Given a single raid1 drive in degraded/rebuilding state, can it be force mounted?  I'd like to recover all the files before undertaking the dangerous operation of pairing it and rebuilding.  As far as I can tell the drive is in perfectly good shape, fully intact. The pair drive is partly failed.If the drive was not in rebuilding state I'd know exactly what to do. Here is what I have tried:# mdadm --verbose --assemble /dev/md8 /dev/sdb1  --forcemdadm: looking for devices for /dev/md8mdadm: /dev/sdb1 is identified as a member of /dev/md8, slot 1.mdadm: no uptodate device for slot 0 of /dev/md8mdadm: added /dev/sdb1 to /dev/md8 as 1mdadm: /dev/md8 assembled from 0 drives and  1 rebuilding - not enough to start the array.# cat /proc/mdstat                       md8 : inactive sdb1[1](S)      976759808 blocks super 1.2          md0 : active raid1 sdc1[0]      976759672 blocks super 1.2 [2/1] [U_]# mdadm --stop /dev/md8mdadm: stopped /dev/md8# mount /dev/sdb1 /mnt/temp2mount: unknown filesystem type 'linux_raid_member'# mount -o ro -t ext3 -b 2048 /dev/sdb1 /mnt/temp1mount: wrong fs type, bad option, bad superblock on /dev/sdb1.# foremost -i /dev/sdb -o /tmp/foo    (this results in perfectly good files)In this particular case the foremost command recovers files, so something is definitely on the drive, if I could only get the superblock offset correct.And in this particular case assembling both halves of the array crashes the kernel(!), so that's not a real option anyway (aside from the safety issues).UPDATE: added output of mdadm# mdadm --examine /dev/sdb1/dev/sdb1:          Magic : a92b4efc        Version : 1.2    Feature Map : 0x2     Array UUID : e00a291e:016bbe47:09526c90:3be48df3           Name : ubuntu:0  Creation Time : Wed May 11 12:26:39 2011     Raid Level : raid1   Raid Devices : 2 Avail Dev Size : 1953519616 (931.51 GiB 1000.20 GB)     Array Size : 1953519344 (931.51 GiB 1000.20 GB)  Used Dev Size : 1953519344 (931.51 GiB 1000.20 GB)    Data Offset : 2048 sectors   Super Offset : 8 sectorsRecovery Offset : 0 sectors          State : clean    Device UUID : 41346f44:ccacbbf7:0c17c133:eb7b341f    Update Time : Sat Apr 13 00:02:08 2013       Checksum : 483a0a44 - correct         Events : 402833   Device Role : Active device 1   Array State : AA ('A' == active, '.' == missing)
How do I recover files from a single degraded mdadm raid1 drive? not enough to start the array
data recovery;software raid;mdadm
If it's RAID 1, and if you know the data offset (e.g. 2048 sectors, you can usually find out the exact data offset by mdadm --examine /dev/sdb1), then you can create a read-only (to be safe) loop device like so:# losetup --find --show --read-only --offset $((2048*512)) /dev/sdb1/dev/loop7And then try to check then mount the printed loop device:# fsck.ext3 -n -v /dev/loop7# mount -o ro /dev/loop7 /mnt/recoverymount might be able do this directly with the -o ro,loop,offset= options, but I prefer to create the loop device manually, just to make sure it's really read-only.If the filesystem itself is damaged, you should make an image using dd, and run experiments such as fsck on the image. Alternatively you can use Linux network block device to put a copy-on-write layer on top of the disk, so you can fsck that layer without actually writing anything onto the disk itself (nbd-server -c/nbd-client, will create a /dev/nbdX device for you to play with). It might be possible to do the same with device mapper - but I've never tried it.