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

[wraeth@wraeth.id.au]

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On Tue, Nov 11, 2014 at 09:56:09PM +0100, Michael Mair-Keimberger wrote:
> Today I've started to play around with systemd but so far I couldn't get
> it to boot. I've followed the how to from the gentoo wiki [1], but I
> stuck somehow.

I found systemd to be rather tricky to implement on some of my systems,
but this was a while ago and was in a more complex configuration that
you're using (though as most people are suggesting, I used dracut to
generate my initrd).

I would also suggest to use either dracut or genkernel-next to generate
an initramfs if you wanted to go down that path. Note that
sys-kernel/genkernel (as opposed to sys-kernel/genkernel-next) can have
issues with systemd (the last time I tried it it complained about
systemd and suggested using genkernel-next).

If you would prefer a hand-rolled one, I can't offer much, but as I
think has already been suggested, one key point is to call the correct
binary.

The systemd binary itself is /usr/lib/systemd/systemd, though calling
/sbin/init may work if that's configured in such a way as to launch
systemd.

The other point I might add is that my system, which uses dracut, has
systemd launched with some specific arguments:

  ps -fp 1
  UID        PID  PPID  C STIME TTY          TIME CMD
  root         1     0  0 11:31 ?        00:00:00
  /usr/lib/systemd/systemd --switched-root --system --deserialize 18

This may be relevant when creating your own initramfs.

> First of all, with systemd installed I can't install lvm2 with the
> static use flag anymore, which is mandatory for being able using it for
> a initramfs. Why isn't that possible? How can I use the lvm binaries for
> my initramfs?

Again, as I think has been mentioned, the 'static' use flag is typically
a shortcut for easily building an initrd. Provided you include all the
dependencies of a given binary (as seen with `ldd /path/to/binary`) you
don't need static binaries.

> This lead me to my second question. At the wiki, the only way to create
> an initramfs for systemd was with genkernel (genkernel --udev --lvm).
> While the command itself is pretty useless (it's `genkernel --udev --lvm
> initramfs` if you want to create the initramfs -> is this a bug??) i
> also would like to use my own initramfs.

I'm not sure what you mean by the command is useless and is a bug.
Genkernel has multiple potential targets - 'all' for building the kernel
and initrams, 'kernel' for the kernel binary and modules, 'initramfs'
for just the initramfs image, etc. This command should generate an
initramfs with the required components for systemd, udev and lvm.

Hopefully some of this will help clear things up a little.

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

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