There is a script located at /etc/rc.local that runs when the server starts up.

By default, all the script has in it is this:

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

exit 0

Just add anything before the “exit 0”.