Bug#737132: Regression: wheezy initrd loads md raids only if defined on mdadm.conf even with INITRDSTART='all'

[Michael Tokarev]

30.01.2014 17:45, Fabio Fantoni wrote:
> Package: mdadm
> Version: 3.2.5-5
> Severity: normal
> 
> I'm attempting to restore a backup of a root partition on a set of brand new disks (md raid1).
> On Wheezy, initramfs doesn't show md devices if they are not defined in /etc/mdadm/mdadm.conf even if on /etc/default/mdadm there is INITRDSTART='all'.
> Such problem may be caused by a regression (squeezy or wheezy) because on lenny I've been always did such task without problem.
[]
> Personalities : [raid1] 
> md1 : active raid1 sda3[0] sdb3[1]
>       72610624 blocks super 1.2 [2/2] [UU]

With 1.x superblock, the term "all" actually refers to all arrays belonging to this host,
which has current hostname recorded in the superblock (1.x format superblock has a place
for "homehost" field, while 0.90 format didn't have this field).

Previously, mdadm really tried to assemble any arrays found, but this turned out to be
wrong.  For example, when you insert hard drives from another system for recovery of
broken raid/filesystem, mdadm should NOT assemble arrays from there by default, because
this way we've a high risk of breaking stuff further.

Please ensure that you have the right homehost in your raid arrays (mdadm -D will tell you),
and -- the second part of the picture -- that this hostname is set correctly inside initrd
when mdadm is run.

Please note also that modern mdadm will try to check homehost even for 0.90 superblocks,
by doing some magic with the array UUID.  If your arrays were created by sufficiently
recent mdadm, the UUID has some bits of homehost mixed in.

Thanks,

/mjt