[Bug 120375] Re: cannot boot raid1 with only one disk

Emanuele Olivetti emanuele at relativita.com
Mon Nov 9 10:08:15 GMT 2009

Hosed wrote:
> Hi, I have Ubuntu 9.04. I have Two (2) 36gb Seagate Cheetah with Raid 1
> - Mirroring Setup. When I boot to Ubuntu 9.04 with One (1) of the hard
> disks unplugged, it fails to boot, it drops me to a shell with
> initramfs. What's the deal with that? Does it mean that Raid1 is NOT
> WORKING with Ubuntu 9.04?
> Any help is greatly appreciated. Thanks.


I had a similar issue on Friday: a disk failed on a raid 1 ubuntu
9.10 system. After shutdown I removed the failed disk and added a new
one. While booting I got an initramfs shell, as in your case.

In my case the instructions on screen said that the system requested
me whether to boot with a degraded array (y/N) or not and that and I
did not answer quickly enough to the question, so, after timeout, it
brought me the initramfs shell. To be honest I never saw that question
on screen and the reason was that the splashscreen covered it.

So I just rebooted and pressed 'y' some times when the splashscreen
appeared and then the degraded boot started as expected. After
that I had to manually partition the new disk (I have 2 different raid1
systems, one for /boot, one for / ) and add each partition to the raid

sfdisk -d /dev/sda | sfdisk /dev/sdb  # partition sdb as sda
mdadm /dev/md0 -a /dev/sdb1    # add sdb1 to the raid1 system md0 (/boot)
mdadm /dev/md1 -a /dev/sdb2    # add sdb2 to the raid1 system md1 (/)

WARNING: this worked for my setting so don't take them as general instructions!
If you have a mirroring setup than you could need just to add sdb1. 

After this the new disk sdb started syncing as expected.



cannot boot raid1 with only one disk
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