I was doing a system update using
zypper update
After a while the screen was filled with this message
failed to start system logging service.
and the system was not responding. I had to shutdown it by holding the power button.
then I started the machine again, and selected to boot suse.
Then I saw the fancy boot animation(some shiny big dots gathering to the center of the screen), then the screen just turned black and the monitor sayed "no signal".
then I tried to boot into suse failsafe mode, which was fine.
how can I investigate into this problem?