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We're running a small server over here on a raspberry pi, debian jessie, to host both our owncloud and - more important - our repo and build server.

To be sure that data will not get corrupted, I have set up a software raid, spanning across two USB drives.

After trying to rename the machine, and obviously, after the first reboot after setting up the MD, I am not able to get it back up and running:

root@pi3:~# cat /proc/mdstat
Personalities :
unused devices: <none>


root@pi3:~# mdadm --examine --brief --scan
ARRAY /dev/md/0  metadata=1.2 UUID=125e3855:8c3326a2:dd067877:60d35ba7 name=pi3:0

root@pi3:~# ls /dev/md0
ls: cannot access /dev/md0: No such file or directory

root@pi3:~# fdisk -l | grep Linux
/dev/mmcblk0p2      137216 61962239 61825024 29.5G 83 Linux
/dev/sda1        2048 1953523711 1953521664 931.5G fd Linux raid autodetect
/dev/sdb1        2048 1953523711 1953521664 931.5G fd Linux raid autodetect
/dev/sdc2       41945088 312581807 270636720 129.1G 83 Linux

From what I understood so far, the mdadm should be able to provide the array - after all the devices are there and can be detected.

However, I cannot mount /dev/md0 anymore because there are no personalities detected.

Is there anybody who can point me to the next steps? Googling for an empty personalities line is not so successful and the personalities line does not contain a catchy keyword...

  • Does /dev/md/0 exist ? Can you post your etc/mdadm.conf file ? Have you tried mdadm --add /dev/md0 /dev/sda1 ; mdadm --add /dev/md0 /dev/sdb1 ? – davidgo Dec 31 '16 at 20:36
  • @davidgo pi@pi3:~ $ cat /etc/mdadm/mdadm.conf | grep -v ^# CREATE owner=root group=disk mode=0660 auto=yes HOMEHOST <system> MAILADDR root – M.Schnick Jan 1 '17 at 16:52
  • even after including the output of mdadm --examine --brief --scan to the mdadm.conf and rebooting, the situation did not get any better. /dev/md is an empty directory. root@pi3:~# ls -ld /dev/md/ drwxr-xr-x 2 root root 40 Dec 31 16:54 /dev/md/ – M.Schnick Jan 1 '17 at 16:56
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after doing the following steps, things are running fine now:

root@pi3:~# mdadm --examine --scan >> /etc/mdadm/mdadm.conf
root@pi3:~# mdadm --assemble /dev/md/0

I had to modify the fstab to contain Code:

/dev/md/0       /mnt/raid       ext4    defaults        0       0

Now things are running fine, again.

At least for the time being, another reboot will tell if persistence is also given!

Many thanks,

Michael

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