A question about upgrading versions of kvm and the guest image

A question about upgrading versions of kvm and the guest image

[Mark Ryden]

Hello,

I had build kvm from sources and then installed a
a guest according to kvm howto using qemu-system-x86_64.

(/usr/local/kvm/bin/qemu-system-x86_64 -hda vdisk.img -cdrom
/path/to/boot-media.iso \
   -boot d  -m 384)

The qemu-system-x86_64 utility is built when you build kvm from sources.

It was with kvm-49; now, I think to upgrade to the latest version of
kvm (kvm-55);
my question is:
should I repeat the process of creating the guest image using the
qemu-system-x86_64?
Or can I use safely the old vdisk.img guest image ?

And in general: when upgrading from current version of kvm to a newer one -
can I use the old guest image (which was created with current
qemu-system-x86_64)?
Or must the process of creating an image should be repeated with the new
qemu-system-x86_64 from the new version?

rgs,
Mark

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Re: A question about upgrading versions of kvm and the guest image

[Avi Kivity]

Mark Ryden wrote:
> Hello,
>
> I had build kvm from sources and then installed a
> a guest according to kvm howto using qemu-system-x86_64.
>
> (/usr/local/kvm/bin/qemu-system-x86_64 -hda vdisk.img -cdrom
> /path/to/boot-media.iso \
>    -boot d  -m 384)
>
> The qemu-system-x86_64 utility is built when you build kvm from sources.
>
> It was with kvm-49; now, I think to upgrade to the latest version of
> kvm (kvm-55);
> my question is:
> should I repeat the process of creating the guest image using the
> qemu-system-x86_64?
> Or can I use safely the old vdisk.img guest image ?
>
> And in general: when upgrading from current version of kvm to a newer one -
> can I use the old guest image (which was created with current
> qemu-system-x86_64)?
> Or must the process of creating an image should be repeated with the new
> qemu-system-x86_64 from the new version?
>   

You should be able to run with no problems immediately after upgrading.
If it doesn't work, please report how, what guest you are using and what
is your host cpu version.

There may be a problem if kvm changes its reported cpuid string and the
guest is sensitive to that, but otherwise it should just work.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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