Thank you:
I checked the following:
- HOST system
$ groups
sys network power vboxusers lp wheel myname
$ grep '^vboxusers:.*$' /etc/group | cut -d: -f4
myname
# IF NOT: sudo gpasswd -a $USER vboxusers
- GUEST system
$ systemctl status vboxservice
Active, running!
$ groups
sys network power vboxsf lp wheel myname
$ grep '^vboxsf:.*$' /etc/group | cut -d: -f4
myname
# IF NOT: sudo gpasswd -a $USER vboxsf
So I think, all conditions should be fulfilled.
After booting the GUEST using kernel 6.9, a message shows up:
VBoxClient: the VirtualBox kernel service is not running. Exiting.
I switched the GUEST to kernel 5.15 (same as the HOST) but the same message is shown.
Running kernel 5.15 I re-installed virtualbox-guest-utils and fired:
$ sudo bash VBoxLinuxAdditions.run
Booting brings the same message.
Now what?