Re: [gentoo-user] boot problems

["Canek Peláez Valdés" <caneko@gmail.com>]

On Fri, May 16, 2014 at 7:10 AM, Stefan G. Weichinger <lists@xunil.at> wrote:
> Am 16.05.2014 13:56, schrieb Bruce Schultz:
>
>>> I ask because in all my reorganizing furor I also thought that now
>>> with btrfs only I could get rid of "lvm mdraid" as dracut-modules.
>>> I can try ... ;-) (don't call me "ricer")
>>
>> If you have a multi-disk btrfs, I think you need to add the btrfs
>> dracut module. At least that's how I remember it, but its been a
>> while & my memory could be failing me, or it could well have changed
>> since then.
>
> I currently have in /etc/dracut.conf:
>
> add_dracutmodules+="bash systemd"
> hostonly="yes"
> hostonly_cmdline="yes"
>
> and am able to boot via grub2 and efi, that means,
>
> /boot/efi (vfat) on /dev/sda1 (sda is the SSD)
>
> and
>
> / as btrfs-subvol on /dev/sda2 (with /boot as directory on it).
>
> So no multi-disk btrfs for / or /boot on this machine.
>
> -
>
> removing "lvm mdraid" from dracut slimmed down the initrd from around
> 6.8 MB to 5.5 MB ... nice, but not necessary as Canek mentioned.
>
> I just "play" with it to learn and understand even better.
>
> I am not sure what the module "systemd" does or is good for, and
>
> https://www.kernel.org/pub/linux/utils/boot/dracut/dracut.html#dracut.kernel
>
> does look scary and didn't tell me more about that module yet.

With the systemd module, dracut uses systemd as init. So you have your
initramfs, which executes systemd to setup the machine up until /usr
is mounted, and then that instance of systemd calls the instance of
systemd in the hard drive.

If you don't use the systemd module, your initramfs uses a custom init
script to mount /usr and similar stuff. It seems to work, but I trust
more systemd to do it, and I certainly prefer not to rely on any
script during boot up.

Also, for non-trivial setups, I'm sure systemd handles them better
that a custom init script; that's why I recommended John to use the
systemd module.

Regards.
-- 
Canek Peláez Valdés
Profesor de asignatura, Facultad de Ciencias
Universidad Nacional Autónoma de México