Skip Navigation Links | |
Exit Print View | |
Oracle Solaris Administration: ZFS File Systems Oracle Solaris 11 Information Library |
1. Oracle Solaris ZFS File System (Introduction)
2. Getting Started With Oracle Solaris ZFS
3. Oracle Solaris ZFS and Traditional File System Differences
4. Managing Oracle Solaris ZFS Storage Pools
5. Managing ZFS Root Pool Components
6. Managing Oracle Solaris ZFS File Systems
7. Working With Oracle Solaris ZFS Snapshots and Clones
8. Using ACLs and Attributes to Protect Oracle Solaris ZFS Files
9. Oracle Solaris ZFS Delegated Administration
10. Oracle Solaris ZFS Advanced Topics
Using a ZFS Volume as a Swap or Dump Device
Using a ZFS Volume as an iSCSI LUN
Using ZFS on a Solaris System With Zones Installed
Adding ZFS File Systems to a Non-Global Zone
Delegating Datasets to a Non-Global Zone
Adding ZFS Volumes to a Non-Global Zone
Using ZFS Storage Pools Within a Zone
Managing ZFS Properties Within a Zone
Understanding the zoned Property
Copying Zones to Other Systems
11. Oracle Solaris ZFS Troubleshooting and Pool Recovery
12. Archiving Snapshots and Root Pool Recovery
13. Recommended Oracle Solaris ZFS Practices
When a pool is created, it is intrinsically tied to the host system. The host system maintains information about the pool so that it can detect when the pool is unavailable. Although useful for normal operations, this information can prove a hindrance when you are booting from alternate media or creating a pool on removable media. To solve this problem, ZFS provides an alternate root pool feature. An alternate root pool does not persist across system reboots, and all mount points are modified to be relative to the root of the pool.
The most common reason 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 zpool create -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
Pools can also be imported using an alternate root. This feature allows for recovery situations, where the mount points should not be interpreted in context of the current root, but under some temporary directory where repairs can be performed. This feature also can be used when you are mounting removable media as described in the preceding section.
In the following example, a pool called morpheus is imported with /mnt as the alternate root path. This example assumes that morpheus was previously exported.
# zpool import -R /a pool # zpool list morpheus NAME SIZE ALLOC FREE CAP HEALTH ALTROOT pool 44.8G 78K 44.7G 0% ONLINE /a # zfs list pool NAME USED AVAIL REFER MOUNTPOINT pool 73.5K 44.1G 21K /a/pool