Re: Moving a server over to a RAID



(2010年08月19日 12:09), Rashkae wrote:
Mike A. Leonetti wrote:
I have a server now that has one drive and is not set up on a RAID
using Ubuntu 8.04.

What I was going to do was boot with a Linux recovery disc, create a
RAID1 manually with mdadm on two new drives, and then copy all of the
data onto that then redo the boot partition.

My question is, when I reboot, will Ubuntu automatically detect the RAID
for me or are there modules I have to install ahead of time to make sure
the RAID gets detected? Also, would anybody else handle the situation
differently :D.

There is going to be one hurdle you'll need to get over.. I forget the
exact command I used to recover, but I'll give you the overview.

When raid array's are created, they are given a "hostname", which, by
default, will by the system hostname. By default, mdadm will not
auto-assemble raid arrays from a different hostname (to prevent
misunderstandings when hard drives are moved between different systems.)
Unfortunately, Ubuntu must assemble the raid arrays from the Initrd
system, which will probably not contain your hostname unless you have
customized it. I encountered this problem when I created the new array
from the existing system, I do not know if you will have this issue when
creating the array from the rescue cd.

When I tried to reboot the system, it was unable to mount the root
filesystem. However, initrd dropped me to a busybox shell, from which I
was able to run mdadm with options that would assemble the correct array
*and* update the hostname of the array, (which I think is simply "", ie.
empty, in initrd.)

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.

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.

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