So I’ve been tearing my hair out for quite a while now after Debian changed from sysv to systemd as the init system.
After some update or other, my laptop’s internal mouse and keyboard would not work under X. In a terminal they worked fine, as did external USB devices. This breakage took a while to track down to Debian having installed systemd automatically. I “fixed” this by reverting to sysv.
However, under sysv init, KDE’s Dolphin could no longer mount devices; permission errors. I tried many solutions to fix this all to no avail (*). Using udiskctrl I could mount devices manually, but that’s a bit of a pain. Clearly I needed to move to systemd, where the permission problems did not exist.
After various online searches I finally hit on the real culprit: I had mounted /var/run and /var/lock as tmpfs to save the SSD on my new laptop, many moons ago. At some point, Debian changed these directories to be symlinks to locations which are already tmpfs-mounts, and hence my local manual configuration overrode those mounts, breaking systemd in various interesting ways.
The following bug-report finally got me on the right tracK:
So I removed the offending lines in /etc/fstab, rebooted, and systemd is happy.
“Failed to get D-Bus connection”
“Failed to get D-Bus connection: No such file or directory”
“systemd laptop keyboard not working”
“systemd-journald: Received SIGTERM from PID 1 (systemd)”
(*)UPDATE: this is a separate issue; yet to be resolved. I thought this worked when I booted under systemd, but it doesn’t.