Comment 17 for bug 934291

I've been investigating this issue recently and can confirm that, while this is not an issue in my Fedora machine with the very same version of cups, cups-pk-helper and gnome-control-center installed, it is still present in Ubuntu, due to what I believe it might be a bug in the way CUPS is being packaged by debian (thus Ubuntu would have inherited the bug). Thus it's probably a bug in Debian as well.

Long story short, while Fedora configures "root" to be part of CUPS system administration group, Debian/Ubuntu does not do that and instead defines "lpadmin" as the only member of that group. Now, because gnome-control-center actually relies in cups-pk-helper to cancel jobs, CUPS won't allow doing that in ubuntu because neither the owner of the job (cups-pk-helper runs as root, not as the username originating the cancel request from g-c-c) nor an user belonging to SystemGroup is requesting such an operation. As a result, the operation is not cancelled.

You can see a more detailed explanation here: https://bugzilla.gnome.org/show_bug.cgi?id=669679#c23

I fixed this locally by changing the debian/rules so that I pass "--with-system-groups='lpadmin root'" to dh_auto_configure, instead of simply passing 'lpadmin' and that works for me. I think it's worth reporting this to debian, but it's unclear to me how to do so, so I thought I would report it here for now, in case someone could lend a hand with it.

Thoughts?

PS: A temporary fix for users facing this problem, better than setting JobsPrivateValues to 'none', would be to simply edit /etc/cups/cups-files.conf and manually add 'root' to SystemGroup