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

On Tue, Mar 26, 2019 at 01:20:46PM +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. Or possibly we can fallback to nobody or similar that is used by every distro. That way we would not use root:root for unknown distros as well.