[arch-dev-public] mdadm udev + initramfs (WAS: Re: Big changes to LVM2 in testing)

[Dave Reisner]

On Sun, Nov 04, 2012 at 05:07:59PM +0100, Thomas Bächler wrote:
> Am 03.11.2012 02:40, schrieb Eric Bélanger:
> > If you use both RAID and LVM, make sure that you use the mdadm_udev
> > hook instead of the mdadm one. I had to do this change to make my
> > system boot with the lvm2 package in [testing].
> 
> Okay, we figured this out by now:
> 
> The 'mdadm' hook does not only disable the auto-assembly, it lacks any
> udev rules in initramfs - this means that udev will not know about file
> system type on the RAID contents and LVM auto-assembly fails.

I guess I knew this, as it caused problems in the past when we created
mdadm_udev:

https://bugs.archlinux.org/task/28067

> The solution would be to include the udev rules in the mdadm hook as
> well, and just disable auto-assembly.

This was always the sticking point -- is there a way to disable auto
assembly but keep the rule file as is? I'd rather we didn't duplicate
it.

> On another note: The mdadm_udev behaviour used to be the default for a
> while, but we had a lot of whining about it - none of the affected
> people had any interest in figuring out why auto-assembly failed for
> them. I'd really like to get rid of the non-udev based mdadm assembly,
> so if anyone has an idea why there were problems, feel free to share.
> 
> While we're at it, I'd like to fix mdadm's udev rule to use
> BUILTIN+="blkid" instead of manually calling blkid.

This is definitely needed. I think the -o udev output from blkid is
going away in u-l 2.23. The blkid builtin is already almost a year old
-- would make more sense to just convince upstream to make the change.

d