You can use Fast Reboot to directly mount a root (/) disk or root dataset, then reboot to it:

1. Become superuser or assume an equivalent role.
2. Mount the root (/) disk.
   For example:

   # mount /dev/dsk/c1d0s0 /mnt
   

3. To mount a root dataset, type:

   # zfs mount rpool/dataset
   

4. Reboot the mounted disk or mounted dataset.
   For example:

   # reboot -f -- '/mnt/platform/i86pc/kernel/amd64/unix'