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.