Comment 11 for bug 1598300

I have done some tests and have found a solution. Please try it out.

Edit the file (with sudo):

/lib/systemd/system/cups.socket

adding a line

ListenStream=631

in the "[Socket]" section. The file should look like this then:

----------
[Unit]
Description=CUPS Scheduler

[Socket]
ListenStream=/var/run/cups/cups.sock
ListenStream=631

[Install]
WantedBy=sockets.target
----------

Now make sure that this does not produce any editor backup files, like /lib/systemd/system/cups.socket~ or /lib/systemd/system/cups.socket.backup. Remove such files now.

Now restart systemd with the command

sudo systemctl daemon-reload

Now systemd does not only restart CUPS via the domain socket but also via port 631, meaning that it also gets started when trying to access via the web interface (or any other application which accesses only via port 631).

Please try it out.

If you do not want to wait everytime until CUPS stops by itself for doing the tests, you can stop it with

sudo systemctl stop cups