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RE: [Xen-users] Clear definitions

  • To: "Fabio Viero" <fviero@xxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
  • From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
  • Date: Thu, 5 Apr 2007 12:15:44 +0200
  • Delivery-date: Thu, 05 Apr 2007 03:14:57 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: Acd257iZ+MuvV/AxThqjGSAgGcytBQAgKASg
  • Thread-topic: [Xen-users] Clear definitions

> >
> >
> Let´s go for a practical example. Assume i´m using SLES10 and booting
> the Xen kernel that comes with the distribuition. Right? Let´s go
> ahead. I don´t like too much the yast way of doing things but let´s
> use it now. I create a virtual machine, the only option available is
> "paravirtualization" because i don´t have VT or V as processor. I will
> not lie now and tell you that i did install an unmodified linux OS
> (say stock Fedora). But i´ve read reports of people doing it. You
> said: "To run unmodified (any OS), you'll need a processor that has
> AMD-V or Intel VT.". I know i´m missing something here, as soon as i
> discover what is this "miss" i´ll probably head in the right
> direction. I´m afraid i still in need of some guidance :) and the
> question that arose is: wich is true on the above? i will NOT be able
> to install Fedora? or i WILL be able to run un unmodified OS, contrary
> to what you said?

Ok, let's take a step back and discuss what I mean by "unmodified". 

I'm pretty sure some people (for example XenSource, Virtual Iron, SuSE, 
RedHat/Fedora) have developed tools that allow you to install a guest from the 
base-install media (or at least that will help you through part of that 
process). [Of course, whether those tools allow you to install a Fedora image 
with SuSE tools or SuSE image with Fedora tools is a different matter - I don't 
know the answer to this]. 

However, if you don't have AMD-V or Intel VT on the processor, the kernel used 
in such an installation MUSST be one that uses a MODIFIED kernel. That is, a 
kernel that is specifically built to talk to Xen, rather than the kernel that 
you'd use for bare-metal (the hardware without Xen). This is what's meant by 
"modified" vs. "unmodified". The unmodified uses exactly the same binary image 
as you'd use on "bare-metal", which means that no special kernel is needed. 

With the virtualization extensions, you can just take the installation CD/DVD 
and set the virtual machine to say:
Your CD/DVD is this (either the physical device or an ISO-image). 
Your Hard-disk is this (a file, logical volume or physical device)

And off you go and install it, just like you would on bare-metal - the only 
difference is the fact that your "console" is a window instead of the full 


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