[PLUG] Need mdadm help

John Jason Jordan johnxj at comcast.net
Tue Dec 28 04:20:02 UTC 2010


On Mon, 27 Dec 2010 19:24:47 -0800
John Jason Jordan <johnxj at comcast.net> dijo:

>>Well, mdadm --query fails because I didn't specify a device. Of
>>course, that is the whole problem. 
>
>The correct command is "cat /proc/mdstat," since the arrays are
>maintained in mdstat, which is just a text file. 
>
>Turns out my arrays are named md0 to md3, and the query command goes
>"mdadm --query /dev/md0" etc., although --detail gives better results.
>And it appears that md1 is the bad one. 
>
>The md1 array is composed of /dev/sda1 and /dev/sdb1, but the --detail
>command says that /dev/sda1 has been removed. 
>
>I'm trying to get my head around why removing /dev/sda1 would give me
>the symptoms I am having. The only problem is that each dist-upgrade
>installs a new kernel option in the Grub menu, but I cannot boot to
>anything but the last Hardy kernel. Selecting any of the newer kernels
>gives me a Grub error -15. So what did these dist-upgrades do, write a
>kernel to a non-existent disk?

It's trivially easy once you figure out how. All had to do was:

mdadm /dev/md1 -a /dev/sda1 # the -a means "add"

It took half an hour to rebuild the array. When I rebooted I could boot
into the new kernels without a Grub error -15. 

I still don't understand exactly why. But it's fixed. I think.

And it's currently dist-upgrading to Lucid. Later I'll disassemble the
arrays. But that's an exercise for another day.



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