag will be unassigned.)

c0t2d0s0 root
c0t2d0s1 swap
c0t2d0s2 backup
c0t2d0s3 unassigned
c0t2d0s4 unassigned
c0t2d0s5 unassigned (opt)
c0t2d0s6 usr
c0t2d0s7 var

Step 3: Label the disk when partitioning is complete. Exit format.

Step 4: newfs each of the partitions on the target drive.
# newfs /dev/rdsk/c0t2d0s0
# newfs /dev/rdsk/c0t2d0s5
# newfs /dev/rdsk/c0t2d0s6
# newfs /dev/rdsk/c0t2d0s7


Step 5: Mount each of the new filesystems from the source drive. (not needed for swap and backup)
# mount /dev/dsk/c0t2d0s0 /newroot
# mount /dev/dsk/c0t2d0s5 /newopt
# mount /dev/dsk/c0t2d0s6 /newusr
# mount /dev/dsk/c0t2d0s7 /newvar


Step 6: Update /etc/vfstab
This is the target /etc/vfstab.

#device device mount FS fsck mount mount
#to mount to fsck point type pass at boot options
#
#/dev/dsk/c1d0s2 /dev/rdsk/c1d0s2 /usr ufs 1 yes -
fd - /dev/fd fd - no -
/proc - /proc proc - no -
/dev/dsk/c0t2d0s1 - - swap - no -
/dev/dsk/c0t2d0s0 /dev/rdsk/c0t2d0s0 / ufs 1 no
-
/dev/dsk/c0t2d0s5 /dev/rdsk/c0t2d0s3 /opt ufs 2 yes
-
/dev/dsk/c0t2d0s6 /dev/rdsk/c0t2d0s3 /usr ufs 2 yes
-
/dev/dsk/c0t2d0s7 /dev/rdsk/c0t2d0s7 /var ufs 2 yes
-
swap - /tmp tmpfs - yes -