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AIX 5L Problem Determination - IBM Redbooks

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Fixing a bad superblock<br />

If you receive one of the following errors from the fsck or mount commands, the<br />

problem may be a corrupted superblock, as shown in the following example:<br />

fsck: Not an <strong>AIX</strong>3 file system<br />

fsck: Not an <strong>AIX</strong>V3 file system<br />

fsck: Not an <strong>AIX</strong>4 file system<br />

fsck: Not an <strong>AIX</strong>V4 file system<br />

fsck: Not a recognized file system type<br />

mount: invalid argument<br />

The problem can be resolved by restoring the backup of the superblock over the<br />

primary superblock using the following command (care should be taken to check<br />

with the latest product documentation before running this command):<br />

# dd count=1 bs=4k skip=31 seek=1 if=/dev/lv00 of=/dev/lv00<br />

The following is an example of when the superblock is corrupted and copying the<br />

backup helps solve the problem:<br />

# mount /u/testfs<br />

mount: 0506-324 Cannot mount /dev/lv02 on /u/testfs: A system call received a<br />

parameter that is not valid.<br />

# fsck /dev/lv02<br />

Not a recognized filesystem type. (TERMINATED)<br />

# dd count=1 bs=4k skip=31 seek=1 if=/dev/lv02 of=/dev/lv02<br />

1+0 records in.<br />

1+0 records out.<br />

# fsck /dev/lv02<br />

** Checking /dev/lv02 (/u/tes)<br />

** Phase 0 - Check Log<br />

log redo processing for /dev/lv02<br />

** Phase 1 - Check Blocks and Sizes<br />

** Phase 2 - Check Pathnames<br />

** Phase 3 - Check Connectivity<br />

** Phase 4 - Check Reference Counts<br />

** Phase 5 - Check Inode Map<br />

** Phase 6 - Check Block Map<br />

8 files 2136 blocks 63400 free<br />

Once the restoration process is complete, check the integrity of the file system by<br />

issuing the fsck command:<br />

# fsck /dev/lv00<br />

Chapter 7. LVM, file system, and disk problem determination 153

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