Trying to get rid of index.php from address on my ubuntu system

ohk so got to your terminal and sudo nano /etc/apache2/apache2.conf. edit the file and change all AllowOverride None to AllowOverride All.
After that you need to enable mod rewrite by typing sudo a2enmod rewrite, after which you restart the server using sudo /etc/init.d/apache2 restart.

I think that should do the trick. If it doesnt youll have to look inside your .htaccess file.