No logs are written to /var/log
Ok, I found solution somewhere else:
sudo apt-get install --reinstall rsyslog
It seems rsyslog was removed itself at some point.
have you started/restarted the systemlogs deamon?
sudo service rsyslog start
or
sudo service rsyslog restart
this should work. This problem came for me also, i restarted this deamon, now its working fine.