Re: corrupt block makes file system repair impossible?

Theodore Y. Ts'o (tytso@MIT.EDU)
Wed, 9 Jul 1997 13:53:17 -0400

Date: Wed, 9 Jul 1997 17:53:22 +0200 (MET DST)
From: Thomas Koenig <>

I just tried to repair a file system on a disk with some bad sectors,
and e2fsck told me:

Block 4 in the primary group descriptors is on the bad block list

If the block is really bad, the filesystem can not be fixed.
You can clear the this block from the bad block list
and hope that block is really OK, but there are no guarantees.


Is this true? What's the point in having multiple superblocks if
trashing a single sector can still completely wreck your file system?

It's at least partially true. The kernel currently assumes that the
block group descriptors follow the superblock. If you specify another
superblock, it'll use another set of block group descriptors, though.

However, using an alternate superblock for a filesystem has typically
been viewed as a stopgap measure, instead of a something you would do as
a long-term thing. For example, there's no way to make fsck call e2fsck
with the right arguments to use an alternate superblock as part of the
default boot sequence for a particular filesystem (based on some fields
in fstab, for example). You can specify the alternate superblock if you
run e2fsck manually, and it's currently primarily used to recover from
problems where your primary superblock has been overwritten. But the
tools aren't currently set up to make this very easy.

- Ted