Re: dm-crypt over raid6 unreadable after crash

[Louis-David Mitterrand <vindex+lists-linux-raid@apartia.org>]

On Thu, Jul 07, 2011 at 08:41:36AM -0400, Phil Turmel wrote:
> 
> So, cryptsetup saw and properly handled /dev/md2.
> 
> [...]
> 
> Well.  /dev/md1 is assembled correctly as far as I can tell.  That
> make me wonder what else might be in play.  First, it would be good to
> know if the luks data is truly intact at the 1MB offset.  As a test,
> please add a linear device mapper layer that skips the 1MB.  Like so:
> 
> echo 0 1683724288 linear /dev/md1 2048 | dmsetup create mdtest

That worked fine.

I then successfully unlocked mdtest with:

	cryptsetup luksOpen /dev/mapper/mdtest cmd1

> Depending on grml's udev setup, this may prompt you to unlock
> /dev/mapper/mdtest.  Otherwise, use cryptsetup to test it, and then
> unlock it.  Do *NOT* mount yet.  Run "fsck -n" to see if it is intact.

root@grml /dev/mapper # xfs_check /dev/mapper/cmd1
xfs_check: /dev/mapper/cmd1 is not a valid XFS filesystem (unexpected SB magic number 0xd0f1b462)
xfs_check: size check failed
xfs_check: WARNING - filesystem uses v1 dirs,limited functionality provided.
xfs_check: read failed: Invalid argument
xfs_check: data size check failed
cache_node_purge: refcount was 1, not zero (node=0x1835a30)
xfs_check: cannot read root inode (22)
cache_node_purge: refcount was 1, not zero (node=0x1835c80)
xfs_check: cannot read realtime bitmap inode (22)
xfs_check: size check failed
xfs_check: WARNING - filesystem uses v1 dirs,limited functionality provided.
xfs_check: read failed: Invalid argument
xfs_check: data size check failed
bad superblock magic number d0f1b462, giving up

> I also wonder if the md device itself was partitioned, maybe with EFI
> GPT, and the grml liveCD doesn't support it?  (Long shot.)  Please
> show "zcat /proc/config.gz |grep PART"

root@grml /dev/mapper # zcat /proc/config.gz |grep PART
CONFIG_PM_STD_PARTITION=""
CONFIG_MTD_PARTITIONS=y
CONFIG_MTD_REDBOOT_PARTS=m
# CONFIG_MTD_REDBOOT_PARTS_UNALLOCATED is not set
# CONFIG_MTD_REDBOOT_PARTS_READONLY is not set
CONFIG_MTD_AR7_PARTS=m
CONFIG_PARTITION_ADVANCED=y
CONFIG_ACORN_PARTITION=y
# CONFIG_ACORN_PARTITION_CUMANA is not set
# CONFIG_ACORN_PARTITION_EESOX is not set
CONFIG_ACORN_PARTITION_ICS=y
# CONFIG_ACORN_PARTITION_ADFS is not set
# CONFIG_ACORN_PARTITION_POWERTEC is not set
# CONFIG_ACORN_PARTITION_RISCIX is not set
CONFIG_OSF_PARTITION=y
CONFIG_AMIGA_PARTITION=y
CONFIG_ATARI_PARTITION=y
CONFIG_MAC_PARTITION=y
CONFIG_MSDOS_PARTITION=y
CONFIG_MINIX_SUBPARTITION=y
CONFIG_SOLARIS_X86_PARTITION=y
CONFIG_LDM_PARTITION=y
CONFIG_SGI_PARTITION=y
CONFIG_ULTRIX_PARTITION=y
CONFIG_SUN_PARTITION=y
CONFIG_KARMA_PARTITION=y
CONFIG_EFI_PARTITION=y
CONFIG_SYSV68_PARTITION=y

> I'm running out of ideas.

Well thanks a lot for trying at least. At least now I understand how
'linear' can be used.