recovering FC3 from a bad superblock

[Derek Martin]

I'm going to take a second crack at this since my first reply left a
lot to be desired.  Ben's was much better, but there's some other
stuff that may be useful here too.

On Mon, May 16, 2005 at 01:23:37PM -0400, Greg Rundlett wrote:
> Using the so-called backup superblocks [block-size (8192 *n) +1], it
> reports a 'bad magic number'
> e2fsck -b 16384 -n /dev/hda2

Your partition is probably sufficiently large that you're using a 4K
block size, rather than a 2K block size, so if this is still an issue
for you, you can try this instead:

  fsck -b 32768 -a -f /dev/hda2

Most likely the defaults were used when the filesystem was made, so
you can find out where other superblocks are with mke2fs:

  (UNMOUNT THE FILESYSTEM FIRST!)
  mke2fs -n /dev/hda2

BE VERY CAREFUL typing this command.  If you leave off the -n, your
existing filesystem will be destroyed!

> How should I go about fixing the 'errors' while the filesystem is not
> mounted?  Or, how should I mount the filesystem properly so that it
> can be fixed, but not 'used' during the fix?

You should leave the filesystem unmounted, as Ben said...  Though it
isn't harmful to mount it read-only.  Since this is your root
partition, it's useful to know how to do that.  If it's mounted
already, you need to use the remount option:

  mount -o remount,ro /dev/hda2 <mountpoint>

Note that mount options (after -o) are comma separated and must
contain no spaces.

If it's not already mounted, just leave off the remount, and you're
all set.  But since you're booting from rescue CD, there's no real
reason to have it mounted at all.

-- 
Derek D. Martin    http://www.pizzashack.org/   GPG Key ID: 0xDFBEAD02
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