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Re: [Xen-users] How to change VM from para-virtualization to full-virtualization?

  • To: Alexandre Kouznetsov <alk@xxxxxxxxxx>, "xen-users@xxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxx>
  • From: Jing Chen <jing.chen@xxxxxxxxxxxx>
  • Date: Mon, 12 Nov 2012 02:02:26 +0000
  • Accept-language: en-US
  • Delivery-date: Mon, 12 Nov 2012 02:04:04 +0000
  • List-id: Xen user discussion <xen-users.lists.xen.org>
  • Thread-index: AQHNvptdoOJcEJrDNUuWIn8Y5wXmE5fldXyA
  • Thread-topic: [Xen-users] How to change VM from para-virtualization to full-virtualization?

Hello. Alexadre.
    I post it in the web site. Can you log on it to check 

You can see all the scree shot there. 

Looking forward your quick response.


Jing Chen

No.5 Lize East Street, Chaoyang District
100102, Beijing, China
Phone +86 10 84767586
Mobile +86 13801223973


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-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxx] 
On Behalf Of Alexandre Kouznetsov
Sent: Saturday, November 10, 2012 12:54 AM
To: xen-users@xxxxxxxxxxxxx
Subject: Re: [Xen-users] How to change VM from para-virtualization to 

Hello, Jing.

(Sorry if this is repeated. I don't see this mail I sent since yesterday in the 
list, so I re-send it.)

It's something wrong with your e-mail formatting, the screenshots you attached 
are not displayed inline.

Please consider not using HTML formatting when sending mails to the list. If 
you wish to share the output you get from your system, post or attach it as 
plain text.

El 08/11/12 01:53, Jerry Gao escribió:
> *From: *Jing Chen
> *Sent: *Thursday, November 08, 2012 2:14 PM
>       This is Jing and I work with Jerry for this issue. I saw your 
> email and do some test following your instruction. As our case, I met 
> lots of issues since there are lots of track as you said. I list them 
> here and need your help to check.
> Seems it is a little bit longger. But your help is grateful.

> I create a PV for DomU and install the SUSE linux 11 SP2. my 
> configurations are as below.
> 1) partition.
I guess this is the screenshot showing "expert partitioner". As I understand 
it, this is how your PV guest looks initially and you use
/dev/xvda2 as LVM physical volume. /dev/xvda2 seems to be a true partition 
within /dev/xvda, to you already have a partitioned block device for you HVM.

> 2) /etc/fstab file
Looks fine to me. Since your guest uses LVM, the device names are expected to 
remain unchanged after you switch to HVM, except /dev/xvda1 for /boot.

> 3) /boot/grub/menu.lst
>      in PV, grub has been installed. The option 0 is the one work 
> normally in PV. I add the second option for HVM.
Note, that since your /boot is on separated partition, the path to kernel and 
initrd are wrong. As you specify it, they would be searched under /boot/boot.
Remove the "/boot" prefix from pathnames of kernel and initrd images, your 
files are on "root" of your /boot partition.

> 4) the conf file in Dom0 is as below.
As I see, your DomU's xvda resides on your Dom0's /dev/sda4. This is not 
something I would recommend becouse of risk of confusion, one between many 
others). But should work if you are careful enough.

As a note, personally I use LVM within Dom0 (not DomU) and export multiple 
logical volumes as the DomU needs them. This instead of exporting a single 
block device and manage it's volumes within DomU.

> To chagne PV to HVM. I do the following modification.
> 5) change conf file in Dom0
boot="d" should make you boot from CDROM, I'm not sure if that's your intention.
In any case, it's good idea to boot a liveCD first, specially to take a look 
how the storage is presented to the DomU and make sure the boot loader is 
correctly installed.

So, does it boots from ISO?

> 6) change /etc/fstab as below
Looks good, but will work only if your LVM infrastructure is correctly 

> 7) change /etc/mtab as below
/etc/mtab is usually auto-generated, in rare cases it needs to be modified by 
hand. In some occasion I had to do it to trick grub installer to place it's 
code in the correct place.

> Then. I start up the HVM using xm create command. And the error is as below.
>    I try to change root parameter in menu.lst, such as "root=/dev/hda2".
> But it still can not startup saying can not mount /dev/hda2 to root.
Actually, it complains about mounting /dev/vg69/root. Not /dev/hda2, which is 
your physical volume, not root filesystem. (Am I looking to a wrong place?)

You have a rather complex storage setup. One of the benefits of virtualization 
is that you can hide this complexity from the VM, keeping it very simple, very 
small, very stable. Caesar's to Caesar, and infrastructure management to Dom0.

In this case, I bet initrd does not have LVM support, that's why it can't see 
/dev/vg69/root. Please consult your distribution documentation, about how to 
re-build initrd. Surely it's a very automated process.

> Please give your advise what can I do.
Consider this steps:
1. Boot using the VM using your distribution's live CD in some "rescue" 
2. Make sure your /dev/hda, and all it's partitions and logical volumes are 
readable and mountable.
3. Threat this case as a normal, not virtualized machine that got something 
wrong with it's booting. Suse documentation shall cover it.

Alexandre Kouznetsov

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