Cannot boot a fresh install with grub2 root fs on lvm

hokiau · n00b Joined: 24 Dec 2013 Posts: 18

[glsa=][/glsa]I read that grub2 could boot a system with / on a lvm volume. I did just that with a fresh install of gentoo with gpt, grub2, systemd. / is on /dev/vg/slash and /boot on a non-lvm partition. I generated the kernel with genkernel-next using --lvm and --udev params. grub2-mkconfig generated the grub2 configuration file with the "dolvm" kernel param. When I tried to boot the system, it said "Activating Logical Volume Groups", and then "/run/lvm/lvmetad.socket: connect failed: No such file or directory", and "/dev/mapper/vg-slash is an invalid root device..."

How do I make sure lvmetad.socket is there during boot?

szatox · Advocate Joined: 27 Aug 2013 Posts: 3135

If you have initramfs, any bootloader will boot linux on lvm.
Bootloader's job is to load kernel into RAM, optionaly load initramfs and then give up control.

However, AFAIR genkernel puts /etc/lvm/lvm.conf into initramfs, which means you must have lvm already configured by the time you build initramfs.

Also, it seems gentoo doesn't want to run without
root=/dev/ram0
(and real_root=<path to lvm volume>)

hokiau · n00b Joined: 24 Dec 2013 Posts: 18

Here's what I did:
1. in /etc/defaults/grub added GRUB_DEVICE=/dev/ram0, and added a kernel param "real_root=/dev/vg/slash"
2. grub2-mkconfig -o /boot/grub/grub.cfg
3. genkernel --lvm --udev all

Supposedly I should have the proper lvm params for initramfs. When I rebooted, I still saw the error:
/run/lvm/lvmetad.socket: connect failed: No such file or directory
...
/dev/vg/slash is an invalid root device

So, it's still not finding /run/lvm/lvmetad.socket. What is wrong?

webknjaz · n00b Joined: 29 Oct 2014 Posts: 8

Hi,

Did you manage to fix the issue?

Roman_Gruber · Posted: Wed Oct 29, 2014 2:20 pm Post subject:

well topic covers systemd

usually 512mb boot with ext2, initramfs from genkernel with proper kernel and openrc / eudev works quite well.

hokiau · n00b Joined: 24 Dec 2013 Posts: 18

i figured it out:
1. you need to genkernel with the --lvm flag.
2. make sure grub preload the lvm module. in /etc/default/grub add a line GRUB_PRELOAD_MODULES=lvm.
3. boot kernel with dolvm parameter. in /etc/default/grub append dolvm to GRUB_CMDLINE_LINUX.
4. don't forget to regenerate grub2 config file after you modify /etc/default/grub, e.g. grub2-mkconfig -o /boot/grub/grub.conf.
5. reboot.