[TriLUG] mdadm: no devices found for /dev/md0

T. Bryan tbryan at python.net
Wed Nov 29 19:51:27 EST 2006


On Tuesday 28 November 2006 08:53, T. Bryan wrote:

> After recent upgrades, my RAID1 device does not seem to be coming up during
> the boot process any more.

Some progress!  I think that the problem may be that I once created a RAID on 
these devices incorrectly.  I later reconfigured my RAID, but I think that 
the boot sequence is now detecting the old RAID set.  I could use some help 
from another RAID user out there.

If you have a RAID1 between /dev/hda1 and /dev/hdc1, for example, what do the 
following 4 commands return?

mdadm --examine /dev/hda | grep UUID
mdadm --examine /dev/hda1 | grep UUID
mdadm --examine /dev/hdc | grep UUID
mdadm --examine /dev/hdc1 | grep UUID

I'm hoping that the command on /dev/hda and /dev/hdc will tell you that there 
is no md superblock.  :)

On my machine, I should have a RAID1 between /dev/hde1 and /dev/hdg1, but I'm 
showing an md superblock on /dev/hde and /dev/hdg, too.  I don't think that's 
normal, but I'd like to confirm that with anyone else who's running a RAID.

I'll have to look at my notes, but I think that I once tried to create a RAID 
directly on the unpartitioned devices.  When I finally set up the RAID, I 
partitioned the devices and created the RAID across the partitions, not the 
raw devices.  But now, when my system boots up, it's bringing up the RAID on 
/dev/hde and /dev/hdg and not on /dev/hde1 and /dev/hdg1.  Worse, it looks 
like udev isn't recognizing /dev/hde1 and /dev/hdg1 because it has decided 
that /dev/hde and /dev/hdg are completely dedicated to a RAID.  

Anyway, I think that I might just need to run 

mdadm --zero-superblock /dev/hde
mdadm --zero-superblock /dev/hdg

and reboot.  I just don't want to do that until I'm a little more certain that 
the md superblock isn't supposed to be there.

Thanks,
---Tom




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