Previous to systemd-240, pam_systemd would set DBUS_SESSION_BUS_ADDRESS $XDG_RUNTIME_DIR/bus (aka the "user" bus). After systemd-240, this is no longer set; instead, it relies on the behavior of recent versions of libdbus to connect to this address automatically if DBUS_SESSION_BUS_ADDRESS is unset. The /etc/X11/xinit/xinitrc/80-dbus script is not equipped to deal with this, and instead launches a brand new dbus-daemon if DBUS_SESSION_BUS_ADDRESS is unset. 80-dbus should be modified to not do this, or the script should be dropped entirely.
systemd behavior change: https://github.com/systemd/systemd/commit/2b2b7228bffef626fe8e9f131095995f3d50ee3b
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=55b9c69178b4518b06b29c3f156c2f1e33211224 commit 55b9c69178b4518b06b29c3f156c2f1e33211224 Author: Mike Gilbert <floppym@gentoo.org> AuthorDate: 2019-01-24 14:47:16 +0000 Commit: Mike Gilbert <floppym@gentoo.org> CommitDate: 2019-01-24 14:47:16 +0000 sys-apps/systemd: backports for 240 based on v240-stable branch Bug: https://bugs.gentoo.org/674520 Bug: https://bugs.gentoo.org/674292 Bug: https://bugs.gentoo.org/674152 Package-Manager: Portage-2.3.56_p3, Repoman-2.3.12_p50 Signed-off-by: Mike Gilbert <floppym@gentoo.org> sys-apps/systemd/Manifest | 1 + sys-apps/systemd/systemd-240-r4.ebuild | 457 +++++++++++++++++++++++++++++++++ 2 files changed, 458 insertions(+)
I believe systemd upstream reverted the behavior at some point.