Moving a server over to a RAID

Rashkae ubuntu at
Thu Aug 19 17:31:22 UTC 2010

Mike A. Leonetti wrote:

> If the hostname will be an issue I can always create the array first on
> the system and do a rebuild from the recovery CD. The rebuild shouldn't
> change any information then and I can copy the data and just change the
> boot flag and grub settings.

That wont help,, in fact, that's exactly how I ran into this issue. 
When you create the raid array from a working and booted system, that 
array will inherit the system hostname.  However, when Ubuntu boots into 
the initrd environment, it will not have this hostname. (initrd is 
basically a mini-linux install, that can fit into ram and contains 
enough tools to bootstrap the rest of the system, such as kernel modules 
and hotplug to detect all your devices, tools to find filesystems by 
UUID or LABEL, and mdadm to assemble raid arrays. )

It's not a big problem. It just surprised me at first since this was, 
for me, a relatively new kink to an old process, and when I first saw 
the message that root filesystem could not be found, dumping to busybox 
shell, I thought I had somehow royally buggered it up.  It was, however, 
easy to fix and get going from there with a bit a patience and reading 
of man mdadm.

> I'm also worried about not having all of the correct packages installed.
> When looking online I see a lot of howtos on created an array in Ubuntu,
> but only on install. Having not selected that option upon install I'm
> not sure if all of the kernel modules have been included, etc.

You will be fine in that regard.  All packages needed for raid are part 
of the default core system.

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