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I installed ubuntu server 10.04 on a PC with two HD drives 500 GB each. I used raid1 to provide data protection.

After the installation has completed, the system did not boot properly. I got the following error message:

ALERT! /dev/disk/by-uuid/$UUID does not exist. Dropping to a shell!

I tried the following scenarios:

1- Installing the /boot partition on a mirrored device /dev/md0.

2- Installing the /boot partition without raid1.

3- Installing the system without raid at all.

I got the same error in cases 1 and 2. However, the system booted as it should do in case 3.

Any idea what could cause such a problem? Can't I install ubuntu server on these HD drives with raid1?

share|improve this question
At seems like there is a problem with the raid-configuration. Are you sure you installed the system into /dev/mdx and not dev/sdx? Can you provide the output of sudo fdisk -l? – Bobby Nov 15 '10 at 13:40
@Bobby: I tried both cases: installing the /boot on /dev/mdx and /dev/sdx. These are the case 1 & 2 shown in the question. Currently, I can't provide the output of fdisk as I was trying to re-install the system. Which case are you interested in (1 or 2)? – Khaled Nov 15 '10 at 13:49
Are you using a Soft- or Hardware raid? And was that the whole error message or was their also a UUID provided? – Bobby Nov 15 '10 at 13:54
Ah, I see...markup ate it. Seems like there changed something from the you need an extra boot partition or can you leave it in /? – Bobby Nov 15 '10 at 13:57
Thanks for editing the question! I am using Linux software raid (MD). For the boot partition, I can leave it in / if it will work :) – Khaled Nov 15 '10 at 13:59
up vote 0 down vote accepted

An all-RAID-1 installation is supposed to work out of the box (at least with the server installer). I don't know what could have gone wrong for you.

If you run into that problem again, try changing root=UUID=… to root=/dev/md0p1 (or whatever the right number is) in the linux line at the Grub prompt.

If that doesn't work either, you can boot on one of the components of the mirror, e.g. /dev/sda1. Make sure to set the other component as faulty with mdadm /dev/md0 --fail /dev/sdb1 before you do anything RAID-related. If you manage to get a command line, run update-initramfs -u. Then try rebooting on /dev/md0p1.

If you manage to boot on the RAID device, either figure out what the right uuid for your root partition is (it might be as simple as running update-grub), or alternatively set GRUB_DISABLE_LINUX_UUID=true in /etc/default/grub and run update-grub.

share|improve this answer
Thanks for your advice. I will try it and let you know! – Khaled Nov 16 '10 at 8:19

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