Hi,
(apologies in advance if this is the wrong place to post this, but the
e2fsprogs mailing list on sf seems to be dead).
I have a machine that dual boots NetBSD-current and Ubuntu 10.04.2 LTS so /home is ext2
for it to work with both.
A while ago (i think after an ubuntu release upgrade) the netbsd ext2 fsck
started to core dump when checking /home. I checked the fs with the fsck
from e2fsprogs and it passed so i assumed it was a netbsd bug and
ignored it.
Recently i came back to the problem intending to fix netbsd's ext2 fsck
and discovered that all the backup super blocks on the fs where compleatly
zeroed out.
If the e2fs progs fsck can't find the first backup superblock it checks
the 2nd one and so on, but it exits cleanly if it dosen't find any.
I assume that not having any backup super blocks is a bad thing and the
e2fsprogs fsck should check for that case and offer to copy the main
superblock to all the backup positions.
Here's the output of fsck patched to print the block groups (bg) and block
numbers of where it's trying to find super blocks, the ignoreing happens
if the (backup_sb->s_magic != EXT2_SUPER_MAGIC) || (backup_sb->s_rev_level >
EXT2_LIB_CURRENT_REV) || [other stuff] test fails in e2fsck/super.c,
line 930 ish:
root@limpit:~/e2fs/e2fsprogs-1.41.11/e2fsck# ./e2fsck /dev/sda3
e2fsck 1.41.11 (14-Mar-2010)
looking for backup sb at blk 32768 (bg 1)
ignoring backup sb at blk 32768
looking for backup sb at blk 98304 (bg 3)
ignoring backup sb at blk 98304
looking for backup sb at blk 163840 (bg 5)
ignoring backup sb at blk 163840
looking for backup sb at blk 229376 (bg 7)
ignoring backup sb at blk 229376
looking for backup sb at blk 294912 (bg 9)
ignoring backup sb at blk 294912
looking for backup sb at blk 819200 (bg 25)
ignoring backup sb at blk 819200
looking for backup sb at blk 884736 (bg 27)
ignoring backup sb at blk 884736
looking for backup sb at blk 1605632 (bg 49)
ignoring backup sb at blk 1605632
looking for backup sb at blk 2654208 (bg 81)
ignoring backup sb at blk 2654208
looking for backup sb at blk 4096000 (bg 125)
ignoring backup sb at blk 4096000
looking for backup sb at blk 7962624 (bg 243)
ignoring backup sb at blk 7962624
looking for backup sb at blk 11239424 (bg 343)
ignoring backup sb at blk 11239424
looking for backup sb at blk 20480000 (bg 625)
ignoring backup sb at blk 20480000
looking for backup sb at blk 23887872 (bg 729)
ignoring backup sb at blk 23887872
WARNING: no backup superblocks found
Home: clean, 1047277/7806976 files, 21507366/31208652 blocks
I've saved each backup superblock to a file and confirmed that they are
all zero's (0x00).
If i use findsuper on the partition i get:
root@limpit:~/e2fs/e2fsprogs-1.41.11/misc# ./findsuper /dev/sda3
starting at 0, with 512 byte increments
byte_offset byte_start byte_end fs_blocks blksz grp last_mount_time sb_uuid label
1024 0 127830638592 31208652 4096 0 Fri Jun 24 19:00:34 2011 8e19240c Home
34359738368 44452740608 44452739584 2051003513344 1959522240 1024 0 Wed Feb 4 15:42:08 2032 1c000000 E
67366390784 18314584675153709056 18314584675153709056 0 1024 38051 Sun May 11 07:34:55 1952 f7fff7ff
89764110848 89764109824 89768720896 4503 1024 0 Thu Jan 1 01:00:00 1970 00000000
89768768000 89768766976 89785544192 16384 1024 0 Thu Jan 1 01:00:00 1970 00000000
89790432256 89790431232 89854443520 62512 1024 0 Thu Jun 12 09:47:43 1980 4608c91f
89799914496 89791524864 89855537152 62512 1024 1 Thu Jan 1 01:00:00 1970 4608c91f
89816708096 89791541248 89855553536 62512 1024 3 Thu Jan 1 01:00:00 1970 4608c91f
89833501696 89791557632 89855569920 62512 1024 5 Thu Jan 1 01:00:00 1970 4608c91f
89850295296 89791574016 89855586304 62512 1024 7 Thu Jan 1 01:00:00 1970 4608c91f
104213687296 104213686272 104217880576 4096 1024 0 Sun Dec 31 14:46:17 2006 3acdc9d5
124554051584: 220752kB/s @ Fri Jun 24 19:45:34 2011
127830640640: finished with errno 2
[the output above was captured with typescript, it got slightly mangled].
Apart from the 1st one, which is valid, i don't think any of the other
superblocks are relevent, in particular the blocksize should be 4096, and
the dates are bogus. The sequence of superblocks with 62512 fs_blocks and
4608c91f sb_uuid might be from a filesystem image, but it's too small to be
my /home.
Does anyone know what could cause the lack of backup super blocks to
happen?
Has anyone heard of this happening to anyone else?
P.S. see also related netbsd problem report: http://gnats.netbsd.org/45072
--
[http://pointless.net/] [0x2ECA0975]
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