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Re: Debian machine not booting



James Allsopp wrote:
> One other point sda isn't the boot hard drive, that's the partitions /sdb1
> and sdc1, but these should be the same (I thought I'd mirrored them to be
> honest).

I don't see sda anywhere.  It might be a dual booting Windows disk?
Or other.  But the BIOS will boot the first disk from the BIOS boot
order.  BIOS boot order may be different from OS disk order.  It can
be confusing.  I might assume that BIOS sata0 is the same as the OS
disk sda but actually it often is different.  Let's ignore this for
now.

You have sdb1 and sdc1 mirrored into md1.  I can see that because the
UUID is identical.

> /dev/md1:
>         Version : 1.2
>   Creation Time : Thu Jan 31 22:43:49 2013
>      Raid Level : raid1
>      Array Size : 1953510841 (1863.01 GiB 2000.40 GB)
>   Used Dev Size : 1953510841 (1863.01 GiB 2000.40 GB)

>    Raid Devices : 2
>   Total Devices : 1
>     Persistence : Superblock is persistent
>
>     Update Time : Tue Jul  2 13:49:55 2013
>           State : clean, degraded
>  Active Devices : 1
> Working Devices : 1
>  Failed Devices : 0
>   Spare Devices : 0
>
>            Name : Hawaiian:1  (local to host Hawaiian)
>            UUID : a544829f:33778728:79870439:241c5c51
>          Events : 112
>
>
>     Number   Major   Minor   RaidDevice State
>        0       0        0        0      removed
>        1       8       65        1      active sync   /dev/sde1

That info is the same as:

> /dev/md127:
>         Version : 1.2
>   Creation Time : Thu Jan 31 22:43:49 2013
>      Raid Level : raid1
>      Array Size : 1953510841 (1863.01 GiB 2000.40 GB)
>   Used Dev Size : 1953510841 (1863.01 GiB 2000.40 GB)
>    Raid Devices : 2
>   Total Devices : 1
>     Persistence : Superblock is persistent
>
>     Update Time : Tue Jul  2 13:49:29 2013
>           State : clean, degraded
>  Active Devices : 1
> Working Devices : 1
>  Failed Devices : 0
>   Spare Devices : 0
>
>            Name : Hawaiian:1  (local to host Hawaiian)
>            UUID : a544829f:33778728:79870439:241c5c51
>          Events : 106
>
>
>     Number   Major   Minor   RaidDevice State
>        0       8       49        0      active sync   /dev/sdd1
>        1       0        0        1      removed

The UUIDs are identical.  Therefore those two disks are mirrors of
each other.  And note:

> /dev/md1: (/dev/sde1)
>     Update Time : Tue Jul  2 13:49:55 2013
> /dev/md127: (/dev/sdd1)
>     Update Time : Tue Jul  2 13:49:29 2013

sde1 is newer than sdd1.  This seems consistent with it being the best
copy to keep.  If it were the other way around I would think about
using the other one.  But selecting the right master is important
since it is a component of the lvm.

> How should I proceed from here?

I would proceed as previously suggested.  I would do this:

  mdadm --stop /dev/md127
  mdadm --manage /dev/md1 --add /dev/sdd1
  watch cat /proc/mdstat

That will discard the older stale copy of the mirror on sdd1.  It will
use sdd1 as a mirror of sde1.  After doing the add the mirror will
sync and you can watch the progress using 'watch cat /proc/mdstat'.
Use control-c to interrupt it when you want to stop it.

> For ruther information:
> /dev/sdb3:
> Preferred Minor : 126
> ...
> /dev/sdc3:
> Preferred Minor : 126
> ...

That further information looked _okay_ to me.  But I would still
change the md126 back to md0.

  mdadm --stop /dev/md126
  mdadm --assemble /dev/md0 --update=super-minor /dev/sdb1 /dev/sdc1
  cat /proc/mdstat

Since it is clean now it will be stopped cleanly and reassembled
cleanly and no sync will be needed.  The --update=super-minor will
reset the superblock with the updated md0 minor device number.

Then update /etc/mdadm/mdadm.conf and rebuild the initrd.

Bob

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