[arch-general] mkinitcpio: mdadm_udev Hook

[Dave Reisner]

> On 03/10/12, Thomas B?chler wrote:
> 
>> You need to create a file /etc/mdadm.conf. mdadm --examine --scan will
>> generate the right lines for you. This file will be added to the
>> initramfs and your names will be fine again.
> 
> Yep, that's what I've done, and I've used the mdadm hook as I have in
> the
> past.
> 
> Based on the mkinitcpio wiki page, and the forum post, I'm under the
> impression that using mdadm_udev to auto-assemble the arrays is what I
> should be using (and is what will be supported in the future).
> 
> The mdadm_udev hook does work as advertised, but I don't see how I can
> use it when I need a known /dev/mdx device for use in something like a
> "cryptdevice=" kernel arg.

Thomas is pointing out that the mdadm_udev hook will (should?) still
honor your /etc/mdadm.conf if it has ARRAY decls in it (you'll see it
being picked up on the mkinitcpio run if this is true). If that isn't
happening, or it isn't being honored, we should find out why.

Alternatively, cryptdevice understands tags, e.g:

  cryptdevice=UUID=46c78135-8ac0-4928-8b26-5d23a77b1ff1:cryptrewt

Of course, since there isn't a filesystem involved, UUID is the only one
that makes sense for MBR disks. PARTUUID is also supported, and
PARTLABEL support will be available in the next mkinitcpio release.

Cheers,
Dave