Re: [gentoo-user] difficulties with lvm2+systemd+grub2

[wraeth <wraeth@wraeth.id.au>]

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On Fri, Nov 14, 2014 at 07:43:18PM +0100, Michael Mair-Keimberger wrote:
> Basically my changes in my grub config were already correct, however I
> completely forgot, that, since I wrote my own init script, arg's like
> "root" and "init" simply weren't used by my script...
> If you look at my script, I only check the cmdline for "lvm", so
> setting "init" or "root" haven't any effect at all :D

Glad you got this part of it sorted! I know how both relieving and
frustrating it can be to find such a simple thing as the solution - it
took me two weeks to realise I was calling 'mpc' and not 'mpd' in my
startup script, explaining why MPD was never running... :-/

> Regarding dracut: Even though I got it to work, it also just bootet
> openrc and not systemd. Don't know why and I didn't digged further after
> it worked with my own script.

You could try inspecting dmesg to try and determine why it isn't loading
your chosen init. It could be something as simple as a typo, or if the
filesystem (if you have /usr on a separate partition) isn't available at
the time it's trying to launch init.

> Regarding LVM:
> As mentioned systemd can't mount my lvm partitions from fstab. Those lvm
> partitions should be mounted by UUID, but it seems like systemd can't
> find them, even though there are available afterwards (under
> /dev/vg0/...).

I've found dracut initrd's can be a little finicky with LVM volumes.
With that in mind, here's the kernel cmdline for one of my systems wich
uses LUKS->LVM->EXT4 for it's root partition. Note that it has explicit
arguments for *all* LV's and not just root.

  BOOT_IMAGE=/vmlinuz-3.17.1-gentoo-r1 root=/dev/mapper/vg1-root ro
  rd.luks.uuid=luks-3f93b8aa-cf8b-4312-85d6-d45cffa59780
  rd.lvm.lv=vg1/swap rd.lvm.lv=vg1/root resume=/dev/mapper/vg1-swap
  rootflags=rw,noatime,data=ordered rootfstype=ext4 quiet

> If I comment them out in /etc/fstab (they are not important) systemd
> boots just fine. I've also set "use_lvmetad = 1" in /etc/lvm/lvm.conf as
> mentioned at the systemd wiki.

This is a dracut-ism, in that if a static filesystem (as denoted by it's
presence in /etc/fstab) is unmountable, it will assume there are
problems and will drop to recovery. The idea of recovery is to identify
your root partition with a symlink to the device node, after which you
*should* be able to continue.

  ln -s /dev/<root_device> /dev/root

See [1] for more. That being said, it may continue to drop to recovery -
I've found the dracut recovery console to be a little temperamental with
things like that...

[1]: http://fedoraproject.org/wiki/How_to_debug_Dracut_problems

Cheers;
-- 
wraeth <wraeth@wraeth.id.au>
GnuPG Key: B2D9F759

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