This looks like the problem I have in Lubuntu 18.04 (but only in systems upgraded from 16.04 - new installs seem fine).
But I can't find the magic "Policykit Authentication Agent" tickbox in Lubuntu: where is it hiding? -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to policykit-1 in Ubuntu. https://bugs.launchpad.net/bugs/976638 Title: pkexec does not find any authentication agent Status in PolicyKit: Unknown Status in policykit-1 package in Ubuntu: Triaged Bug description: I am using xubuntu, but I am pretty sure that other variants are affected too. My problem started with being unable to start synaptic from the menu. So far, I have found out that synaptic is started with pkexec. When I test starting pkexec /usr/sbin/synaptic in a terminal, it asks for the password in text mode. With another test pkexec --disable-internal-agent /usr/sbin/synaptic in the terminal, it says it has not found any authentication agent. I have two AMD64 PC's and a i386 laptop. The problem occurs on one of the PC's and the laptop. Comparing the /etc directory trees of the PC's showed many differences, but I could not find anything suspicious about the polycikit configuration. For the moment, using gksu instead of pkexec is a workaround. Thanks and Regards, Markus ProblemType: Bug DistroRelease: Ubuntu 12.04 Package: policykit-1 0.104-1 ProcVersionSignature: Ubuntu 3.2.0-22.35-generic 3.2.14 Uname: Linux 3.2.0-22-generic x86_64 ApportVersion: 2.0-0ubuntu4 Architecture: amd64 Date: Sun Apr 8 17:05:34 2012 InstallationMedia: Xubuntu 12.04 LTS "Precise Pangolin" - Beta amd64 (20120330) ProcEnviron: LANGUAGE=de_DE:en TERM=xterm PATH=(custom, no user) LANG=de_DE.UTF-8 SHELL=/bin/bash SourcePackage: policykit-1 UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/policykit-1/+bug/976638/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp