bug#31365: libvirt/virt-manager: Embeds full path to qemu-system in saved .xml files

[Mike Gerwitz <mtg@gnu.org>]

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On Fri, May 04, 2018 at 17:01:03 -0700, Vagrant Cascadian wrote:
> When i create a new libvirt instance with virt-manager, it embeds the
> full path to the qemu binary used at the time. For the machine named
> "networkboot":
>
>   # grep qemu-system /etc/libvirt/qemu/networkboot.xml
>   <emulator>/gnu/store/0rzb7rjri2kb258j58asndw2pnp0xv9p-qemu-2.11.1/bin/qemu-system-x86_64:</emulator>
>
> If I later run "guix gc" and it happens to remove this particular qemu
> version, the system no longer runs, of course:
>
>   # virsh start networkboot
>   error: Failed to start domain networkboot
>   error: Cannot check QEMU binary
>       /gnu/store/0rzb7rjri2kb258j58asndw2pnp0xv9p-qemu-2.11.1/bin/qemu-system-x86_64:
>       No such file or directory

Thanks for looking into this; I hit this problem last night but hadn't
had the time to research.

I encountered this issue the same way (after a `guix gc').

> It also means each virtual machine may be running on an older version of
> qemu, for better or worse.

Yes, I was concerned by that as well. :X  VMs would not benefit from
security fixes, which is to me is the more important issue here.

-- 
Mike Gerwitz
Free Software Hacker+Activist | GNU Maintainer & Volunteer
GPG: D6E9 B930 028A 6C38 F43B  2388 FEF6 3574 5E6F 6D05
https://mikegerwitz.com

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