Re: UFS file system problem in either stable or current

On Sun, 2 Nov 2003, Valentin Nechayev wrote:
> Wed, Oct 22, 2003 at 03:14:33, strick (Dan Strick) wrote about "UFS file
> system problem in either stable or current":
> DS> There seems to be an inconsistency between release 4.9-RC and 5.1 ufs
> DS> support.  If I fsck the same ufs (type 1 of course) file system on
> DS> both releases, each claims that the other has left incorrect
> DS> summary data in the superblock.  Presumably only one can be correct.
> DS> I just don't know which to blame.
>
> Does this require explicit fsck?
> I have dual-booting between 4.9-release (and all previous 4.* releases earlier)
> and 5.1 (of 20030526) with shared disks and boot checking required in fstab;
> sometimes one of them crash and forced checking is made; neither 4.* nor 5.1
> claims superblock is bad.

You wouldn't notice after a crash.  The incompatibility turns out to be
the location and perhaps details of the "summary information" (e.g. number
of free blocks) in the superblock.  This does not affect the integrity of
the file system.  It does affect the output of the "df" command.

The first time you run fsck on a file system after modifying it
when running the other operating system, fsck will probably find
inconsistent super block summary data.  "fsck -p" will correct it
without asking (and might not even say much about it).

I recently read something in one of the FreeBSD newsgroups that
suggests that this incompatibility between 4.x and 5.x has in some
sense been corrected in -current.  I don't know any details.

See also:
	<http://www.freebsd.org/cgi/getmsg.cgi?fetch=446102+449665+/usr/local/www/db/text/2003/freebsd-current/20031102.freebsd-current>

Dan Strick
strick_at_covad.net