Mdadm Boot Error, incrementally starting raid array Ubuntu SErver 14.04

bootmdadmraid

i build a small Server with Ubuntu 14.04 for Samba,
I has one SSD Drive (the ubuntu installation is on it)
and 2 3TB SATA Disk,
the sata disk are combined to a Raid 1 with mdadm.

Now sometimes (no everytime, i think it's maybe related to a dirty shutdown)
the system hangs at the boot process:

incrementally starting raid arrays
mdadm: Create user root not found 
mdadm: create group disk not found 
incrementally started raid arrays

these 4 lines keep repeating.
It's really strange cause the boot volume (the ssd) isn't configured as raid and this should not affect it?

Important edit: if i press ctrl + alt + del , the server reboots and starts up normaly,
if i look at the raid dev mdadm --detail /dev/md0
after the boot, everything looks good.

I'm not a linux pro and didn't find anything on the internet related to these errors, so now i'M a littel stuck, maybe somebody has a clue what the problem could be or some advanced troubleshooting advises (log files etc)?

thanks for reading
regards
Stefan

Best Answer

Had this as well. In my environment: 2x SAS HDDs configured as raid10.

The problem was that mpt2sas.ko was not loaded, and thus mdadm couldn't see any disk. This in turn was caused by a packaging error: when apt was removing unneeded wlan packages like crda, it also auto-removed the linux-image-extra-$VERSION package, which actually owns mpt2sas.ko.

To ensure, that the module gets loaded before the raid modules, I also did a

echo mpt2sas >>/etc/initramfs-tools/modules
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