[libvirt] [PATCH] m4: Change default QEMU credentials to qemu:qemu

[Andrea Bolognani]

On Tue, 2019-03-26 at 13:20 +0000, Daniel P. Berrangé wrote:
> On Tue, Mar 26, 2019 at 12:49:28PM +0100, Andrea Bolognani wrote:
> > Our current defaults are root:wheel on FreeBSD and macOS, root:root
> > everywhere else.
> > 
> > Looking at what downstream distributions actually do, we can see that
> > these defaults are overriden the vast majority of the time, with a
> > number of variations showing up in the wild:
> > 
> >   * qemu:qemu -> Used by CentOS, Fedora, Gentoo, OpenSUSE, RHEL
> >                  and... As it turns out, our very own spec file :)
> > 
> >   * libvirt-qemu:libvirt-qemu -> Used by Debian.
> > 
> >   * libvirt-qemu:kvm -> Used by Ubuntu.
> > 
> >   * nobody:nobody -> Used by Arch Linux.
> > 
> > Based on the above, we can conclude that qemu:qemu are the preferred
> > credentials to be used when spawning a QEMU process, while our
> > current defaults get very little love.
> > 
> > Changing our defaults aligns with what most downstreams are actually
> > doing, promotes running QEMU under a non-root user - which is a very
> > good idea anyway - and shields random people building libvirt from
> > source from unwittingly running their guests as root.
> 
> While I understand the motivation, this impl is problematic because
> it will guarantee that someone building & installing libvirt from
> source on Debian, Ubuntu and Arch will have a non-functional QEMU
> driver as it will try to use a "qemu:qemu" user/group which does
> not exist on those distros.
> 
> If we want to change this, we must ensure that we honour the distro
> specific user/group names you show above, and fallback to root/root
> for distros we don't know about.

Solid point. I'm not sure we want to bake all those values into our
build system, though...

Perhaps we should go about this a different way, and print a fairly
fat warning in the configure recap when no better option has been
provided by the user and so we end up having to use root:root as a
fallback?

-- 
Andrea Bolognani / Red Hat / Virtualization