How to Recover a Corrupted Disk Label (System Administration Guide: Devices and File Systems)

System Administration Guide: Devices and File Systems

How to Recover a Corrupted Disk Label

Steps

Boot the system to single-user mode.

If necessary, boot the system from a local CD-ROM or the network in single-user mode to access the disk.

See Chapter 10, Booting a System (Tasks), in System Administration Guide: Basic Administration or Chapter 11, Booting a System (Tasks), in System Administration Guide: Basic Administrationfor information on booting the system.

Relabel the disk.
# format
At this point, 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:
cwtxdy: configured with capacity of abcMB
The format utility then displays the list of disks on the system.

Type the number of the disk that you need to recover from the list displayed on your screen.
Specify disk (enter its number): 1

Select one of the following to determine how to label the disk.
1. If the disk was configured successfully, follow steps 5 and 6. Then go to step 12.
2. If the disk was not configured successfully, follow steps 7-11. Then go to step 12.

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  = <SUN1.05 cyl 2036 alt 2 hd 14 sec 72>
pcyl        = 2038
ncyl        = 2036
acyl        =    2
nhead       =   14
nsect       =   72
Part      Tag    Flag     Cylinders        Size            Blocks
  0       root    wm       0 -  300      148.15MB    (301/0/0)   303408
  1       swap    wu     301 -  524      110.25MB    (224/0/0)   225792
  2     backup    wm       0 - 2035     1002.09MB    (2036/0/0) 2052288
  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     525 - 2035      743.70MB    (1511/0/0) 1523088
  7 unassigned    wm       0               0         (0/0/0)          0

If the format utility was able to find a backup label and the backup label contents appear satisfactory, use the backup command to 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. Go to step 12.

If the format utility was not able to automatically configure the disk, specify the disk type by using the type command.
format> type
The Available Drives Type menu is displayed.

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

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

Use the verify command to search for backup labels.

format> verify
Warning: Could not read primary label.
Warning: Check the current partitioning and 'label' the disk
or use the 'backup' command.
.
.
.

If the format utility was able to find a backup label and the backup label contents appear satisfactory, use the backup command to 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.

Exit the format utility.
format> q

Verify the file systems on the recovered disk by using the fsck command.

For information on using the fsck command, see Chapter 20, Checking UFS File System Consistency (Tasks).