Recovering the ZFS Root Pool or Root Pool Snapshots

The following sections describe how to perform the following tasks:

How to Replace a Disk in the ZFS Root Pool
How to Create Root Pool Snapshots
How to Re-create a ZFS Root Pool and Restore Root Pool Snapshots
How to Roll Back Root Pool Snapshots From a Failsafe Boot

How to Replace a Disk in the ZFS Root Pool

You might need to replace a disk in the root pool for the following reasons:

The root pool is too small and you want to replace a smaller disk with a larger disk.
A root pool disk is failing. In a non-redundant pool, if the disk is failing such that the system won't boot, you must boot from alternate media, such as a DVD or the network, before you replace the root pool disk.

In a mirrored root pool configuration, you can attempt a disk replacement without booting from alternate media. You can replace a failed disk by using the zpool replace command. Or, if you have an additional disk, you can use the zpool attach command. See the procedure in this section for an example of attaching an additional disk and detaching a root pool disk.

Some hardware requires that you take a disk offline and unconfigure it before attempting the zpool replace operation to replace a failed disk. For example:

# zpool offline rpool c1t0d0s0
# cfgadm -c unconfigure c1::dsk/c1t0d0
<Physically remove failed disk c1t0d0>
<Physically insert replacement disk c1t0d0>
# cfgadm -c configure c1::dsk/c1t0d0
# zpool replace rpool c1t0d0s0
# zpool online rpool c1t0d0s0
# zpool status rpool
<Let disk resilver before installing the boot blocks>
SPARC# installboot -F zfs /usr/platform/`uname -i`/lib/fs/zfs/bootblk /dev/rdsk/c1t0d0s0
x86# installgrub /boot/grub/stage1 /boot/grub/stage2 /dev/rdsk/c1t9d0s0

With some hardware, you do not have to online or reconfigure the replacement disk after it is inserted.

You must identify the boot device path names of the current disk and the new disk so that you can test booting from the replacement disk and also manually boot from the existing disk, if the replacement disk fails. In the example in the following procedure, the path name for the current root pool disk (c1t10d0s0) is:

/pci@8,700000/pci@3/scsi@5/sd@a,0

The path name for the replacement boot disk (c1t9d0s0) is:

/pci@8,700000/pci@3/scsi@5/sd@9,0

Physically connect the replacement (or new) disk.
Prepare the replacement disk for the root pool, if necessary.
- SPARC: Confirm that the disk has an SMI (VTOC) disk label and a slice 0. If you need to relabel the disk and create a slice 0, see Creating a Disk Slice for a ZFS Root File System in System Administration Guide: Devices and File Systems.
- x86: Confirm that the disk has an fdisk partition, an SMI disk label, and a slice 0. If you need to repartition the disk and create a slice 0, see Creating a Disk Slice for a ZFS Root File System in System Administration Guide: Devices and File Systems.
Attach the new disk to the root pool.
For example:
```
# zpool attach rpool c1t10d0s0 c1t9d0s0
```

Confirm the root pool status.

For example:

# zpool status rpool
  pool: rpool
 state: ONLINE
status: One or more devices is currently being resilvered.  The pool will
        continue to function, possibly in a degraded state.
action: Wait for the resilver to complete.
 scrub: resilver in progress, 25.47% done, 0h4m to go
config:

        NAME           STATE     READ WRITE CKSUM
        rpool          ONLINE       0     0     0
          mirror-0     ONLINE       0     0     0
            c1t10d0s0  ONLINE       0     0     0
            c1t9d0s0   ONLINE       0     0     0

errors: No known data errors

Verify that you can boot from the new disk.
For example, on a SPARC based system, you would use syntax similar to the following:
```
ok boot /pci@8,700000/pci@3/scsi@5/sd@9,0
```
If the system boots from the new disk, detach the old disk.
For example:
```
# zpool detach rpool c1t10d0s0
```
Set up the system to boot automatically from the new disk by resetting the default boot device.
- SPARC - Use the eeprom command or the setenv command from the SPARC boot PROM.
- x86 - Reconfigure the system BIOS.

How to Create Root Pool Snapshots

You can create root pool snapshots for recovery purposes. The best way to create root pool snapshots is to perform a recursive snapshot of the root pool.

The following procedure creates a recursive root pool snapshot and stores the snapshot as a file and as snapshots in a pool on a remote system. If a root pool fails, the remote dataset can be mounted by using NFS, and the snapshot file can be received into the re-created pool. You can also store root pool snapshots as the actual snapshots in a pool on a remote system. Sending and receiving the snapshots from a remote system is a bit more complicated because you must configure ssh or use rsh while the system to be repaired is booted from the Oracle Solaris OS miniroot.

Validating remotely stored snapshots as files or snapshots is an important step in root pool recovery. With either method, snapshots should be recreated on a routine basis, such as when the pool configuration changes or when the Solaris OS is upgraded.

In the following procedure, the system is booted from the zfsBE boot environment.

Create a pool and file system on a remote system to store the snapshots.
For example:
```
remote# zfs create rpool/snaps
```

Share the file system with the local system.

