'Values in super block disagree with...' BSD Error and Recovery

Published: 22nd September 2009
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The UFS Superblock contains the basic configuration and size information of file system. UFS1 Superblock is located at sector 16 of the hard disk with 2,048 bytes allocated to it. UFS2 super block is found to be little simpler and removes many unused fields. It is located at sector 128 of the hard disk. A BSD system cannot boot if its super block is corrupted. In such cases, you might come across errors which suggest you running fsck manually. The command looks for alternative super block to repair the corrupted volume and hence to allow the system to boot. But if the command fails to repair the volume, your data will remain inaccessible. To recover this lost data, you need to use BSD Data Recovery that can extract the lost data.



For an instance, consider that you use a BSD based computer system. When you boot the system, you observe that the auto file system check process and you come across the similar error message:



"/dev/da0s1a: BAD SUPER BLOCK: VALUES IN SUPER BLOCK DISAGREE WITH

THOSE IN FIRST ALTERNATE

/dev/da0s1a: UNEXPECTED INCONSISTENCY: RUN fsck MANUALLY"




After this, the auto file system check process fails and the boot process halts. You experience that the system is put in single user mode. This issue might occur both in UFS1 or UFS2 file system.



Cause



The prime cause of this error to occur is that the super block is corrupted. This could occur due to any of the following possible reasons:



Unexpected system shutdown

You are using UFS1 file system and have installed FreeBSD 5.x and FreeBSD 4.x on the same system. The issue might occur if you try to mount 4.x partition under 5.x because they possess different super block format



Solution



To solve the existing issue, run the following commands:



/sbin/fsck -y /dev/da0s1a



/sbin/fsck -p




If the commands run successfully, you will be able to boot into the system. But if it doesn't, you need to either use your backup or scan the disk using a powerful BSD Recovery utility to recover the data. BSD Data Recovery product employ advanced algorithms to locate and recover lost data after any logical crash case.



Stellar Phoenix BSD- Data Recovery is a powerful utility that recovers and restores lost data from UFS1 and UFS2 file system. It is a comprehensive BSD Recovery product that is supportive to FreeBSD, OpenBSD and NetBSD variants. It is an easy-to-use tool embedded with advanced options.

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