To start icecast at system boot, customize 
%%PREFIX%%/etc/icecast.xml.sample to your environment and add:

icecast_enable="YES"

to /etc/rc.conf. See the icecast -h command for optional additional
flags. To specify an alternative config file for example add:

icecast_flags="-c /path/to/your/configuration.xml"

**********************************************************************
**  Make sure the <changeowner> section in your configuration file  **
**     is NOT commented out. Icecast will refuse to run as root.    **
**                                                                  ** 
** Also make sure that the user you choose is able to write to your **
**  configured log directory, otherwise icecast will refuse to run. **
**********************************************************************