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temporary_user n00b
Joined: 26 Aug 2012 Posts: 37
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Posted: Thu Jul 25, 2013 5:22 pm Post subject: partition failure after power loss |
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Hello!
After a recent power loss my Gentoo system stopped booting and displayed kernel panic instead. It turns out that my root partition can't be mounted. I've used SystemRescueCD to scan partition for errors while it was unmounted, but I got a "bad superblock" error. I've already tried to use backup superblocks, but it didn't help.
Code: | Model: ATA OCZ-VERTEX4 (scsi)
Disk /dev/sda: 128GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name
Flags
1 1049kB 316MB 315MB ntfs Basic data partition hidden, diag
2 316MB 420MB 105MB fat32 EFI system partition boot
3 420MB 555MB 134MB Microsoft reserved partition msftres
4 555MB 80.5GB 80.0GB ntfs Basic data partition
5 80.5GB 128GB 47.5GB |
Code: | root@sysresccd /root % mke2fs -n /dev/sda5
mke2fs 1.42.7 (21-Jan-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
2899968 inodes, 11597568 blocks
579878 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=0
354 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632,
2654208, 4096000, 7962624, 11239424 |
When I use e2fsck with blocks 32768 to 29491 it gives me "bad magic number in superblock", other values return "invalid argument".
Code: | root@sysresccd /root % e2fsck -b 32768 /dev/sda5
e2fsck 1.42.7 (21-Jan-2013)
e2fsck: Bad magic number in super-block while trying to open /dev/sda5
The superblock could not be read or does not describe a correct ext2
filesystem. If the device is valid and it really contains an ext2
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
e2fsck -b 8193 <device>
root@sysresccd /root % e2fsck -b 819200 /dev/sda5
e2fsck 1.42.7 (21-Jan-2013)
e2fsck: Invalid argument while trying to open /dev/sda5
The superblock could not be read or does not describe a correct ext2
filesystem. If the device is valid and it really contains an ext2
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
e2fsck -b 8193 <device> |
Thank you in advance for all your help,
temporary_user |
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eccerr0r Watchman
Joined: 01 Jul 2004 Posts: 9679 Location: almost Mile High in the USA
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Posted: Thu Jul 25, 2013 6:44 pm Post subject: |
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Check your dmesg (1) to see if Linux is having problems reading your SSD... It may have croaked :( _________________ Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching? |
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temporary_user n00b
Joined: 26 Aug 2012 Posts: 37
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Posted: Thu Jul 25, 2013 10:10 pm Post subject: |
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I guess the disk is fine (except for this one partition) - right now I'm writing from Windows Server 2012, which is sda4. |
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NeddySeagoon Administrator
Joined: 05 Jul 2003 Posts: 54237 Location: 56N 3W
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Posted: Thu Jul 25, 2013 10:34 pm Post subject: |
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temporary_user,
Code: | Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632,
2654208, 4096000, 7962624, 11239424 |
And Code: | Block size=4096 (log=2) | need to be read together when you specifiy an alternate superblock.
Disk software works with 1k blocks, but alternate superblock numbers are in filesystem blocks, in this case 4k.
extX can also use 1k and 2k filesystem blocks.
It is documented but not where you would expect. Read man mount, ext2 options, sb=
Having pointed to that, before you use fsck, try Code: | mount -o ro,sb=131072 /dev/sda5 /mnt/gentoo |
You don't want to mount a damaged fs rw. _________________ Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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temporary_user n00b
Joined: 26 Aug 2012 Posts: 37
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Posted: Fri Jul 26, 2013 8:35 am Post subject: |
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I've tried multiplying this values by four, but I get the same "bad magic number in superblock" error. |
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eccerr0r Watchman
Joined: 01 Jul 2004 Posts: 9679 Location: almost Mile High in the USA
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Posted: Fri Jul 26, 2013 8:54 pm Post subject: |
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I think the e2fsck is fine using the block numbers straight from mke2fs -n, but mounting requires the offset correction. Also what happens if you skew the block by one... and are you sure you made the filesystem initially with 4K blocks?
Did you check your dmesg log after trying to read the disk? Did the kernel report issues? It might have been a few bad sectors here and there, just want to make absolutely sure because reading a different partition doesn't mean the sectors in the partition you're having trouble with are still good. _________________ Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching? |
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temporary_user n00b
Joined: 26 Aug 2012 Posts: 37
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Posted: Thu Aug 15, 2013 5:25 pm Post subject: |
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Here's what happens when I try to mount it with Code: | mount -o ro,sb=131072 /dev/sda5 /mnt/gentoo
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Code: | [ 954.697516] REISERFS warning (device sda5): super-6502 reiserfs_getopt: unknown mount option "sb=131072"
[ 954.697831] reiser4[mount(3004)]: parse_options (fs/reiser4/init_super.c:253)[nikita-2307]:
WARNING: Unrecognized option: "sb=131072"
[ 954.698308] EXT3-fs (sda5): error: can't find ext3 filesystem on dev sda5.
[ 954.698879] EXT2-fs (sda5): error: can't find an ext2 filesystem on dev sda5.
[ 954.699444] EXT4-fs (sda5): VFS: Can't find ext4 filesystem
[ 954.699919] SQUASHFS error: Can't find a SQUASHFS superblock on sda5
[ 954.700261] FAT-fs (sda5): Unrecognized mount option "sb=131072" or missing value
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