[Bug 823499] Re: mdadm failed to autocreate md /dev entries

[m0sia]

It seems i found the root cause of the initial problem: there were a
pair of raid superblocks on each hard drive(ex in both /dev/sdb and
/dev/sdb1). Until 11.04 it somehow worked for me.

Now i've removed the unnecessary raid superblocks and everything works.
sudo mdadm --zero-superblock /dev/sdb
sudo mdadm --zero-superblock /dev/sdc

But i still wonder if it is a bug or a feature.

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Title:
  mdadm failed to autocreate md /dev entries

Status in “mdadm” package in Ubuntu:
  New

Bug description:
  I've just upgraded from 10.11 to 11.04

  I have the following mdadm.conf(worked like a charm for 10.11):

  DEVICE partitions

  CREATE owner=root group=disk mode=0660 auto=yes

  HOMEHOST <system>

  MAILADDR root

  ARRAY /dev/md0 level=raid1 num-devices=2
  UUID=78bab575:75f15162:d7535677:b830ce1f

  After upgrade i have the following mdstat:

  $ cat /proc/mdstat 
  Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
  md0 : inactive md127p1[0](S)
        488383936 blocks
         
  md127 : active (auto-read-only) raid1 sdc[1] sdb[0]
        488386496 blocks [2/2] [UU]
        	resync=PENDING
        
  unused devices: <none>

  Two get my raid1 up and running i have to do the following:

   $sudo mdadm --stop /dev/md0
   $sudo mdadm --stop /dev/md127
   $sudo mdadm --assemble /dev/md0 /dev/sdb1 /dev/sdc1
   $sudo mount /dev/md0 /mnt/raid 

  
  cat /proc/mdstat 
  Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
  md0 : active raid1 sdb1[0] sdc1[1]
        488383936 blocks [2/2] [UU]
        
  unused devices: <none>

  $ sudo mdadm --detail --scan --verbose
  ARRAY /dev/md0 level=raid1 num-devices=2 metadata=0.90 UUID=78bab575:75f15162:d7535677:b830ce1f
     devices=/dev/sdb1,/dev/sdc1

  How can I get mdadm autodetection work as expected?

  Best regards,
  Dmitry

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