Xen users - May 2007 - Migrating XEN VMs on CentOS 4.4 to CentOS 5

G''day All,

I have a number of VMs that I installed on CentOS 4.4 with custom  
dom0 and domU kernels.  All VMs reside on logical volumes and a
disk = [ ''phy:/dev/vg0/name,sda1,w'', ...]
type entry can be found in the XEN configuration file.  I have been  
searching on and off for a week (no success)  trying to find out how  
to move these VMs onto a CentOS-5 system - using the XEN  
implementation that comes with this O/S.

I suppose what I''m asking is how do I move existing VMs from sda to  
xvda disks within XEN.

Regards,

Wayne Mallett

Dr. Wayne Mallett
High Perf. & Research Computing Support
Information Technology & Resources
James Cook University
Townsville  Qld  4811
Australia

Ph (int):  5084
Ph (ext) :  07 4781 5084
Email:  Wayne.Mallett@jcu.edu.au




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Wayne Mallett wrote:
> G''day All,
>
> I have a number of VMs that I installed on CentOS 4.4 with custom dom0 
> and domU kernels.  All VMs reside on logical volumes and a
> disk = [ ''phy:/dev/vg0/name,sda1,w'', ...]
> type entry can be found in the XEN configuration file.  I have been 
> searching on and off for a week (no success)  trying to find out how 
> to move these VMs onto a CentOS-5 system - using the XEN 
> implementation that comes with this O/S.
>
> I suppose what I''m asking is how do I move existing VMs from sda
to
> xvda disks within XEN.
Don''t bother. Simply continue to use them as "sda" devices,
which is
what I do. Also, getting a non-standard kernel to operate correctly in 
paravirtualizd mode is going to be fun for you! I wound up using the 
xensource published kernel-xen-2.6.16 kernel for this.

If you really need to migrate to /dev/xdva names, you''ll need to edit 
/etc/fstab on the / partition to match the new layout, and edit your Xen 
configuration file appropriately.

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On Wednesday 9 May 2007 19:52, Nico Kadel-Garcia wrote:
> Wayne Mallett wrote:
> > G''day All,
> >
> > I have a number of VMs that I installed on CentOS 4.4 with custom dom0
> > and domU kernels.  All VMs reside on logical volumes and a
> > disk = [ ''phy:/dev/vg0/name,sda1,w'', ...]
> > type entry can be found in the XEN configuration file.  I have been
> > searching on and off for a week (no success)  trying to find out how
> > to move these VMs onto a CentOS-5 system - using the XEN
> > implementation that comes with this O/S.
> >
> > I suppose what I''m asking is how do I move existing VMs from
sda to
> > xvda disks within XEN.
>
> Don''t bother. Simply continue to use them as "sda"
devices, which is
> what I do. Also, getting a non-standard kernel to operate correctly in
> paravirtualizd mode is going to be fun for you! I wound up using the
> xensource published kernel-xen-2.6.16 kernel for this.
>
> If you really need to migrate to /dev/xdva names, you''ll need to
edit
> /etc/fstab on the / partition to match the new layout, and edit your Xen
> configuration file appropriately.
>
... And on top of that, the grub menu in the domU /boot/grub directory should 
be updated to use /dev/xdva names. If not, pygrub will not work correctly 
(presuming you are using pygrub, at least).

That was a problem I ran into.

Geert

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G''day All,

I read/heard(?) somewhere that xvda was the future and use of hda,  
sda, etc. was going to be phased out.  My main aim was to move  
xensource 3.0.3 VMs onto CentOS-5 (2.6.18-el5xen or subsequent  
kernel).  At present I have given up on the XEN distributed in CentOS  
5 and started working with XEN 3.1.0.  However, I would still be  
interested in knowing how to migrate VMs to the distribution  
installed XEN.  I tried an "xm migrate ..." but it didn''t
work (my
XEN is setup for host-to-host migrations and they have worked in the  
past).  I have also tried using the same xen configuration file and  
moving contents of the logical volumes around but the VM won''t boot  
on the new system.

Regards,

Wayne Mallett

On 10/05/2007, at 6:22 PM, Geert Janssens wrote:
> On Wednesday 9 May 2007 19:52, Nico Kadel-Garcia wrote:
>> Wayne Mallett wrote:
>>> G''day All,
>>>
>>> I have a number of VMs that I installed on CentOS 4.4 with custom  
>>> dom0
>>> and domU kernels.  All VMs reside on logical volumes and a
>>> disk = [ ''phy:/dev/vg0/name,sda1,w'', ...]
>>> type entry can be found in the XEN configuration file.  I have been
>>> searching on and off for a week (no success)  trying to find out
how
>>> to move these VMs onto a CentOS-5 system - using the XEN
>>> implementation that comes with this O/S.
>>>
>>> I suppose what I''m asking is how do I move existing VMs
from sda to
>>> xvda disks within XEN.
>>
>> Don''t bother. Simply continue to use them as "sda"
devices, which is
>> what I do. Also, getting a non-standard kernel to operate  
>> correctly in
>> paravirtualizd mode is going to be fun for you! I wound up using the
>> xensource published kernel-xen-2.6.16 kernel for this.
>>
>> If you really need to migrate to /dev/xdva names, you''ll need
to edit
>> /etc/fstab on the / partition to match the new layout, and edit  
>> your Xen
>> configuration file appropriately.
>>
> ... And on top of that, the grub menu in the domU /boot/grub  
> directory should
> be updated to use /dev/xdva names. If not, pygrub will not work  
> correctly
> (presuming you are using pygrub, at least).
>
> That was a problem I ran into.
>
> Geert
Dr. Wayne Mallett
High Perf. & Research Computing Support
Information Technology & Resources
James Cook University
Townsville  Qld  4811
Australia

Ph (int):  5084
Ph (ext) :  07 4781 5084
Email:  Wayne.Mallett@jcu.edu.au




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Xen-users mailing list
Xen-users@lists.xensource.com
http://lists.xensource.com/xen-users

Wayne Mallett wrote:
> G''day All,
>
> I read/heard(?) somewhere that xvda was the future and use of hda, 
> sda, etc. was going to be phased out.  My main aim was to move 
> xensource 3.0.3 VMs onto CentOS-5 (2.6.18-el5xen or subsequent 
> kernel).  At present I have given up on the XEN distributed in CentOS 
> 5 and started working with XEN 3.1.0.  However, I would still be 
> interested in knowing how to migrate VMs to the distribution installed 
> XEN.  I tried an "xm migrate ..." but it didn''t work (my
XEN is setup
> for host-to-host migrations and they have worked in the past).  I have 
> also tried using the same xen configuration file and moving contents 
> of the logical volumes around but the VM won''t boot on the new
system.
Yeah, RedHat seems to have done some serious oddnesses to fit Xen into 
their industrieal system management approach. Migrating *old*, 
customized systems is unlikely to work well..

I do *not* use internal LVM''s inside a Xen guest domain.
There''s little
point in it or in the unnecessary CPU overhead: leave the LVM work to 
occur on the host domain, not the guest domain.

I also don''t particularly like the insistince on using pygrub by the 
virt-install and virt-manager tools: Just install the kernel on the Dom0 
and leave it out of the DomU''s!

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