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Re: [Xen-users] As a vps tenant using a DomU ubuntu 10.04, how would you upgrade kernels and OS?

On Fri, Jun 17, 2011 at 10:02 AM, Todd Deshane <todd.deshane@xxxxxxx> wrote:
> On Tue, Jun 14, 2011 at 9:05 PM, John Griessen <john@xxxxxxxxxx> wrote:
>> As a vps tenant using a DomU ubuntu 10.04, how would you upgrade kernels and
>> OS?

Depends on how the domU is setup:
- is it HVM or PV?
- if it's PV, does the kernel come from dom0 or domU (e.g. with pygrub)

>> I am interested renting a low cost server, but they offer no help, so here I
>> go asking you all...

The lowest cost VPS I can find was an Openvz VPS with 128MB RAM for
$15/year, while Xen VPS typically start around $5/mo. However, i do
NOT recommend using either for anything serious or critical since
you'll most likely be I/O-starved. Depending on how it's setup, there
are times when I wouldn't recommend upgrading the kernel either. Often
it's best to use whatever they currently provided, and only upgrade
the userland parts.

>> I did an experiment with apt-get to change kernels and  it worked with some
>> odd problems
>> to use a kernel called linux-image-2.6.32-316-ec2
>> <http://packages.ubuntu.com/lucid/linux-image-2.6.32-316-ec2> and it would
>> boot.
>> When I tried installing linux-image-2.6.32-32-server
>> <http://packages.ubuntu.com/lucid-updates/linux-image-2.6.32-32-server> it
>> would not boot.

> My guess it that for some reason the xen drivers are not being loaded
> for this kernel as they are in the ec2 version of the kernel. Check
> the config for this kernel that is stored in /boot. You should be able
> to either install another kernel package that was properly configured
> or use apt-get source on the linux image and add in the Xen-related
> drivers.

It should work, as both i386 and amd64 -server version contains the
necessary xen domU drivers (e.g. xen-blkfront). Can you access domU's
console while it's booting? Try removing "quiet" and "splash" kernel
arguments, and look at the boot logs. Does it detect the correct disk
during boot? It's possible that -server, -virtual, and -ec2 kernels
detect the disks differently (e.g. sda vs xvda) which might cause a
problem if you use /dev/xvda* entries instead of LABEL or UUID.

I usually use amd64, with linux-image-virtual that works just fine for
both PV and HVM domU.

>> I am thinking
>> that with Xen, the running kernel is not anything to do with the guest OS,
>> and
>> only the kernel modules come from the guest.

That's what happens when the kernel is on dom0. With HVM or
PV+pygrub/pv-grub, the kernel comes from domU as well.

>> If so, how would one upgrade kernels on a rented virtual server instance?

Depending on the setup, sometimes the answer is "don't bother"

>> Do you need help from the landlords?

Good "landlords" should provide support which can answer that :)

As an alternative, there are some dedicated server providers that rent
out atom/athlon/celeron-based server with 4G of RAM for about $50/mo,
so depending on your needs it might be a better choice.


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