[mythtv-users] Virtualisation .. can it do this? (HP ProLiant MicroServer N40L)

Simon Hobson linux at thehobsons.co.uk
Tue Sep 25 16:09:20 UTC 2012

Damian wrote:

>I have noticed, from forums etc, that almost everyone who owns one 
>of these things uses some sort of technology to run different 
>virtual OS's on it. I couldn't really see the point of this unless 
>you are either a developer or an uber-geek (a term I use with the 
>greatest respect .. I am a merely a semi-geek). It just sounds to me 
>like there's more that can go wrong than if I was just running the 
>machine with a standard OS. And I had heard that USB tuners could be 
>a headache to get working in a virtual machine.
>I hate things that don't just work these days and can't bare the 
>headache when things go wrong (I must be getting old!)
>However, I did have a thought this morning.
>One thing that constantly trips my up with Mythbuntu is 
>upgrading/updating it. I know a lot of you would say, if it's not 
>broke, don't fix it. But I like to have the latest stable version of 
>So, my question is, could virtualisation help with this?

Yes, but I think it's probably overkill for what you want.

I bought one of the earlier N36L Microservers, with the intention of 
running MythTV and my other services on it. However I found that my 
tuners (PCIe, HVR-1300) didn't work with Xen loaded and more than 4G 
of physical RAM in the machine. Didn't work as in, in Dom0 they were 
recognised but any attempt to tune anything returned no data.
Since they were still on cashback I bought another for everything 
else and kept one just for Myth.

What I'd suggest is rather than going for virtualisation, use LVM for 
everything but a /boot filesystem*. Then it's fairly simple to just 
create additional LVs, clone your current system over to them 
(remembering to tweak things like /etc/fstab), and then reboot into 
the newly made copy. Your original remains safe and sound while you 
experiment - and when you are ready you can just make the new version 
your live system by setting the default boot entry in grub.
* If you do keep a physical partition for /, then you may want to 
keep another spare one for your tests.
Obviously you need to keep enough spare room in your LVM VG for any 
extra volumes you might need.

This does have the downside that you have to shut down your live 
system while working on the new one - but as long as you keep an eye 
on the schedules/upcoming recordings then it should be too hard to 
find reasonable windows to work in. On the other hand, since you'll 
probably need your hardware (tuners etc) for some of the 
testing/setup then you'd still need to shutdown your live system even 
if you were running full virtualisation.

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
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