Re: [Qemu-devel] Are VM snapshots on Ubuntu host compatible with Fedora host?

[David Barrett <dbarrett@quinthar.com>]

andrzej zaborowski wrote:
> On 01/04/2008, David Barrett <dbarrett@quinthar.com> wrote:
>> Anthony Liguori wrote:
>>  > David Barrett wrote:
>>  >> Following up on this, I created a brand-new WinXP image from scratch
>>  >> (on my Ubuntu box), uploaded to my headless Fedora box, and it still
>>  >> has the  exact same crash:
>>  >>
>>  >> qemu: warning: error while loading state for instance 0x0 of device 'ram'
>>  >> qemu: fatal: triple fault
>>  >>
>>  >> So is it safe to say that QEMU VM snapshots are not transferable
>>  >> between hosts?
>>  >
>>  > KVM images are not compatible with QEMU.  If one of your servers is
>>  > running KVM, that's likely your problem.
>>
>>
>> Ahh, very interesting.
>>
>>  Just to make sure I understand correctly, this means VM snapshots made
>>  when QEMU has KQEMU enabled will not transfer between machines, right?
> 
> No, as long as you are using qemu (with kqemu or without) an image
> should run identically on any host. Unless you're using kvm on one of
> the hosts, what you're seeing is some bug.

Good, thanks for that information.  I don't think KVM is on any of the 
systems, but how can I confirm this?

At any rate, the "kvm" package hasn't been installed on either of the 
Ubuntu boxes -- both of which work -- and I'm not sure how to check on 
the Fedora Core 4 box (but I note /dev/kvm doesn't exist, and "yum list 
| grep kvm" comes up blank).


So in summary, everything works perfectly on two different Ubuntu 7.10 
boxes (one single-core laptop, one dual-core desktop), but doesn't work 
on the quad-core Fedora Core 4 box.  In all cases, I'm using the exact 
same qcow2 file, and starting with the exact same command line:**

qemu -monitor stdio -serial vc -smb qemu -kernel-kqemu -localtime -m 512 
-loadvm boot winxp.qcow2

** I add "-vnc :0" to the FC4 command line as it's a headless server.

The one ray of light is I can get it to partially work on the FC4 box by 
removing "-loadvm" from the command line.  However, then the WinXP image 
just BSODs immediately after the countdown timer to boot selection 
(Start Windows Normally).  So, no luck, despite being the same image as 
works under Ubuntu.  (Seems to use 100% CPU under Fedora, as well.)

What's the proper command line to use for a headless server?  "-vnc :0" 
seems to work fine -- I'm able to VNC in and watch it repeatedly BSOD, 
at least -- but I'm thinking maybe the lack of physical video or audio 
card might be causing Windows to crash?  I've tried these options, but 
nothing helped:

-nographic: Seems to start, but can't connect via VNC
-no-acpi: No effect
-std-vga: No effect

The BSOD reboots instantly so it's hard to tell what it's complaining 
about, but it looks like something with an IRQ -- and perhaps something 
about it being less than something else.  Not very helpful, I realize, 
but it's all I can get.

Any suggestions for how to get this thing to work on a headless server?

I'm going to try a couple other servers (one is running a Debian-based 
environment), so I'll let you know how that goes.

Thanks for all your help!

-david