Booting into the BDA Rescue Image Shows Boot and Root have Superblock Corruptions

Asset ID:	1-72-2142995.1
Update Date:	2017-06-16
Keywords:

Solution Type Problem Resolution Sure

Solution 2142995.1 : Booting into the BDA Rescue Image Shows Boot and Root have Superblock Corruptions

Applies to:

Big Data Appliance X5-2 Hardware - Version All Versions and later
Linux x86-64

Symptoms

Booting using the BDA rescue image shows boot and root have superblock corruptions.

After booting into the BDA rescue image in this case:

/dev/md0 boot is md127
/dev/md2 root is md126

The superblock is corrupted on both volumes.

# mount /dev/md126 /mnt

EXT4-fs (md126): ext4_check_descriptors: Block bitmap for group 3072 not in group (block 334598144)!
EXT4-fs (md126): group descriptors corrupted!
mount: wrong fs type, bad option, bad superblock on /dev/md126,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so

# mount /dev/md127 /mnt

EXT4-fs (md127): ext4_check_descriptors: Block bitmap for group 0 not in group (block 1050624)!
EXT4-fs (md127): group descriptors corrupted!
mount: wrong fs type, bad option, bad superblock on /dev/md127,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so

Cause

The cause is not known.

Solution

1. You can try:

# mkfs.ext4 -S /dev/md126
# mkfs.ext4 -S /dev/md127

but there can be data loss.

The -S option will allow you to write superblock and groups descriptions.

-S Write superblock and group descriptors only. This is useful if all of the superblock and backup superblocks are corrupted, and a last-ditch recovery method is desired. It causes mke2fs to reinitialize the superblock and group descriptors, while not touching the inode table and the block and inode bitmaps. The e2fsck program should be run immediately after this option is used, and there is no guarantee that any data will be salvageable. It is critical to specify the correct filesystem blocksize when using this option, or there is no chance of recovery.

2. The recommendation is to first try the options in, How to Check and Repair EXT3/EXT4 Filesystem on Oracle Linux (Doc ID 1666661.1), to use fsck and try to recover the filesystem using other superblocks. Make sure that you take a file system backup first.

Note: Sometime the level of corruption is so intense that it becomes hard to recover and in that case you will have to loose your data and rebuild the filesystem.

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