On Tue, Sep 4, 2012 at 2:45 PM, Ross Boylan <r...@biostat.ucsf.edu> wrote: > > Summary > > mdadm on squeeze rewrites the UUID I give it with the localhost, even > if I do not specify localhost. I am trying to repair a RAID for use > on lenny with an existing UUID. Is there a way to avoid the rewrite? > > Details > > A lenny host has two virtual machines, VM1 (lenny) and VM2 (squeeze). > There are two virtual disks, VD0 and VD1, whose 3rd partition forms > RAID1 (md1), intended for VM1. That same partition was in a RAID > before, but I grew it and so there is no RAID superblock near the end > anymore. I need to recreate the superblock without zapping the good data > on the partition. > > From VM2: > # mdadm --create /dev/md1 --uuid=6f05ff4e:b4d49c1f:7fa21d88:ad0c50a9 > --metadata=0.90 --level=mirror --raid-devices=2 /dev/sdb3 missing > mdadm: array /dev/md1 started. > # mdadm --examine /dev/sdb3 > /dev/sdb3: > Magic : a92b4efc > Version : 0.90.00 > UUID : 6f05ff4e:b4d49c1f:f1c4dd81:d9ca9b38 (local to host > squeeze00) > > The man appears to say the UUID specified on the command line should > govern(*), but it doesn't. > > Some possible fixes: > > 1) Get mdadm to use the UUID I specify. > > 2) Use the new UUID and edit the mdadm.conf for VM1 to match. Do I need > to update the initramfs, and if so how? And will VM1 accept the new > UUID, or do its own rewriting with its own hostname? > > 3) Use mdadm from the (lenny) host system, since the localhost stuff is > new in squeeze. I don't know how to access the virtual disks outside of > a VM to do this. > > 4) Find an appropriate rescue system image for lenny, start it in a VM, > and run mdadm from there. I wonder if stopping VM1's startup while it's > still in the initrd would be enough. > > (*) from man mdadm on squeeze: > > Also, using --uuid= when creating a v0.90 array will silently > override any --homehost= setting. > > Technically I didn't specify --homehost; maybe I should try that in > order to get the host ignored!
1) "I do not specify localhost" and "since the localhost stuff": you must mean "homehost". 2) Once you recreate the metadata and update "mdadm.conf", run "update-initramfs -u -k $(uname -r)" will update the initrd of the current kernel using the hooks in "/usr/share/initramfs-tools/hooks/mdadm". 3) I've never had to recreate the metadata of a running mdraid array but I'm curious as to whether it's possible without being booted from an initramfs or a live CD and runnning "mdadm --create ..." from there. 4) For metadata v0.9, the hostname's hashed and included in the UUID. The "homehost" corresponds to the "HOMEHOST" value in "mdadm.conf" and it's "<system>" by default (which points to the hostname of the system); unless you override it with "--homehost=..." when running "mdadm --create ...". I have no idea how passing both "--uuid" and "--homehost" when creating/assembling a v0.9 array will turn out, sorry. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/CAOdo=szmo1upmsbrpv1o5ve4c0euj9j-3jufwqm8bvjsaye...@mail.gmail.com
