Date: Wed, 3 Dec 2003 15:39:02 +0200 From: Ion-Mihai Tetcu <itetcu@apropo.ro> To: scott@sremick.net Cc: FreeBSD <freebsd-questions@freebsd.org> Subject: Re: "Cannot find file system superblock" error - how to recover? Message-ID: <20031203153902.1d42b9d9.itetcu@apropo.ro> In-Reply-To: <20031203080612.54273.qmail@web41110.mail.yahoo.com> References: <20031203080612.54273.qmail@web41110.mail.yahoo.com>
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On Wed, 3 Dec 2003 00:06:12 -0800 (PST)
"Scott I. Remick" <scott@sremick.net> wrote:
> Running 5.1-REL on a system w/ 2 drives. Was saving a file to 2nd drive
> (mounts as /data) and system suddenly froze then rebooted. Never good. Fsck
> barfed on startup telling me I had to run it manually. The error I'm stuck
> with is:
>
> /dev/ad6s1c
> Cannot find file system superblock
> /dev/ad6s1c: NOT LABELED AS A BSD FILE SYSTEM
>
> Searching on this error hasn't been very productive. Some people talk about
> a "LOOK FOR ALTERNATE SUPERBLOCKS?" question that I'm not getting when I run
> fsck. There's also mention of an undocumented -b option to fsck for fixing
> this.
FSCK_FFS(8) FreeBSD System Manager's Manual FSCK_FFS(8)
NAME
fsck_ffs, fsck_ufs -- file system consistency check and interactive
repair
SYNOPSIS
fsck_ffs [-BFpfny] [-b block#] [-c level] [-m mode] filesystem ...
-b Use the block specified immediately after the flag as the super
block for the file system. Block 32 is usually an alternate
super block.
The key world is usually.
> Then there's some scary manual method using dd:
>
> dd if=/dev/ad6s1c skip=32 of=/dev/ad6s1c seek=16 bs=512 count=16
Try doing a newfs -N and see if using some of the alternatives
super-blocks in fsck_ufs will help. Note that the alternate superblock
is no longer always at 32, it depends on the size of the file system.
http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/ufs/ffs/fs.h?rev=1.39&content-type=text/x-cvsweb-markup
* Depending on the architecture and the media, the superblock may
* reside in any one of four places. For tiny media where every block
* counts, it is placed at the very front of the partition. Historically,
* UFS1 placed it 8K from the front to leave room for the disk label and
* a small bootstrap. For UFS2 it got moved to 64K from the front to leave
* room for the disk label and a bigger bootstrap, and for really piggy
* systems we check at 256K from the front if the first three fail. In
* all cases the size of the superblock will be SBLOCKSIZE. All values are
* given in byte-offset form, so they do not imply a sector size. The
* SBLOCKSEARCH specifies the order in which the locations should be searched.
*/
#define SBLOCK_FLOPPY 0
#define SBLOCK_UFS1 8192
#define SBLOCK_UFS2 65536
#define SBLOCK_PIGGY262144
#define SBLOCKSIZE 8192
#define SBLOCKSEARCH \
{ SBLOCK_UFS2, SBLOCK_UFS1, SBLOCK_FLOPPY, SBLOCK_PIGGY, -1 }
--
IOnut
Unregistered ;) FreeBSD user
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