If the root partition is not encrypted (and not RAID or anything like
that), you don’t need to declare a “mapped device” for it. All you need
is to declare a file system in the ‘file-systems’ field.
HTH!
Yes, it did help ! In fact I was able to start the process
BUT
it didn' t end correctly :-/
Installing for i386-pc platform
grub-install: error: cannot find a GRUB drive for /dev/sd1. Check your device.map.
guix-system: failed to install GRUB on device '/dev/sd1'
As far as I understand my platform should be x86_64