Summary: 
The instructions to build a virtual machine uses /dev/sda* devices for harddrive which are then referenced in /etc/config.scm. 
The instructions to run the vm uses /dev/vda* devices for harddrive 
This causes "sudo guix system reconfigure /etc/config.scm" to fail with... 
guix system: error: '/gnu/store/q6q99b1r6wxzdxh3a19z2ng88sfpdryn-grub-2.04/sbin/grub-install --no-floppy --target=i386-pc --boot-directory //boot /dev/sda' exited with status 1; output follows: 
Installing for i386-pc platform. 
/gnu/store/q6q99b1r6wxzdxh3a19z2ng88sfpdryn-grub-2.04/sbin/grub-install: error: cannot find a GRUB drive for /dev/sda. Check your device.map. 



Specifics: 


For at least quemu-system-x86_64 version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.23) 




<https://guix.gnu.org/manual/en/guix.html#Installing-Guix-in-a-VM> creates a disk layout with /dev/sda 

$ qemu-system-x86_64 -m 1024 -smp 1 -enable-kvm \
    -nic user,model=virtio-net-pci -boot menu=on,order=d \
    -drive file=guix-system.img \
    -drive media=cdrom,file=guix-system-install-1.1.0. system .iso 

while <https://guix.gnu.org/manual/en/guix.html#Running-Guix-in-a-VM> reflects the disk layout as /dev/vda 
$ qemu-system-x86_64 \
     -nic user,model=virtio-net-pci \
     -enable-kvm -m 1024 \
     -device virtio-blk,drive=myhd \
     -drive if=none,file=/tmp/qemu-image,id=myhd 

Recommendation.  Change the install directions to use virtio-blk... 
$ qemu-system-x86_64 -m 1024 -smp 1 -enable-kvm \
    -nic user,model=virtio-net-pci -boot menu=on,order=d \ 
-device virtio-blk,drive=myhd \ 
-drive if=none,file=guix-system.img,id=myhd \
    -drive media=cdrom,file=guix-system-install-1.1.0. system .iso