Wednesday, April 4, 2012

Linux : How To Recover From Bad SuperBlock Corrupted Ext3 File System??

I was getting following error:



/dev/cciss/c0d0p1: Input/output error
mount: /dev/cciss/c0d0p1: can't read superblock

In case you are also facing the same error with superblocks, you can follow below given steps to recover superblock:

#### dumpe2fs  /dev/cciss/c0d0p1|grep -i superblock

dumpe2fs 1.39 (29-May-2006)
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super
  Primary superblock at 1, Group descriptors at 2-2
  Backup superblock at 8193, Group descriptors at 8194-8194
  Backup superblock at 24577, Group descriptors at 24578-24578
  Backup superblock at 40961, Group descriptors at 40962-40962
  Backup superblock at 57345, Group descriptors at 57346-57346
  Backup superblock at 73729, Group descriptors at 73730-73730


Above command output showing back'd up superblock. Now we need to restore from these superblocks


#### fsck -b 8193 /dev/cciss/c0d0p1

If still showing any error continue to restore with next Backup superblock i.e;  24577, 40961 etc....

After successful completion of above command i.e; output will be like this

Free blocks count wrong for group #362 (32254, counted=32248).
Fix? yes
Free blocks count wrong for group #368 (32254, counted=27774).
Fix? yes
..........

/dev/cciss/c0d0p1: ***** FILE SYSTEM WAS MODIFIED *****

 /dev/cciss/c0d0p1: 59586/30539776 files (0.6% non-contiguous), 3604682/61059048 blocks


Now mount your file system

##### mount  /dev/cciss/c0d0p1 /mnt


Thats it!!!

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