[CentOS] dbus/systemd failure on startup (CentOS 7.7)

Wed Jan 22 16:15:24 UTC 2020
James Pearson <james-p at moving-picture.com>

We are seeing a problem that occurs ~5% of the time when rebooting 
CentOS 7.7 where systemd gets a 'Connection timed out' to D-Bus just 
after the D-Bus service starts - from 'journalctl -x' :

...
Jan 21 16:09:59 linux7-7.mpc.local systemd[1]: Started D-Bus System 
Message Bus.
-- Subject: Unit dbus.service has finished start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit dbus.service has finished starting up.
--
-- The start-up result is done.
Jan 21 16:10:24 linux7-7.mpc.local systemd[1]: Failed to register match 
for Disconnected message: Connection timed out
Jan 21 16:10:24 linux7-7.mpc.local systemd[1]: Failed to initialize 
D-Bus connection: Connection timed out
...

This then has a knock-on effect that causes other services to fail - e.g.

-- Unit gdm.service has begun starting up.
Jan 21 16:10:39 linux7-7.mpc.local dbus[817]: [system] Activating 
systemd to hand-off: service name='org.freedesktop.login1' 
unit='dbus-org.freedesktop.login1.service'
Jan 21 16:10:50 linux7-7.mpc.local dbus[817]: [system] Failed to 
activate service 'org.freedesktop.systemd1': timed out
Jan 21 16:10:50 linux7-7.mpc.local systemd-logind[1221]: Failed to 
enable subscription: Failed to activate service 
'org.freedesktop.systemd1': timed out
Jan 21 16:10:50 linux7-7.mpc.local systemd-logind[1221]: Failed to fully 
start up daemon: Connection timed out
Jan 21 16:10:50 linux7-7.mpc.local systemd[1]: systemd-logind.service: 
main process exited, code=exited, status=1/FAILURE
Jan 21 16:10:50 linux7-7.mpc.local systemd[1]: Failed to start Login 
Service.
-- Subject: Unit systemd-logind.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit systemd-logind.service has failed.
--
-- The result is failed.

Whatever the issue is, it appears that polkit might be involved - if we 
restart the polkit service, things appear to return to normal (e.g. gdm 
starts up etc)

We can't find any similar reports of this happening elsewhere with 
CentOS 7.7 - but we were wondering if anyone else had come across a 
problem like this?

Thanks

James Pearson