January 31, 2016

Lab 17.1 - device file can be unpredictable

I did the lab 17.1 to set up a RAID system on my Ubuntu 15.04
I did as mentioned in the lab/solution. Though I defined the RAID device file to be /dev/md0 it turns out that after reboot the device file got renamed to /dev/md127 without notice.

I figured this out because my Ubuntu booted into emergency mode. I had put /dev/md0 in the /etc/fstab file according to lab instruction, but the boot failed because the device file was finally named /dev/md127 for some reason.

Does anyone have an explanation for that?

I wonder why the RAID device file got renamed to /dev/md127 when I defined it to be /dev/md0.

The only thing that I did differently from the lab instructions was that I did not create a file /etc/mdadm.conf. Instead my system already had a file /etc/mdadm/mdadm.conf so I simply added the line that got returned by the command
mdadm --detail --scan
That line was (it is really one line, but the web page might display it in more than one line):
ARRAY /dev/md0 metadata=1.2 name=elyasin-lcfs:0 UUID=4a491b9e:6590823a:c52acf39:8f9f5bb3

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