Recovering From Boot Problems

Because Solaris Volume Manager enables you to mirror the root (/), swap, and /usr directories, special problems can arise when you boot the system, either through hardware failures or operator error. The tasks in this section provide solutions to such potential problems.

The following table describes these problems and points you to the appropriate solution.

Background Information for Boot Problems

• If Solaris Volume Manager takes a volume offline due to errors, unmount all file systems on the disk where the failure occurred. Because each disk slice is independent, multiple file systems can be mounted on a single disk. If the software has encountered a failure, other slices on the same disk will likely experience failures soon. File systems mounted directly on disk slices do not have the protection of Solaris Volume Manager error handling, and leaving such file systems mounted can leave you vulnerable to crashing the system and losing data.

• Minimize the amount of time you run with submirrors disabled or offline. During resynchronization and online backup intervals, the full protection of mirroring is gone.

How to Recover From Improper /etc/vfstab Entries

If you have made an incorrect entry in the /etc/vfstab file, for example, when mirroring root (/), the system will appear at first to be booting properly then fail. To remedy this situation, you need to edit the /etc/vfstab file while in single-user mode.

The high-level steps to recover from improper /etc/vfstab file entries are as follows:

1. Booting the system to single-user mode

2. Running the fsck command on the mirror volume

3. Remounting file system read-write

4. Optional: running the metaroot command for a root (/) mirror

5. Verifying that the /etc/vfstab file correctly references the volume for the file system entry

6. Rebooting

Recovering the root (/) RAID 1 (Mirror) Volume

In the following example, root (/) is mirrored with a two-way mirror, d0. The root (/) entry in the /etc/vfstab file has somehow reverted back to the original slice of the file system, but the information in the /etc/system file still shows booting to be from the mirror d0. The most likely reason is that the metaroot command was not used to maintain the /etc/system and /etc/vfstab files, or an old copy of the/etc/vfstab file was copied back.

The incorrect /etc/vfstab file would look something like the following:

#device        device          mount          FS      fsck   mount    mount
#to mount      to fsck         point          type    pass   at boot  options
#
/dev/dsk/c0t3d0s0 /dev/rdsk/c0t3d0s0  /       ufs      1     no       -
/dev/dsk/c0t3d0s1 -                   -       swap     -     no       -
/dev/dsk/c0t3d0s6 /dev/rdsk/c0t3d0s6  /usr    ufs      2     no       -
#
/proc             -                  /proc    proc     -     no       -
swap              -                  /tmp     tmpfs    -     yes      -

Because of the errors, you automatically go into single-user mode when the system is booted:

ok boot
...
configuring network interfaces: hme0.
Hostname: lexicon
mount: /dev/dsk/c0t3d0s0 is not this fstype.
setmnt: Cannot open /etc/mnttab for writing

INIT: Cannot create /var/adm/utmp or /var/adm/utmpx

INIT: failed write of utmpx entry:"  "

INIT: failed write of utmpx entry:"  "

INIT: SINGLE USER MODE

Type Ctrl-d to proceed with normal startup,
(or give root password for system maintenance): <root-password>

At this point, root (/) and /usr are mounted read-only. Follow these steps:

Steps

1. Run the fsck command on the root (/) mirror.

   ---

   Note –

   Be careful to use the correct volume for root.

   ---

   # fsck /dev/md/rdsk/d0 ** /dev/md/rdsk/d0 ** Currently Mounted on / ** Phase 1 - Check Blocks and Sizes ** Phase 2 - Check Pathnames ** Phase 3 - Check Connectivity ** Phase 4 - Check Reference Counts ** Phase 5 - Check Cyl groups 2274 files, 11815 used, 10302 free (158 frags, 1268 blocks, 0.7% fragmentation)

2. Remount root (/) read/write so you can edit the /etc/vfstab file.

   # mount -o rw,remount /dev/md/dsk/d0 / mount: warning: cannot lock temp file </etc/.mnt.lock>

3. Run the metaroot command.

   # metaroot d0

   This command edits the /etc/system and /etc/vfstab files to specify that the root (/) file system is now on volume d0.

4. Verify that the /etc/vfstab file contains the correct volume entries.

   The root (/) entry in the /etc/vfstab file should appear as follows so that the entry for the file system correctly references the RAID 1 volume:

   #device device mount FS fsck mount mount #to mount to fsck point type pass at boot options # /dev/md/dsk/d0 /dev/md/rdsk/d0 / ufs 1 no - /dev/dsk/c0t3d0s1 - - swap - no - /dev/dsk/c0t3d0s6 /dev/rdsk/c0t3d0s6 /usr ufs 2 no - # /proc - /proc proc - no - swap - /tmp tmpfs - yes -

5. Reboot the system.

   The system returns to normal operation.

How to Recover From a Boot Device Failure

If you have a root (/) mirror and your boot device fails, you'll need to set up an alternate boot device.

The high-level steps in this task are as follows:

• Booting from the alternate root (/) submirror

• Determining the errored state database replicas and volumes

• Repairing the failed disk

• Restoring state database and volumes to their original state

In the following example, the boot device contains two of the six state database replicas and the root (/), swap, and /usr submirrors fails.

Initially, when the boot device fails, you'll see a message similar to the following. This message might differ among various architectures.

Rebooting with command:
Boot device: /iommu/sbus/dma@f,81000/esp@f,80000/sd@3,0   
The selected SCSI device is not responding
Can't open boot device
...

When you see this message, note the device. Then, follow these steps:

Steps

1. Boot from another root (/) submirror.

   Since only two of the six state database replicas in this example are in error, you can still boot. If this were not the case, you would need to delete the inaccessible state database replicas in single-user mode. This procedure is described in How to Recover From Insufficient State Database Replicas.

