Problem Booting (Bad Super Block)

[Matthew Seaman]

On Fri, Nov 28, 2003 at 12:56:02AM -0800, Rishi Chopra wrote:
> I've started having problems on my FreeBSD box; I've installed FreeBSD 
> on this system at least 5 times before without any problems.
> 
> This time, the installation took many attempts, and the following error 
> message occurs when I attempt to boot up:
> 
> /dev/da0s1a:  BAD SUPER BLOCK:  VALUES IN SUPER BLOCK DISAGREE WITH 
> THOSE IN FIRST ALTERNATE
> /dev/da0s1a:  UNEXPECTED INCONSISTENCY:  RUN fsck MANUALLY
> 
> Automatic file system check then fail, the boot process aborts, and the 
> system starts in single user mode.
> 
> How can I fix this error so that the machine boots normally?  I am 
> unable to run fsck from the prompt by just typing 'fsck'....

First thing you have to do is run fsck manually, like it says:

    # /sbin/fsck -y /dev/da0s1a

With luck, this will fix the problems with your filesystem.  Now, make
sure that the rest of your filesystems are clean:

    # /sbin/fsck -p

and then you should be able to reboot successfully.

If you can't run /sbin/fsck then you must be running FreeBSD 5.x with
the dynamic root patches.  In this case, there should be a statically
linked copy of fsck in /recover (? -- can't remember exactly what
directory is used, but it's something like that).  

The question remains as to why you're seeing this problem.  There are
3 obvious possibilities I can think of:

    i) You didn't shut down cleanly -- however, normally the automatic
       fsck on reboot should clear up any problems.  If you're
       exceedingly unlucky, you might kill the system right in the
       middle of a critical operation and leave the disk in a nasty
       state leading to the effects you've seen.  In this case, once
       you've cleared up this time, you shouldn't suffer from the
       problem again.

   ii) Your disk is failing.

  iii) You've got (or once had) FreeBSD 5.x installed on the same
       system and you mount your 4.x partitions under 5.x -- there
       have been changes to the superblock format in UFS1 between 4.x
       and 5.x:

       http://www.freebsd.org/cgi/query-pr.cgi?pr=54884

	Cheers,

	Matthew

-- 
Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
PGP: http://www.infracaninophile.co.uk/pgpkey         Marlow
Tel: +44 1628 476614                                  Bucks., SL7 1TH UK
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