@shegeley this is off the top of my head, but the guix-service-type guix is only used as the guix-daemon guix and maybe the /run/current-system/bin/guix . Your user's guix, which unless you have a very weird setup is what you'll be running, comes from your .config/guix/channels.scm at the time you last `guix pull`-ed. The guix that you run determines which package definitions you are using.

So file:// might be the cleanest way.