Roy Lemmon 写道：
> Sorry but it's been a long day ...

Here too :-)

> I have to specify the nfs package don't I ?

The ‘NFS package’ in

  (file-append nfs-utils "/sbin/mount.nfs")

is nfs-utils, which is a variable defined in the (gnu packages 
nfs) Guile module.

As you note, modules need to be imported first, which is what

> (use-modules (gnu packages nfs))
> (use-service-modules desktop networking ssh xorg mail)

does.  This is the correct variant for your use case: you care 
only about the package which provides mount.nfs to clients, not 
about the server which is what (gnu services nfs) provides.

Aside: the above snippet is completely equivalent to both:

  (use-modules (gnu packages nfs))
  (use-modules (gnu services desktop)
               (gnu services networking)
               (gnu services ssh)
               (gnu services xorg)
               (gnu services mail))

and

  (use-package-modules nfs)
  (use-service-modules desktop networking ssh xorg mail)

USE-{PACKAGE,SERVICE}-MODULES is Guix-specific syntactic sugar 
that saves a lot of space and typing when you're importing many 
package & service modules, as most people do.

Kind regards,

T G-R