   When you created the mirror for the root (/) file system, you should have recorded the alternate boot device as part of that procedure. In this example, disk2 is that alternate boot device.

   ok boot disk2 SunOS Release 5.9 Version s81_51 64-bit Copyright 1983-2001 Sun Microsystems, Inc. All rights reserved. Hostname: demo ... demo console login: root Password: <root-password> Dec 16 12:22:09 lexicon login: ROOT LOGIN /dev/console Last login: Wed Dec 12 10:55:16 on console Sun Microsystems Inc. SunOS 5.9 s81_51 May 2002 ...

2. Determine that two state database replicas have failed by using the metadb command.

   # metadb flags first blk block count M p unknown unknown /dev/dsk/c0t3d0s3 M p unknown unknown /dev/dsk/c0t3d0s3 a m p luo 16 1034 /dev/dsk/c0t2d0s3 a p luo 1050 1034 /dev/dsk/c0t2d0s3 a p luo 16 1034 /dev/dsk/c0t1d0s3 a p luo 1050 1034 /dev/dsk/c0t1d0s3

   The system can no longer detect state database replicas on slice /dev/dsk/c0t3d0s3, which is part of the failed disk.

3. Determine that half of the root (/), swap, and /usr mirrors have failed by using the metastat command.

   # metastat d0: Mirror Submirror 0: d10 State: Needs maintenance Submirror 1: d20 State: Okay ... d10: Submirror of d0 State: Needs maintenance Invoke: "metareplace d0 /dev/dsk/c0t3d0s0 <new device>" Size: 47628 blocks Stripe 0: Device Start Block Dbase State Hot Spare /dev/dsk/c0t3d0s0 0 No Maintenance d20: Submirror of d0 State: Okay Size: 47628 blocks Stripe 0: Device Start Block Dbase State Hot Spare /dev/dsk/c0t2d0s0 0 No Okay d1: Mirror Submirror 0: d11 State: Needs maintenance Submirror 1: d21 State: Okay ... d11: Submirror of d1 State: Needs maintenance Invoke: "metareplace d1 /dev/dsk/c0t3d0s1 <new device>" Size: 69660 blocks Stripe 0: Device Start Block Dbase State Hot Spare /dev/dsk/c0t3d0s1 0 No Maintenance d21: Submirror of d1 State: Okay Size: 69660 blocks Stripe 0: Device Start Block Dbase State Hot Spare /dev/dsk/c0t2d0s1 0 No Okay d2: Mirror Submirror 0: d12 State: Needs maintenance Submirror 1: d22 State: Okay ... d2: Mirror Submirror 0: d12 State: Needs maintenance Submirror 1: d22 State: Okay ... d12: Submirror of d2 State: Needs maintenance Invoke: "metareplace d2 /dev/dsk/c0t3d0s6 <new device>" Size: 286740 blocks Stripe 0: Device Start Block Dbase State Hot Spare /dev/dsk/c0t3d0s6 0 No Maintenance d22: Submirror of d2 State: Okay Size: 286740 blocks Stripe 0: Device Start Block Dbase State Hot Spare /dev/dsk/c0t2d0s6 0 No Okay

   In this example, the metastat command shows that following submirrors need maintenance:

   • Submirror d10, device c0t3d0s0

   • Submirror d11, device c0t3d0s1

   • Submirror d12, device c0t3d0s6

4. Halt the system, replace the disk, and use the format command or the fmthard command, to partition the disk as it was before the failure.

   ---

   Tip –

   If the new disk is identical to the existing disk (the intact side of the mirror in this example), use prtvtoc /dev/rdsk/c0t2d0s2 | fmthard -s - /dev/rdsk/c0t3d0s2 to quickly format the new disk (c0t3d0 in this example)

   ---

   # halt ... Halted ... ok boot ... # format /dev/rdsk/c0t3d0s0

5. Reboot.

   Note that you must reboot from the other half of the root (/) mirror. You should have recorded the alternate boot device when you created the mirror.

   # halt ... ok boot disk2

6. To delete the failed state database replicas and then add them back, use the metadb command.

   # metadb flags first blk block count M p unknown unknown /dev/dsk/c0t3d0s3 M p unknown unknown /dev/dsk/c0t3d0s3 a m p luo 16 1034 /dev/dsk/c0t2d0s3 a p luo 1050 1034 /dev/dsk/c0t2d0s3 a p luo 16 1034 /dev/dsk/c0t1d0s3 a p luo 1050 1034 /dev/dsk/c0t1d0s3 # metadb -d c0t3d0s3 # metadb -c 2 -a c0t3d0s3 # metadb flags first blk block count a m p luo 16 1034 /dev/dsk/c0t2d0s3 a p luo 1050 1034 /dev/dsk/c0t2d0s3 a p luo 16 1034 /dev/dsk/c0t1d0s3 a p luo 1050 1034 /dev/dsk/c0t1d0s3 a u 16 1034 /dev/dsk/c0t3d0s3 a u 1050 1034 /dev/dsk/c0t3d0s3

7. Re-enable the submirrors by using the metareplace command.

   # metareplace -e d0 c0t3d0s0 Device /dev/dsk/c0t3d0s0 is enabled # metareplace -e d1 c0t3d0s1 Device /dev/dsk/c0t3d0s1 is enabled # metareplace -e d2 c0t3d0s6 Device /dev/dsk/c0t3d0s6 is enabled

   After some time, the resynchronization will complete. You can now return to booting from the original device.