Well, I think a recent change that happened, or else I only recently noticed it, was that when I use Devuan ceres with lightdm (instead of slim) with xfce4, the user cannot effectively select “Restart” or “Shutdown” from the menu.
The options may nor may not be enabled, but selecting either of them just return the user to the login screen.
For some random reason I was searching for “consolekit” on the Devuan forum and stumbled across an interesting title: HOWTO: lightdm (with libpam-elogind) + xfce4 (ASCII/Stable) / Documentation / Dev1 Galaxy Forum
After adapting the instructions for ceres (unstable) release, I am pleased to announce the successful results! The steps that I took are the following. Observe that they are briefer than the instructions provided by the source. Trying to add or remove other packages than the two listed here on my system caused apt-get to want to remove some crazy sets of packages which I obviously wanted to keep
sudo apt-get install --no-install-recommends libpolkit-gobject-elogind-1-0 policykit-1 lightdm lightdm-gtk-greeter # and adjust pam: sed -i -r -e '/session\s+optional\s+pam_systemd.so/s/systemd/elogind/;' /etc/pam.d/lightdm-greeter
I chose to reboot to ensure lightdm inherited the new pam settings. And, then my user could shut down from the user session! It’s the little things, isn’t it…