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I have a mdadm software RAID6 that comes up inactive upon each reboot. All its disk are present but shown as spares. How do I make it start operational (active)?

This is it's state after reboot:

cat /proc/mdstat 
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
md0 : inactive sdg[2](S) sdf[1](S) sde[3](S) sdc[5](S) sdb[0](S) sda[4](S)
      xxxxxx blocks
unused devices: <none>

again here

sudo  mdadm --detail --scan           
INACTIVE-ARRAY /dev/md0 metadata=0.90 UUID=xxx

it is not possible just to assemble it, even with --force

sudo mdadm --assemble --scan --verbose
mdadm: looking for devices for /dev/md0
mdadm: /dev/sdg is busy - skipping
mdadm: /dev/sdf is busy - skipping
mdadm: /dev/sde is busy - skipping
mdadm: /dev/sdc is busy - skipping
mdadm: /dev/sdb is busy - skipping
mdadm: /dev/sda is busy - skipping

sudo mdadm --assemble --scan --force --verbose
mdadm: looking for devices for /dev/md0
mdadm: /dev/sdg is busy - skipping
mdadm: /dev/sdf is busy - skipping
mdadm: /dev/sde is busy - skipping
mdadm: /dev/sdc is busy - skipping
mdadm: /dev/sdb is busy - skipping
mdadm: /dev/sda is busy - skipping

But it can be manually assembled after I stop it:

sudo mdadm --manage --stop /dev/md0
mdadm: stopped /dev/md0
sudo mdadm --assemble --scan
mdadm: /dev/md0 has been started with 6 drives.
sudo  mdadm --detail --scan
ARRAY /dev/md0 metadata=0.90 bitmap=/media/intent.bin UUID=xxx

I'm on Ubuntu 18.04.1 LTS

4.15.0-36-generic #39-Ubuntu SMP Mon Sep 24 16:19:09 UTC 2018 x86_64 GNU/Linux

mdadm - v4.1-rc1 - 2018-03-22

What I have noticed is that 

sudo mdadm --examine /dev/sd[abcefg]

shows /dev/sde missing in the list below. (Only /dev/sde missing in that table for all disks/devices)

      Number   Major   Minor   RaidDevice State
this     3       8      112        3      active sync

   0     0       8       48        0      active sync   /dev/sdd
   1     1       8        0        1      active sync   /dev/sda
   2     2       8       16        2      active sync   /dev/sdb
   3     3       8      112        3      active sync
   4     4       8       32        4      active sync   /dev/sdc
   5     5       8       80        5      active sync   /dev/sdf
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1 Answer 1

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The culprit was the bitmap=/media/intent.bin statement in /etc/mdadm/mdadm.conf After I have just letft ARRAY /dev/md0 UUID=xxx there, the array started active after the reboot. (However now I have a problem that it doesn't use the external bitmap as it should.)

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  • 1
    Is /media/intent.bin available at the time the system tries to start the array?
    – Chris Davies
    Oct 14, 2018 at 7:13
  • Thanks @roaima this is exactly what happened. I have opened another question about that issue: askubuntu.com/questions/1083596/…
    – Diego
    Oct 14, 2018 at 12:59
  • Oh ok. Please remember to accept your own answer here (when you can).
    – Chris Davies
    Oct 14, 2018 at 13:12

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