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mdadm - change /dev/md122 to /dev/md3
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Sum1
Tux's lil' helper
Tux's lil' helper


Joined: 26 Dec 2006
Posts: 101

PostPosted: Tue Feb 19, 2013 1:01 pm    Post subject: mdadm - change /dev/md122 to /dev/md3 Reply with quote

Hello,

Not really an installation, but a kernel re-compile and kernel panic upon re-boot.
I chrooted from minimal install iso on usb device and recompiled kernel.
In the chroot environment, cat /proc/mdstat shows all my raid partitions as /dev/md122 - /dev/md127 instead of what my fstab indicates: /dev/md0 through /dev/md6.

I didn't think there was a problem because I was able to compile kernel and access all data on partitions.
Now, upon new kernel install, the boot states:

md6 (driver?)
md5 (driver?)
md4 (driver?)
md122 (driver?)
md2 (driver?)
md123 (driver?)

Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block (2,0).

It appears md122 is what my /etc/fstab knows as /dev/md0 root partition and /dev/md123 is the /dev/md1.
I didn't change anything in my grub.conf or fstab.
How do I make mdadm properly read/report the raid partitions as they are in /etc/fstab upon reboot.

Thank you for your help.
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frostschutz
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Joined: 22 Feb 2005
Posts: 2441
Location: Germany

PostPosted: Tue Feb 19, 2013 3:34 pm    Post subject: Reply with quote

The metadata stores hostnames and super-minor number. You can update these on assemble, see man mdadm on --update.

However probably more important is what your /etc/mdadm.conf says about your RAID arrays. They should be specified by UUID there and given a /dev/mdX device name to be used on assembly. mdadm will use mdadm.conf to build the arrays whenever possible and only fall back to alternate methods such as when scanning and assembling RAIDs in a live/rescue system.
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Sum1
Tux's lil' helper
Tux's lil' helper


Joined: 26 Dec 2006
Posts: 101

PostPosted: Tue Feb 19, 2013 9:39 pm    Post subject: Reply with quote

frostschutz wrote:
The metadata stores hostnames and super-minor number. You can update these on assemble, see man mdadm on --update.

However probably more important is what your /etc/mdadm.conf says about your RAID arrays. They should be specified by UUID there and given a /dev/mdX device name to be used on assembly. mdadm will use mdadm.conf to build the arrays whenever possible and only fall back to alternate methods such as when scanning and assembling RAIDs in a live/rescue system.


Thanks for your reply, Frostschutz.
I see part of the trouble may be that my mdadm.conf is entirely commented out by #'s.
I should have provided parameters in there a long time ago.

I'll definitely look more closely on the mdadm --update capabilities.
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Sum1
Tux's lil' helper
Tux's lil' helper


Joined: 26 Dec 2006
Posts: 101

PostPosted: Tue Feb 19, 2013 9:58 pm    Post subject: Reply with quote

Probably a dumb question, but better safe than sorry --

Should any/all mdadm commands on partitions be performed with them unmounted and not while chrooted?

I see that I could do: mdadm -A --name=/dev/md3 /dev/sda3 /dev/sdb3
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