fresh install over ssh

[Patrick Asselman]

This is a continuation of an old thread where we discussed upgrading a 
32bit system to 64bit using remote access via ssh.

On 2013-04-26 13:48, Avi Greenbury wrote:
> Patrick Asselman wrote:
>> There is no rescue environment yet. The box has an ILO but as far as
>> i know that does not give you a full linux shell environment. There
>> is also an unused disk, so I thought of using that. So now the
>> general idea is to use debootstrap to install a chroot environment
>> on the new disk first, then reboot into that, and repeat the process
>> on the original boot partition to get the 64 bit stuff on there.
>> (The extra disk is meant to be a swap disk eventually).
>
> That all sounds good, though as an aside I do question the need for
> swap generally, let alone spending an entire drive bay on it :)
>
>> Are there any things to watch out for (especially Grub-related
>> things?)
>
> It's been a while since I last used debootstrap, but I recall it
> being tedious more than difficult. At worst you can chroot into the
> new environment and treat it as if you'd booted straight onto it.

I've been playing around in a VM to test this before actually doing it 
on the server. It turns out that one cannot chroot from a 32bit Linux 
into a 64bit shell :-(  (The other way around is possible, but only 
because a 64bit kernel can understand 32bit stuff).

>> It sounds like I should probably test this on a VM at home first, to
>> get a bit more comfortable with the whole procedure. Especially Grub
>> is something i'm not familiar with at all, but I'm glad it does not
>> sound impossible :-)
>
> Yeah, you shouldn't need to do anything directly with grub, but it's
> definitely worth playing with it for a bit first. Perhaps even
> configure the new system on a VM then rsync the volume onto the disk
> on the server, before chrooting into it and installing grub? That
> would assume no unusual hardware on the server.

Since the debootstrap wasn't working, I now tried a new approach: 
boldly overwrite all the 32bit stuff with 64bit stuff, starting with the 
kernel. This procedure is described here: http://www.ewan.cc/?q=node/36

Unfortunately I now hit a new snare. After placing a new 64bit kernel 
in /boot, updating grub to boot that new kernel, and rebooting, the 
kernel panics. From the messages on screen I suspect this is because the 
boot partition is located on a logical volume. This is what I get:

VFS: cannot open root device "mapper/ubuntu32-root" or 
unknown-block(0,0): error -6 Please append a correct "root=" boot 
option; here are the available partitions:
0800 8388608 sda driver: sd
  0801 248832 sda1 00000000-0000-0000-0000-000000000000
  ...
Kernel panic - not syncing: VFS: unable to mount root fs on 
unknown-block(0,0)


The grub.cfg does have the correct disk UUID, which is exactly the same 
as it is on the 32bit kernel which booted fine.

So the next question is: can I place some 64bit software for the 64bit 
kernel so that it can boot from the LVM?
Which software (package?) is required, and how do I install this?


Best regards,
Patrick Asselman