The slim package from slackbuilds.org has a broken PAM configuration and fails to start proper desktop sessions with elogind, which results in a broken user experience in modern desktop environments, like you see.
It doesn't have anything to do with starting a dbus session. Elogind runs on the system dbus, which gets started at boot from the rc.messagebus script, and then later on elogind starts with rc.elogind. The missing piece is telling elogind when a user session starts from slim, which is supposed to happen in slim's PAM stack at login.
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This issue with slim has popped up here on the forums a few times recently and last time I looked into it there needs to be changes made to slim's PAM setup to fix the package. It uses some crap config files for PAM that look like they're meant for another distro which do not work on Slackware.
If you want to see slim working better and don't mind changing some config files, the following works (verified from a few minutes of testing):
1. Use the PAM config from XDM for slim by making a copy, naming it to slim, and putting it into the proper directory. As root:
Code:
# cd /etc/pam.d
# mv slim slim-old
# cp xdm slim
Note: This config should work "as-is". The one that slim installs in /etc/pam.d/slim/slim.pam is garbage and can be ignored. Also don't use that /etc/pam.d/slim/ sub-drectory. PAM doesn't seem to find the config file there and needs to be at /etc/pam.d/slim instead. In the above steps, I move this directory out of the way so I can use that filename for slim's PAM config file instead.
2. There's the "slimlock" pam config as well. This I'm not sure on the use of, but its also wrong since it references a PAM config file thats non existent on Slackware. The following steps will grab a copy, edit the line to use slackware's system-auth, and put it in a spot where PAM can find it:
Code:
# cd /etc/pam.d
# mv slimlock slimlock-old
# sed 's/system-local-login/system-auth/g' slimlock-old/slimlock.pam > slimlock
I tried those changes which results in a session started from slim being properly tracked in "loginctl list-sessions", and being able to edit wifi connections in xfce, etc are working.
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These changes should really be made by the package maintainer, to tailor the package to Slackware's PAM setup. Personally I'm not interested in maintaining/updating slim as I already maintain and use the GDM build on slackbuilds.org. Feel free to point the maintainer to this thread though. It could be the case that the maintainer only uses slim for simple window managers without elogind, or the package is not maintained at all and just been that way since PAM was added to Slackware.
Edit: After further poking around with slim, there seems to be other broken things about it, e.g: not being able to "switch user". There's also other things that are off like the docs.slackware.com article talking about changing desktop selection with xwmconfig, but its "F1" that you use instead. Probably best to just use a display manager like xdm or sddm, which has been kept up to date with Slackware.