For example:

remote# zfs set sharenfs='rw=local-system,root=local-system' rpool/snaps
# share
-@rpool/snaps   /rpool/snaps   sec=sys,rw=local-system,root=local-system   ""

Create a recursive snapshot of the root pool.

local# zfs snapshot -r rpool@snap1
local# zfs list -r rpool
NAME                        USED  AVAIL  REFER  MOUNTPOINT
rpool                      7.84G  59.1G   109K  /rpool
rpool@snap1                  21K      -   106K  -
rpool/ROOT                 4.78G  59.1G    31K  legacy
rpool/ROOT@snap1               0      -    31K  -
rpool/ROOT/s10zfsBE        4.78G  59.1G  4.76G  /
rpool/ROOT/s10zfsBE@snap1  15.6M      -  4.75G  -
rpool/dump                 1.00G  59.1G  1.00G  -
rpool/dump@snap1             16K      -  1.00G  -
rpool/export                 99K  59.1G    32K  /export
rpool/export@snap1           18K      -    32K  -
rpool/export/home            49K  59.1G    31K  /export/home
rpool/export/home@snap1      18K      -    31K  -
rpool/swap                 2.06G  61.2G    16K  -
rpool/swap@snap1               0      -    16K  -

Send the root pool snapshots to the remote system.

For example, to send the root pool snapshots to a remote pool as a file, use syntax similar to the following:

local# zfs send -Rv rpool@snap1 > /net/remote-system/rpool/snaps/rpool.snap1
sending from @ to rpool@snap1
sending from @ to rpool/ROOT@snap1
sending from @ to rpool/ROOT/s10zfsBE@snap1
sending from @ to rpool/dump@snap1
sending from @ to rpool/export@snap1
sending from @ to rpool/export/home@snap1
sending from @ to rpool/swap@snap1

To send the root pool snapshots to a remote pool as snapshots, use syntax similar to the following:

local# zfs send -Rv rpool@snap1 | ssh remote-system zfs receive -Fd -o canmount=off tank/snaps
sending from @ to rpool@snap1
sending from @ to rpool/ROOT@snap1
sending from @ to rpool/ROOT/s10zfsBE@snap1
sending from @ to rpool/dump@snap1
sending from @ to rpool/export@snap1
sending from @ to rpool/export/home@snap1
sending from @ to rpool/swap@snap1

How to Re-create a ZFS Root Pool and Restore Root Pool Snapshots

In this procedure, assume the following conditions:

The ZFS root pool cannot be recovered.
The ZFS root pool snapshots are stored on a remote system and are shared over NFS.

All the steps are performed on the local system.

Boot from an installation DVD or the network.
- SPARC - Select one of the following boot methods:
```
ok boot net -s
ok boot cdrom -s
```
  If you don't use -s option, you'll need to exit the installation program.
- x86 – Select the option for booting from the DVD or the network. Then, exit the installation program.
Mount the remote snapshot file system if you have sent the root pool snapshots as a file to the remote system.
For example:
```
# mount -F nfs remote-system:/rpool/snaps /mnt
```
If your network services are not configured, you might need to specify the remote-system's IP address.
If the root pool disk is replaced and does not contain a disk label that is usable by ZFS, you must relabel the disk.
For more information about relabeling the disk, go to the following site:
http://www.solarisinternals.com/wiki/index.php/ZFS_Troubleshooting_Guide

Re-create the root pool.

For example:

# zpool create -f -o failmode=continue -R /a -m legacy -o cachefile=
/etc/zfs/zpool.cache rpool c1t1d0s0

Restore the root pool snapshots.
This step might take some time. For example:
```
# cat /mnt/rpool.0804 | zfs receive -Fdu rpool
```
Using the -u option means that the restored archive is not mounted when the zfs receive operation completes.
To restore the actual root pool snapshots that are stored in a pool on a remote system, use syntax similar to the following:
```
# rsh remote-system zfs send -Rb tank/snaps/rpool@snap1 | zfs receive -F rpool
```
Verify that the root pool datasets are restored.
For example:
```
# zfs list
```
Set the bootfs property on the root pool BE.
For example:
```
# zpool set bootfs=rpool/ROOT/zfsBE rpool
```

Install the boot blocks on the new disk.

SPARC:

# installboot -F zfs /usr/platform/`uname -i`/lib/fs/zfs/bootblk /dev/rdsk/c1t1d0s0

x86:

# installgrub /boot/grub/stage1 /boot/grub/stage2 /dev/rdsk/c1t1d0s0

Reboot the system.
```
# init 6
```

How to Roll Back Root Pool Snapshots From a Failsafe Boot

This procedure assumes that existing root pool snapshots are available. In the example, they are available on the local system.

# zfs snapshot -r rpool@snap1
# zfs list -r rpool
NAME                        USED  AVAIL  REFER  MOUNTPOINT
rpool                      7.84G  59.1G   109K  /rpool
rpool@snap1                  21K      -   106K  -
rpool/ROOT                 4.78G  59.1G    31K  legacy
rpool/ROOT@snap1               0      -    31K  -
rpool/ROOT/s10zfsBE        4.78G  59.1G  4.76G  /
rpool/ROOT/s10zfsBE@snap1  15.6M      -  4.75G  -
rpool/dump                 1.00G  59.1G  1.00G  -
rpool/dump@snap1             16K      -  1.00G  -
rpool/export                 99K  59.1G    32K  /export
rpool/export@snap1           18K      -    32K  -
rpool/export/home            49K  59.1G    31K  /export/home
rpool/export/home@snap1      18K      -    31K  -
rpool/swap                 2.06G  61.2G    16K  -
rpool/swap@snap1               0      -    16K  -

Shut down the system and boot failsafe mode.

ok boot -F failsafe
ROOT/zfsBE was found on rpool.
Do you wish to have it mounted read-write on /a? [y,n,?] y
mounting rpool on /a

Starting shell.

Roll back each root pool snapshot.

# zfs rollback rpool@snap1
# zfs rollback rpool/ROOT@snap1
# zfs rollback rpool/ROOT/s10zfsBE@snap1

Reboot to multiuser mode.
```
# init 6
```

Skip Navigation Links
Exit Print View
	Oracle Solaris ZFS Administration Guide Oracle Solaris 10 8/11 Information Library