Attila Lendvai schreef op vr 25-02-2022 om 21:28 [+0000]:
> is there a way to instruct `guix system vm ...` _not_ to rebuild all the
> dependants, and only replace the Shepherd that is running as the init process?

This can be done by customising the 'shepherd' field of 'shepherd-
configuration', introduced in 95f72dcd7aece05e9252c93bef5a831f96cb5393.

The manual has an example on how to use this:

The following example specifies the Shepherd package for the operating
system:

@lisp
(operating-system
  ;; ...
  (services (append (list openssh-service-type))
            ;; ...
            %desktop-services)
  ;; ...
  ;; Use own Shepherd package.
  (essential-services
   (modify-services (operating-system-default-essential-services
                     this-operating-system)
     (shepherd-root-service-type config => (shepherd-configuration
                                            (inherit config)
                                            (shepherd my-shepherd))))))

Greetings,
Maxime.