On 3/14/2023 10:03 AM, Robert Heller wrote:
At Tue, 14 Mar 2023 09:50:33 -0400 Bowie Bailey <Bowie_Bailey@xxxxxxx>,? CentOS mailing list <centos@xxxxxxxxxx> wrote:
I know I will have to bring the drive online as a broken array, but I've
done that from other systems. The only question there is can I simply
rebuild it with a different name. I assume I can just do "mdadm -A
--run /dev/md0 /dev/sdc1" (possibly with "--force" due to the broken
array) even if sdc1 was originally part of the existing md127 array?
This should work.
Unfortunately, no. The system would not mount the drive without some
other changes. Listing the process here for anyone else who comes
across this thread.
Trying to start the array (with or without --force), fails with the message:
mdadm: Found some drive for an array that is already active: /dev/md127
mdadm: giving up
I found with some digging that I needed to change the UUID of the drive
to be able to mount it separately from the existing array. I used
"sgdisk -G /dev/sdg1" to do this. It worked, but gave quite a few scary
warning messages in the process. A better idea would have been to use
uuidgen to generate a random uuid and then start the array like this:
mdadm --assemble /dev/md99 --update=uuid --uuid=<newuuid> /dev/sdg1
(might require --force for a broken array, I'm not sure since I didn't
actually do it this way)
Once the array is running, there is another problem. Attempting to
mount the array gives another error:
mount: wrong fs type, bad option, bad superblock on /dev/md99,
missing codepage or helper program, or other error
Useless error message. You have to look in dmesg to see the actual problem:
XFS (md99): Filesystem has duplicate UUID
7e237dbd-6c24-4781-98d1-a1ae80a3ed13 - can't mount
I would assume you would have a similar issue with any other
filesystem. In my case, since it is XFS, I used uuidgen to generate
another random uuid and then updated it like this:
xfs_admin -U <newuuid> /dev/md99
After that, the filesystem mounted normally.
Hopefully that is helpful for anyone else who finds themselves in this
situation.
--
Bowie
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