without writing complex initialization scripts in the /etc/rc.d/init.d/ directory and creating symbolic links.
In my opinion, it shouldn't be too difficult.
The script, after all, doesn't need to be complex.
Just create your script under "/etc/init.d/".
Make sure it works when called manually.
Give it the same owner/permissions as other "init.d" scripts.
On my system, this would go like:
chown root:root myscript (skip if already root)
chmod u=rwx,g=r,o=r myscript
Finally issue "ln -s /etc/init.d/myscript /etc/rc3.d/S##myscript". Replace ## with two numbers (00...99) to control when exactly your script runs. Within the same runlevel, scripts with smaller numbers get executed before.