Peter,

Peter 写道：
> Greetings! This is my first post. I hope I'm doing it right, and 
> please forgive me if I'm not.

Welcome!  You absolutely are.

> http//:localhost:631 brings up a CUPS interface, but produces an 
> error
> message: "The web interface is currently disabled. Run "cupsctl
> WebInterface=yes" to enable it."

Ah, that wouldn't work anyway: Guix uses read-only configuration 
files.

  $ sudo cupsctl WebInterface=yes
  Password for root on localhost? ***
  cupsctl: Internal Server Error

> I try that but "command not found".

Aside from it not working, you can make cupsctl (along with the 
other cups commands like lp) available for your user with

  $ guix install cups

or for all users by adding it to the (packages …) field in your 
system configuration.

> Commands I have used like 'systemctl start cups.service' etc
> don't work on Guix either. Is there a Guix equivalent?

Guix doesn't have systemd.  The equivalent service manager is the 
GNU Shepherd:

  $ sudo herd restart cups

> Attempts to enable the Web interface via the config.scm (GNU 
> Guix
> Reference Manual 10.8.7) have also failed.

Now that's odd, because it definitely should.  Could you edit your 
system configuration to read:

     (service cups-service-type
              (cups-configuration
                (web-interface? #t)))

and then apply it by running:

  $ sudo guix system reconfigure [your system .scm]
  $ sudo herd restart cups

and confirm that you still get the same error?

> This ought to be encouraging, but when I attempt to print a 
> working
> text document (e.g. via Gedit) although the printer is listed 
> (along
> with IP address and all usual data) it says "Processing - Not
> connected?", despite the system clearly knowing the address etc.

Yeah, this should work even without a Web interface and with zero 
configuration.  Or so I thought…

Are you a member of the ‘lp’ group?  IIRC printing is only allowed 
to its members.  Try:

    (supplementary-groups
     '("wheel" "lp" "netdev" "audio" "video")))

> I set the printer up normally in Gnome Print Settings, but if I 
> look
> at the View Print Queue, it says "Document Print Status: 
> Processing -
> Not connected?". If I go into Server Settings to check the 
> 'Publish
> shared printers connected to this system' setting the 
> troubleshooter
> recommended, I get "CUPS server error: There was an error during 
> CUPS
> operation: 'Failed to set settings'". Troubleshooting's final 
> verdict
> is "There is no obvious solution to this problem."

Heh :-)

As you've probably guessed by now this is due to the read-only 
configuration file.  Only Guix can change CUPS settings through 
your cups-service-type; not any other helpful programmes.

However, ‘Publish shared printers’ shouldn't need to be on to 
print from the local host.  It controls whether known printers are 
further advertised to others over DNS-SD.  The upstream Boolean 
‘Browsing’ (exposed by Guix as cups-configuration's ‘browsing?’) 
is exceptionally poorly named in this regard.

> I'm foxed, and frustrated, and as a desperate work-round I have 
> to ssh
> the file to another machine to be printed. By the way, I have
> successfully set up printing for MacOS, nixOS, Debian, and Arch, 
> but
> GUIX (alone) fails to find the printer, except via the Brother
> utility.

Thanks for so clearly describing your problem and attempted 
solutions.  Let's hope we can unfox you and get you hooked.

Kind regards,

T G-R