This may help someone so I am jotting down an issue I had. On some Linux flavors you may see the Virtualbox Guest additions shared folders not auto mounting on your desktop. I have seen this before but recently this was on Linux Lite for me.
The issue is that systemd is not starting the vbox-service. I am not sure if this is the best fix but for now I removed systemd-timesyncd.service from the Conflicts section in the unit file as shown below.
Also note that I completely purged the v5.x guest additions that came standard and installed v6 from the guest additions ISO.
# pwd /lib/systemd/system # diff vboxadd-service.service /tmp/vboxadd-service.service 6c6 < Conflicts=shutdown.target --- > Conflicts=shutdown.target systemd-timesyncd.service
Above option means the unit file change will be reversed when you update the guest additions. So another option for now is to disable systemd-timesyncd.service. Not sure if that breaks the guests time sync but sounds like virtualbox guest additions sync time with the host anyhow.
# systemctl disable systemd-timesyncd.service Removed /etc/systemd/system/sysinit.target.wants/systemd-timesyncd.service.