Re: unbound variable in attempt to install "lightdm"

[Felix Lechner via <help-guix@gnu.org>]

Hi Gottfried,

On Fri, May 12, 2023 at 8:50 AM Gottfried <gottfried@posteo.de> wrote:
>
> So can I have both installed?

It's possible to have the packages for two display managers installed
at the same time, but the system can only be configured to use one at
any given time. Guix services do both: They install the package and
cause the display manager to control your graphical devices. That's
why you can only use one Guix service at a time.

I believe that %desktop-services already configures a gdm-service-type
for you because that's the standard graphical login manager we provide
in Guix. That's why you should drop gdm-service-type from
%desktop-services when adding lightdm-service-type. I believe that is
the source of the error message you saw.

I do not use %desktop-services personally, but also drop some services
from %base-services. You can see how I did that here. [1] You
basically have to replace the expression

    %desktop-services

in your list of services with something like

    (modify-services %desktop-services
        (delete gdm-service-type))

At first sight, it does not look very intuitive, but you can make
sense of it with a functional programming perspective. (Functional
programming is a reason why many of us prefer Guix over other
operating systems.) When the expression inside outermost parentheses
is executed, you get a modified %desktop-services without
gdm-service-type. I believe that's what you want and need.

I am kind of new here, however, and am happy to defer to more
experienced Guix users and developers.

Kind regards
Felix

[1] https://codeberg.org/lechner/system-config/commit/42ecb69ff9ca0af7739e3c51a5d368aaa6e6d218