How are alternate superblocks repaired?

Andreas Dilger adilger at
Thu Sep 27 20:21:35 UTC 2007

On Sep 27, 2007  10:39 -0400, Thomas Watt wrote:
> I have written a metascript which generates a shell script to dump
> all of the superblock information you have requested, however, only
> the primary and first backup are compared and then the first backup
> is compared with the remaining bad backup superblocks.  That's not
> exactly what you requested, but will it suffice?

Seems fine.

Note that it may also be the backup group descriptors that are bad.
They are also only updated at e2fsck and online resize time.

> I understand that there was a previous kernel bug in the mount command regarding the -o sync option, and that it has been fixed in a subsequent release.  Consequently, I am for the moment not using that option on mounting the FC3 disk.  In what version of the kernel was the fix for the mount command -o sync bug?

Sorry, no idea.

> I suppose I still have a question that if the online resizing code is
> the only other code to touch the backup superblocks (out of necessity),
> then what is the recommended frequency on running e2fsck with what
> parameters to insure that the backup superblocks remain in good,
> usable condition?  Should this be done within FC3 natively in single
> user mode or will a Live CD environment with a newer version of e2fsck
> be more appropriate?

By default, e2fsck will be run on a filesystem every 20-40 mounts, or
6 months.  Some people turn that off, however.

Cheers, Andreas
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

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