If your ApacheDS is misbehaving — doesn’t start or stop — it most probably has to do with its .pid file that’s lying around because of an unclean shutdown. In which case you just need to delete it manually, and things will get back to normal.
In the CentOS 6 machine that I work on, the file is created in /var/lib/apacheds-2.0.0-M7/default/run by the name of apacheds-default.pid. On Ubuntu machines, this could be in /var/run.
Once the file is removed, simply run the /etc/init.d/apacheds start command to get it going!