Raid1 + LVM + Syslinux [SOLVED]

Tha-Fox · 2012-01-25 14:51:17

I'm trying to install Arch on my desktop with two disks. I try to set my /boot and swap on Raid1 array and / on Raid1 and LVM. After installation the system won't boot up because root file system is missing. I can't make changes to configuration because raid arrays won't assemble complaining about missing super blocks if I try that on live-cd.

Here is a brief summary of my installation process. I followed this guide.

I created three partitions on both disks with gdisk. I set "legacy BIOS bootable" on both disks. Then I created three raid1 arrays, md1 consisting of sda1 and sdb1 etc. Md1 is for /boot, md2 for swap and md3 for LVM. I created /boot with option "--metadata=1.0" as I understood that Syslinux can't handle newer. After that I added md3 to LVM and created one volumegroup "juurivg" and one logical volume "juurilv".

Then I added dm_mod module to the MODULES list in /etc/mkinitcpio.conf and mdadm and lvm2 hooks to the HOOKS list in /etc/mkinitcpio.conf after udev. I'm not sure, but I may have typed "dm-mod" to MODULES.

Finally I installed Syslinux and the configuration it gave looked sane. I tried to reboot and got this:

Starting udev...done
Running Hook [udev]
Triggering uevents... done
Running Hook [mdadm]
Running Hook [lvm2]
Activating logical volumes...
No volume groups found
Waiting 10 seconds for device /dev/mapper/juurivg-juurilv
ERROR: Unable to find root device /dev/mapper/juurivg-juurilv
You are being dropped to a recovery shell

So I assume I first have to get to the live-cd environment and get the RAID arrays assembling before I can modify any files. Any thoughts for that? If I follow for example this guide I stop in here.

mdadm --examine --scan /dev/sda1 >> /etc/mdadm/mdadm.conf

It writes nothing to config file.

Can I somehow mount the LV from rescue shell and try to boot that way?

Last edited by Tha-Fox (2012-02-14 14:09:21)

Cilyan · 2012-01-25 16:22:26

I'm struggling with the same problem...
It seems that mdadm correclty recognises the RAID, as all the partitions are available and can be mounted from /dev/md/* But there are no entries in /sys/block...
In your case, you can try with

mdadm --examine --scan /dev/sda >> /etc/mdadm/mdadm.conf

Last edited by Cilyan (2012-01-25 16:32:38)

cybertorture · 2012-01-25 16:38:40

mdadm --examine --scan /dev/sda1 >> /etc/mdadm/mdadm.conf

i dont see a reason of /dev/sda1
proper way should be:

mdadm --examine --scan >> /etc/mdadm.conf

also include /etc/mdadm.conf in /etc/minitcpio.conf in "FILES" section
edit: 1 more thing, add "raid1" module to /etc/mkinitcpio.conf in "MODULES" section and rebuild image

Last edited by cybertorture (2012-01-25 16:42:55)

Tha-Fox · 2012-01-26 14:09:04

Thank you for your suggestions! Now the only problem is to get hands on those configuration files. Here is what I've tried so far.

When I fell back to rescue shell during the boot, I tried to find my lvm volumes and mount the root filesystem manually but vgscan found no volume groups. I couldn't find any RAID tool either so I decided to try live-cd environment.

I booted from Ubuntu 10.04 live-cd. First I installed mdadm and lvm2. Then I gave following commands

modprobe raid1
modprobe dm-mod
modprobe dm_mod (tried this since I wasn't sure whether it's a dash or the underscore. Both went through without error.)
mdadm --examine --scan /dev/sda >> /etc/mdadm/mdadm.conf

The last one went through within a second and nothing showed up in mdadm.conf. I double checked that by running

mdadm --assemble --scan 
No arrays found in config file or automatically.

mdadm -A /dev/md1
mdadm: /dev/md1 not identified in the config file.

mdadm -A /dev/md1 /dev/sda1 /dev/sdb1
mdadm: cannot open device /dev/sda1: No such file or directory
mdadm: /dev/sda1 has no superblock - assembly aborted.

Can GPT somehow affect this? The last effort was to create /etc/mdadm/mdadm.conf manually. It looks now like this.

ARRAY /dev/md1 level=raid1 metadata=1.0 num-devices=2 devices=/dev/sda1,/dev/sdb1
ARRAY /dev/md2 level=raid1 metadata=1.2 num-devices=2 devices=/dev/sda2,/dev/sdb2
ARRAY /dev/md3 level=raid1 metadata=1.2 num-devices=2 devices=/dev/sda3,/dev/sdb3

But still...

mdadm: no devices found for /dev/md1
mdadm: no devices found for /dev/md2
mdadm: no devices found for /dev/md3

Tha-Fox · 2012-02-12 13:23:10

I think I found at least one error. In wiki's LVM-page it says:

If your root filesystem ( "/" ) is put onto a logical volume, make sure regenerate kernel image based on above modified /etc/mkinitcpio.conf by using below command so that bootloader can find your root during booting
     cd /boot 
     mkinitcpio -p linux 

But if I try that command while installing, it gives error:

invalid kernel specifier: '/boot/vmlinuz-linux'

I understand that because the files are in /mnt/boot but how can I tell that to the command? Should I first chroot myself in /mnt?

cybertorture · 2012-02-12 15:04:18

Should I first chroot myself in /mnt?

Yes, also do not forget to mount procfs /dev and probably /sys

jasonwryan · 2012-02-12 21:36:50

Tha-Fox wrote:

Should I first chroot myself in /mnt?

Yes. I've just been through a similar experience, except with legacy grub. Here are my notes.

Tha-Fox · 2012-02-14 14:08:57

Thanks you a lot, jasonwryan and cybertorture! Now it works! I missed regenerating the image first time. Now as I did it, root was found succesfully. I noticed some text about "generating image" when I chose "Done - Return to Menu" in AIF. I guess that is not enough though if you have / on LVM.

Last edited by Tha-Fox (2012-03-07 13:43:48)

Arch Linux

#1 2012-01-25 14:51:17

Raid1 + LVM + Syslinux [SOLVED]

#2 2012-01-25 16:22:26

Re: Raid1 + LVM + Syslinux [SOLVED]

#3 2012-01-25 16:38:40

Re: Raid1 + LVM + Syslinux [SOLVED]

#4 2012-01-26 14:09:04

Re: Raid1 + LVM + Syslinux [SOLVED]

#5 2012-02-12 13:23:10

Re: Raid1 + LVM + Syslinux [SOLVED]

#6 2012-02-12 15:04:18

Re: Raid1 + LVM + Syslinux [SOLVED]

#7 2012-02-12 21:36:50

Re: Raid1 + LVM + Syslinux [SOLVED]

#8 2012-02-14 14:08:57

Re: Raid1 + LVM + Syslinux [SOLVED]

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