Xen users - Dec 2007 - Converting the full-virtualization to para-virtualize

I got a question here. Can I install a full-virtualized fedora 7 as dom0
then convert it into para-virtualized?

It''s because I had tried faced so many errors when installing the
para-virtualized  fedora7 with the nfs server. 

 

--Stephen Neohtm,Malaysia

 



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I don''t know whether there''s a convenient tool for this.

I did once from a standalone machine (no PV in that case).
Basically you have to install a domU kernel and copy the root files to the new 
root accessible directly by dom0 (no partition tables, no bootloader) and 
change files such as /etc/fstab and the initrd.

If your dom0 is the same OS as the domU, things may be a bit easier.
Perhaps just copying the files, modifying fstab then chrooting and installing 
the domU kernel will be enough (no manual changes to inittrd).
I never tried this specifically, though.

If you''re able to configure the OS by hand, and your dom0 is also a
Fedora OS
you can simply:
$ rpm --root=/your/domU/root -ivh blah blahblah blah blah
Then, when things are done and your domU is fully funcional you may simply 
copy the root contents as a skeleton for future domUs you may want to create 
in the future.


Em Dom 02 Dez 2007 04:21, neohtm escreveu:
> I got a question here. Can I install a full-virtualized fedora 7 as dom0
> then convert it into para-virtualized?
>
> It''s because I had tried faced so many errors when installing the
> para-virtualized  fedora7 with the nfs server.
>
>
>
> --Stephen Neohtm,Malaysia
-- 
 Daniel Mealha Cabrita
 Divisao de Suporte Tecnico
 AINFO / Reitoria / UTFPR
 http://www.utfpr.edu.br

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> I got a question here. Can I install a full-virtualized fedora 7 as dom0
> then convert it into para-virtualized?
>
> It''s because I had tried faced so many errors when installing the
> para-virtualized  fedora7 with the nfs server.
I assume you meant installing a paravirtualised F7 as domU, not dom0?  (if it 
were dom0 you could just use the F7 installer and specify that you wanted 
virtualisation).

Converting it in this way should be fairly straightforward.  Use yum in your 
domU and get it to install the F7 Xen-enabled guest kernel (don''t
install the
Xen package itself, you don''t want the hypervisor or tools).  This may 
configure a guest entry in grub automatically, or you may have to add one for 
your guest kernel and initrd manually - I''ve not used F7 much, so
I''m not
sure.  Then you need to change the configuration for the domain to be 
paravirtualised...

I assume you''re using virt-manager?  I don''t know if the
version in F7 stores
config files in /etc/xen/?  In which case you could just copy / alter those 
config files to conform to a PV guest.  If not, I understand you can 
use "virsh" to dump the config file into XML form, then modify it,
then
reload that file to change the config used for the domain.

To convert it to PV you''ll basically want to remove all the HVM-isms
(e.g.
stuff like the ioemu devices, the hvmloader, the builder, etc may need to be 
changed) and add in the relevant PV-isms (e.g. different syntax for 
describing virtual framebuffer, "linux" builder, pygrub bootloader,
device
names changed to xvd*).

Then if you boot the domain with xm create -c you ought to see the pygrub 
screen appear; select the Xen-enabled grub entry that you installed.  It 
should boot (fingers crossed).

If you keep a copy of the original HVM config you should be able to switch 
between the two fairly easily for debugging purposes.  If you installed the 
guest to use partitions, not LVM, then it''s trivial to mount the
guest''s
filesystem from dom0 to make tweaks.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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