Update documentation for how to enable CUPS

[b90g]

How to file a helpful issue

Qubes OS release

4.2rc3

Brief summary

I am not able to just start the cups service (in fedora38 xfce its not even installed)

maybe after changes discussed in #5179

Steps to reproduce

sudo systemctl status cups

Expected behavior

Active: active (running)

Actual behavior

user@disp9578:~$ sudo systemctl status cups
○ cups.service - CUPS Scheduler
     Loaded: loaded (/lib/systemd/system/cups.service; enabled; preset: enabled)
    Drop-In: /usr/lib/systemd/system/cups.service.d
             └─30_qubes.conf
     Active: inactive (dead)
TriggeredBy: ○ cups.socket
             ○ cups.path
  Condition: start condition failed at Mon 2023-09-11 11:19:03 CEST; 1s ago
             └─ ConditionPathExists=/var/run/qubes-service/cups was not met
       Docs: man:cupsd(8)

Sep 11 11:09:46 disp9578 systemd[1]: cups.service - CUPS Scheduler was skipped because of an unmet condition check (ConditionPathExists=/var/run/qubes-service/cups).
Sep 11 11:19:03 disp9578 systemd[1]: cups.service - CUPS Scheduler was skipped because of an unmet condition check (ConditionPathExists=/var/run/qubes-service/cups).

Workarround

user@disp9578:~$ sudo mkdir /var/run/qubes-service/cups
user@disp9578:~$ sudo systemctl start cups
user@disp9578:~$ sudo systemctl status cups
● cups.service - CUPS Scheduler
     Loaded: loaded (/lib/systemd/system/cups.service; enabled; preset: enabled)
    Drop-In: /usr/lib/systemd/system/cups.service.d
             └─30_qubes.conf
     Active: active (running) since Mon 2023-09-11 11:20:11 CEST; 2s ago
TriggeredBy: ● cups.socket
             ○ cups.path
       Docs: man:cupsd(8)
    Process: 4243 ExecStartPost=/usr/lib/qubes/init/control-printer-icon.sh (code=exited, status=0/SUCCESS)
   Main PID: 4242 (cupsd)
     Status: "Scheduler is running..."
      Tasks: 1 (limit: 4617)
     Memory: 2.0M
        CPU: 28ms
     CGroup: /system.slice/cups.service
             └─4242 /usr/sbin/cupsd -l

Sep 11 11:20:11 disp9578 systemd[1]: Starting cups.service - CUPS Scheduler...
Sep 11 11:20:11 disp9578 systemd[1]: Started cups.service - CUPS Scheduler.

[DemiMarie]

This is by design. To enable CUPS, use qvm-service QUBENAME cups on in dom0.

Closing as “not a bug” (the reported behavior is not a bug and is already working as intended).

[nereocystis]

The behavior has changed from 4.1 to 4.2. In 4.1, my templates and qubes worked with cups on HP. In 4.2, the printers disappeared without notice. If this behavior is expected, then the upgrade documents need to be changed to reflect that.

[marmarek]

The comment https://github.com/QubesOS/qubes-issues/issues/8508#issuecomment-1714565636 is accurate, it is expected behavior.

[q4747]

See related discussion/guide here: https://forum.qubes-os.org/t/how-to-get-a-usb-mfp-printer-scanner-working-in-r4-2/24520