The most common use for creating an alternate root pool is for use with removable media. In these circumstances, users typically want a single file system, and they want it to be mounted wherever they choose on the target system. When an alternate root pool is created by using the -R option, the mount point of the root file system is automatically set to /, which is the equivalent of the alternate root value.
In the following example, a pool called morpheus is created with /mnt as the alternate root path:
# zpool create -R /mnt morpheus c0t0d0 # zfs list morpheus NAME USED AVAIL REFER MOUNTPOINT morpheus 32.5K 33.5G 8K /mnt |
Note the single file system, morpheus, whose mount point is the alternate root of the pool, /mnt. The mount point that is stored on disk is / and the full path to /mnt is interpreted only in this initial context of the pool creation. This file system can then be exported and imported under an arbitrary alternate root pool on a different system by using -R alternate root value syntax.
# zpool export morpheus # zpool import morpheus cannot mount '/': directory is not empty # zpool export morpheus # zpool import -R /mnt morpheus # zfs list morpheus NAME USED AVAIL REFER MOUNTPOINT morpheus 32.5K 33.5G 8K /mnt |