Solaris – How to Recover a Corrupted Disk Label

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Sometimes, a power or system failure causes a disk’s label to become unrecognizable. A corrupted disk label doesn’t always mean that the slice information or the disk’s data must be re-created or restored.

The first step to recovering a corrupted disk label is to label the disk with the correct geometry and disk type information. You can complete this step through the normal disk labeling method, by using either automatic configuration or manual disk type specification.

If the format utility recognizes the disk type, the next step is to search for a backup label to label the disk. Labeling the disk with the backup label labels the disk with the correct partitioning information, the disk type, and disk geometry.

Steps to Recover Corrupted Disk Label

  1. Boot the system to single-user mode.If necessary, boot the system from a local Oracle Solaris DVD or the network in single-user mode to access the disk.
  2. Relabel the disk.
    # format

    The format utility attempts to automatically configure any unlabeled SCSI disk. If the format utility is able to configure the unlabeled and corrupted disk, it will display this message:

    cwtxdy: configured with capacity of abcMB

    The format utility then displays a numbered list of disks on the system.

  3. Type the number of the disk that you need to recover.
    Specify disk (enter its number): 1
  4. Select one of the following to determine how to label the disk.
    • If the disk was configured successfully, do the following:
      1. Search for the backup label.
        format> verify
        Warning: Could not read primary label.
        Warning: Check the current partitioning and 'label' the disk or 
        use the 'backup' command.
        Backup label contents:
        Volume name = <        >
        ascii name  = <FUJITSU-MAP3147N SUN146G-0501>
        pcyl        = 14089
        ncyl        = 14087
        acyl        =    2
        nhead       =   24
        nsect       =  848
        Part      Tag    Flag     Cylinders         Size            Blocks
          0       root    wm       0 - 14086      136.71GB    (14087/0/0) 286698624
          1       swap    wu       0                0         (0/0/0)             0
          2     backup    wu       0 - 14086      136.71GB    (14087/0/0) 286698624
          3 unassigned    wm       0                0         (0/0/0)             0
          4 unassigned    wm       0                0         (0/0/0)             0
          5 unassigned    wm       0                0         (0/0/0)             0
          6        usr    wm       0                0         (0/0/0)             0
          7 unassigned    wm       0                0         (0/0/0)             0
      2. If the format utility was able to find a backup label, and the backup label contents appear satisfactory, label the disk with the backup label.
        format> backup
        Disk has a primary label, still continue? y
         
        Searching for backup labels...found.
        Restoring primary label

        The disk label has been recovered

      3. Exit the format utility.
        format> q
    • If the disk was not configured successfully, do the following:
      1. Specify the disk type by using the type command:
        format> type

        The Available Drives Type menu is displayed.

      2. Select 0 to automatically configure the disk. Or, select a disk type from the list of possible disk types.
        Specify disk type (enter its number)[12]: 12
      3. If the disk was successfully configured, reply with no when the format utility asks if you want to label the disk.
        Disk not labeled.  Label it now?  no
      4. Search for the backup label.
        format> verify
        Warning: Could not read primary label.
        Warning: Check the current partitioning and 'label' the disk
        or use the 'backup' command.
        .
        .
        .
      5. If the format utility was able to find a backup label, and the backup label contents appear satisfactory, label the disk with the backup label.
        format> backup
        Disk has a primary label, still continue? y
        Searching for backup labels...found.
        Restoring primary label

        The disk label has been recovered.

      6. Exit the format utility.
        format> q
  5. Verify the file systems on the recovered disk.

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