bug#23838: Guix on Debian 8.3 'guix system vm ...' -> "ERROR: qemu failed "qemu-system-x86_64"

[Ludovic Courtès]

Hi!

myglc2 <address@hidden> skribis:

> The following derivations will be built:
>    /gnu/store/jz6mlhlz7f5sp4g93spac69bxfjpjbqg-run-vm.sh.drv
>    /gnu/store/5f6zfsx0fa0bzkl4ynqb1lf5pk3m4rfs-qemu-image.drv
> warning: failed to install locale: Invalid argument
> building path(s) `/gnu/store/nbppjjb2kkb17nr8jqas7hchkg669nv9-qemu-image'
> Formatting 'image.qcow2', fmt=qcow2 size=31457280 encryption=off 
> cluster_size=65536 lazy_refcounts=off refcount_bits=16
> Could not access KVM kernel module: Permission denied
> failed to initialize KVM: Permission denied

Please make sure the guixbuild* user accounts have write permission for
/dev/kvm.

Usually, /dev/kvm is has “kvm” as its group and is group-writable.  So
all you need is to add the guixbuild* users to the “kvm” group.

The manual mentions this pitfall (info "(guix) Invoking guix system")
but I guess it’s easily missed.

Thanks,
Ludo’.