Merlin is no more. Merlin was my N40L-Microserver which performed its duty for twelve years. Yet suddenly it stopped working. Just would not boot up anymore.
I decided not to buy a new one, but I have to do someething to access the data, so I decided to buy a USB case for the four discs inside Merlin. Here is the disc-setup:
- Two 1 GB discs in a soft-raid level 1, with an lvm installed on the soft-raid. It was used to store the data.
- On 250 GB disc for operating system and so on. I never migrated to this to boot directly from the raid.
- On 2 GB disc for backups.
After installing discs in the case and connecting it to my laptop via USB, I ran
sudo mdadm --assemble --scan --verbose --force
to initialize the drives, so I could mount them and access the data.
The problem occured after disconnecting the discs (or better said: Disconnecting the Thunderbolt Dock that the discs are connected to.)
I got I/O errors after reconnecting.
I tried to unount the discs and shut down the raid, but a small piece was missing. I got the following error after doing
➜ ~ sudo mdadm --stop -f /dev/md0
mdadm: Cannot get exclusive access to /dev/md0:Perhaps a running process, mounted filesystem or active volume group?
Here is what worked, and this answer on StackExchange helped me with it.
# 1. Unmount and stop everything
sudo umount /media/merlin
sudo dmsetup remove main-root
sudo mdadm --stop /dev/md0
# 2. Restart
sudo mdadm --assemble --scan --verbose
If the does not work, there might be processes around using this device:
sudo lsof | grep md0
should only report something like this
md0_raid1 583 root cwd DIR 252,2 4096 2 /
md0_raid1 583 root rtd DIR 252,2 4096 2 /
md0_raid1 583 root txt unknown /proc/583/exe