Mosquitto MQTT on Raspberry Pi fails on startup

On my Raspberry Pi I want to use the Mosquitto MQTT broker, but if fails to start up as a serivce.

sudo service mosquitto status

just gives me

FAIL mosquitto is not running ... failed! 

The problem was, that the log file was not as expected in /var/log/mosquitto/mosquitto.log because I use tmpfs for /var/log.

To fix the problem, I added these lines in /etc/init.d/mosquitto in the start section:

mkdir /var/log/mosquitto
mkdir /var/log/mosquitto.log