Hello Jone,

This config gives me an error with a backtrace:

--8<---------------cut here---------------start------------->8---
In gnu/services/base.scm:
   301:21  1 (file-system->fstab-entry #<<file-system> device: "634a6369-c5a8-4f4c-b3e8-35fb92cf850e" title: uui…>)
In gnu/system/uuid.scm:
    276:2  0 (uuid->string . _)

gnu/system/uuid.scm:276:2: In procedure uuid->string:
Throw to key `match-error' with args `("match" "no matching pattern" ("634a6369-c5a8-4f4c-b3e8-35fb92cf850e"))'.
--8<---------------cut here---------------end--------------->8---

This is fixed by changing:

  "634a6369-c5a8-4f4c-b3e8-35fb92cf850e

to:

  (uuid "634a6369-c5a8-4f4c-b3e8-35fb92cf850e")

Next I get:

--8<---------------cut here---------------start------------->8---
ERROR: In procedure scm-error:
In procedure map: Wrong type argument: (#<<menu-entry> label: "GNU with Linux-Libre 4.15.7 (beta)" device: "two" device-mount-point: "/" linux: #<<file-append> base: #<package linux-libre@4.15.7 gnu/packages/linux.scm:270 1f7f0c0> suffix: ("/" "bzImage")> linux-arguments: ("--root=two" #<gexp (string-append "--system=" #<gexp-input #<derivation /gnu/store/6smdgm944njdvi4vinm27jw428j0l4dn-system.drv => /gnu/store/gsq19cd625bqh4xjmq1srv8b1vjbksig-system 57ae730>:out>) 3a56e40> #<gexp (string-append "--load=" #<gexp-input #<derivation /gnu/store/6smdgm944njdvi4vinm27jw428j0l4dn-system.drv => /gnu/store/gsq19cd625bqh4xjmq1srv8b1vjbksig-system 57ae730>:out> "/boot") 3a56de0>) initrd: #<<file-append> base: #<derivation /gnu/store/25qa7574n3zbrjr78njmbcj085g7d96b-raw-initrd.drv => /gnu/store/nc66z7m1b55ymlcxv9anqpcvxz71dz50-raw-initrd 50ed230> suffix: ("/initrd")>> . #<<menu-entry> label: "Old" device: #f device-mount-point: #f linux: "/boot/vmlinuz-4.14.9-calculate" linux-arguments: ("root=/dev/sda3") initrd: "/boot/initramfs-4.14.9-calculate.img">)
--8<---------------cut here---------------end--------------->8---

This is because ‘menu-entries’ (plural) expects a list of ‘menu-entry’,
not just one ‘menu-entry’.

Once I’ve fixed that, I can build the config with ‘guix system vm’ or
similar.

I’m attaching the corrected version below (I also removed useless
‘use-modules’ lines at the top.)  Let me know if it works for you.

HTH,
Ludo’.