Date: Mon, 17 Feb 1997 13:23:14 -0800 From: "M.R.Murphy" <mrm@Mole.ORG> To: avalon@coombs.anu.edu.au, kuku@gilberto.physik.rwth-aachen.de Cc: hackers@freebsd.org, luigi@labinfo.iet.unipi.it, msmith@atrad.adelaide.edu.au Subject: Re: File system/disk recovery tools ? Message-ID: <199702172123.NAA26953@meerkat.mole.org>
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> > > >
> > > > actually an annoying thing with fsck -b is that I never know what
> > > > to use as an alternate superblock number. 32, says the manpage, is
> > > > an alternate superblock, but what are others ? I guess they depend
> > > > upon the geometry of the disk... is there a "magic" number that I
> > > > can look for ?
> > >
> > > You mean you didn't write them down when you made your filesystems? 8)
Ah, yes, I write them down each time :-) Never :-)
> > >
> > > Ok, presumably your disklabel is OK. Have a look in /sys/ufs/ffs/fs.h
> > > at the superblock layout; it's 8K long, has a fixed checksum, and
> > > contains various predictable fields (eg. the last mountpoint). This
> > > should let you hunt a copy of it down.
# disklabel -r wd0
or
# disklabel -r sd0
or whatever , depending upon the drive in use,
then
# newfs -N wd0a
or
# newfs -N sd0s1f
or whatever, depending upon the disk and partition.
Notice the "-N" switch :-)
Like this:
otchig# disklabel -r wd0
# /dev/rwd0c:
type: ESDI
disk: wd0s1
label:
flags:
bytes/sector: 512
sectors/track: 63
tracks/cylinder: 16
sectors/cylinder: 1008
cylinders: 2100
sectors/unit: 2116800
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0 # milliseconds
track-to-track seek: 0 # milliseconds
drivedata: 0
8 partitions:
# size offset fstype [fsize bsize bps/cpg]
a: 49152 0 4.2BSD 0 0 0 # (Cyl. 0 - 48*)
b: 262144 49152 swap # (Cyl. 48*- 308*)
c: 2116800 0 unused 0 0 # (Cyl. 0 - 2099)
e: 131072 311296 4.2BSD 0 0 0 # (Cyl. 308*- 438*)
f: 196608 442368 4.2BSD 0 0 0 # (Cyl. 438*- 633*)
g: 1477824 638976 4.2BSD 0 0 0 # (Cyl. 633*- 2099*)
otchig# newfs -N wd0g
Warning: 832 sector(s) in last cylinder unallocated
/dev/rwd0g: 1477824 sectors in 361 cylinders of 1 tracks, 4096 sectors
721.6MB in 23 cyl groups (16 c/g, 32.00MB/g, 7680 i/g)
super-block backups (for fsck -b #) at:
32, 65568, 131104, 196640, 262176, 327712, 393248, 458784, 524320, 589856, 655392, 720928, 786464, 852000, 917536, 983072,
1048608, 1114144, 1179680, 1245216, 1310752, 1376288, 1441824,
otchig#
Someday I'll remember to write down a few of the alternate superblocks.
Yeah, in my dreams... :-)
--
Mike Murphy mrm@Mole.ORG +1 619 598 5874
Better is the enemy of Good
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