[Xen-users] Re: Can Dom0 be replaced after installation?

[Mike Fröhner <mikefroehner@xxxxxx>]

Am 12.08.2010 09:00, schrieb Fajar A. Nugraha:
> On Thu, Aug 12, 2010 at 12:30 PM, Ken<kr.xen@xxxxxxxxxxxxx>  wrote:
> > Hi,
> >
> > Agonizing about a strategy for installing, when I know nothing about it.
> > I suspect that in spite of the flexibility in choices for a dom0
> > operating system, I think it's probably really important to get it all
> > right.
> At this point I usually say "it depends".
> xenserver/XCP is designed for those who wants a system that "just
> works" without having to worry about what the best dom0 setup is.
>
> > 1. Assuming I install Xen, a handful of VMs and have it all set up, is
> > there a way to replace dom0 with some other dom0?  If I knew I could
> > change my mind later it would be much easier to set this up.
> In principal, yes. A domU is basically defined by its configuration
> file and backing storage. If you have both, then you should be able to
> (re)create an identical domU using whatever dom0 hardware/OS.
>
> So assuming that the old and new OS both have access to the same
> storage (possibly include support for the same partition/LVM and
> filesystem type) and domU configuration, changing dom0 OS is possible.
> Moving from (for example) Centos to Opensuse is easy enough, but
> moving from Centos to opensolaris is somewhat hard.
>
> > 2. There seems to be a way to have a kernel which works either on the
> > bare metal or as a guest, but it doesn't seem to have been tested much.
> > Do I ignore this for now, and if I do can I start using it later?
> Since you're new to Xen, I suggest using dom0 with bundled Xen. My
> favorite is RHEL5. Although its version of Xen is slightly out of date
> in terms of features, it's enough for most common use, and kept
> up-to-date in terms of bugfix/security update.
>
> >   If I
> > change it on Dom0 do I need to recompile kernels on the other guests?
> No. domU can be independent of dom0 kernel.
>
> > 3. I keep expecting to need to install the hypervisor somewhere.  I
> > don't see the hypervisor anywhere in Gentoo, but there's xen-sources
> > which I suspect contains it.
Try: http://en.gentoo-wiki.com/wiki/Xen
> Try asking on Gentoo list
> on RHEL/Centos it's simply "yum groupinstall Virtualization"
>
> >   Or do I need the tarball from
> > www.xen.org/products/xen_source.html?
> Possible, but it might not be so straightforward. See
> http://wiki.xensource.com/xenwiki/Xen4.0
>
> > 4. In my understanding the dom0 needs to be extremely stable and have
> > good driver support.  What distro works best for that?  I'm currently
> > using Gentoo, but I would think Debian would be most stable.  If so, is
> > the current difficulty with Debian an unhappy coincidence or is it
> > consistent?  How about Ubuntu Server, or is that still the same problem
> > since it's also a Debian?  What do people use if they just want a small,
> > stable dom0 with good driver support?
> I like RHEL.
>
> > 5. Is there a way to "loan" processors to a guest if nobody else is
> > using them?
> By default all domUs have the same priority. See
> http://wiki.xensource.com/xenwiki/CreditScheduler


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