XEN questions

Garrett Cooper youshi10 at u.washington.edu
Mon Jul 30 05:22:08 UTC 2007

Rakhesh Sasidharan wrote:
>> Does one run XEN inside of freebsd and then VMs inside that, or does
>> one run XEN on the bare hardware and then run freebsd inside that?  If
>> I've already got freebsd running on my box, do I have to reload it
>> from scratch or is there a way I can virtualize what I already have
>> runing?
> Hi,
> Xen runs on the bare hardware and other OSes run atop Xen (i.e. they are
> specifically "ported" to the Xen "hardware"). But you don't have to
> install Xen on the bare hardware as such. Typically you install Xen on
> your OS. And then you install other OSes on this Xen installation. That's
> how it works.
> For example: Say you are running FreeBSD 7.0. You install Xen on FreeBSD
> 7.0. Then you install FreeBSD 6.2 and NetBSD 3.1 onto Xen. In Xen
> terminology, all these OS installations (including the FreeBSD 7.0 on
> which Xen is installed) are called "domains". The FreeBSD 7.0 Xen domain
> is called dom0 (domain 0). While the FreeBSD 6.2 and NetBSD 3.1 Xen
> domains are called domU (domain User).
> dom0 is special coz that's what manages the other domains. Plus, that's
> where you install Xen first for it to interact with the hardware etc. Not
> all OSes support Xen on dom0. FreeBSD 6.2, for instance, doesn't. (It only
> supports domU). FreeBSD 7.0 would, I believe. NetBSD 3.1 does. In Linux,
> you need kernel 2.6.18 and greater I think.
> So to answer your question, if you are on FreeBSD 6.2, you can't try out
> Xen. You can, however, install FreeBSD 6.2 atop any Xen installation
> running on FreeBSD 7.0 and Linux or NetBSD 3.1 etc.
> Hope this helps. :)
> Regards,
> Rakhesh
> ps. This should be of some info --
> http://tx.downloads.xensource.com/downloads/docs/user/#SECTION01140000000000000000.

dom0 isn't all the way yet either, though rink@ has said that support 
might be in 7-CURRENT prior to the first release. We'll see what 
happens, since he's a busy college student.

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