The easy way is to add tvheadend too your /etc/rc.local. The line would look something like: tvheaded -f -u (user to run it as) -g (group).
The other solution would be to create a script like this one in /etc/init.d:
### BEGIN INIT INFO
# Provides: tvheadend
# Required-Start: $remote_fs $syslog userhdhomerun
# Required-Stop: $remote_fs $syslog
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Start tvheadend daemon at boot time
# Description: Enable service provided by tvheadend daemon.
### END INIT INFO
TVHNAME="tvheadend"
TVHBIN="/usr/bin/tvheadend"
TVHUSER="hts"
TVHGROUP="hts"
case "$1" in
start)
echo "Starting tvheadend"
sleep 5
start-stop-daemon --start --user ${TVHUSER} --exec ${TVHBIN} -- \
-u ${TVHUSER} -g ${TVHGROUP} -f -C
;;
stop)
echo "Stopping tvheadend"
start-stop-daemon --stop --quiet --name ${TVHNAME} --signal 2
;;
restart)
echo "Restarting tvheadend"
start-stop-daemon --stop --quiet --name ${TVHNAME} --signal 2
start-stop-daemon --start --user ${TVHUSER} --exec ${TVHBIN} -- \
-u ${TVHUSER} -g ${TVHGROUP} -f -C
;;
*)
echo "Usage: tvheadend {start|stop|restart}"
exit 1
esac
exit 0
Give it the right permissions with chmod 755 and then with the command "insserv nameofyourscript" make it run everytime you boot your server.