[Ubuntu 14.04.1] initramfs try to mount /root before it is assembled

[Gilles DOFFE]

After forcing Ubuntu 14.04.1 to use mdadm instead of buggy dmraid for fakeraid imsm :
https://bugs.launchpad.net/ubuntu/+source/mdadm/+bug/1318351/comments/7

I have a new bug at startup that seems to be a race condition.
initramfs try to mount RAID1 array as /root before it is fully assembled, giving this kind of error :
mounting /dev/disk/by-uuid/267c4681-5574-42af-8dad-3f3483c08dba on /root failed: Device or Resource busy

After that, I have the initramfs rescue shell. If i try to mount the device by hand it works.
A workaround is to add a "sleep" in initramfs, which is quick and dirty but works.

Thanks to bobbus2 on ubuntu forum for that workaround :
http://ubuntuforums.org/showthread.php?t=2241430&p=13114328#post13114328

How to wait properly for RAID array to be assembled ?

$ mdadm --version
mdadm - v3.2.5 - 18th May 2012

$ uname -provism
Linux 3.13.0-40-generic #69-Ubuntu SMP Thu Nov 13 17:53:56 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

[Thomas (t.c)]

I hit exactly the same issure with Software RAID 1 and a fresh install from UEFI Ubuntu 14.04.1 Server amd64.