enable an apache mod via the command line
root@broadside:/home/dev# cd /etc/apache2
root@broadside:/etc/apache2# ls
apache2.conf conf.d envvars magic mods-available mods-enabled ports.conf sites-available sites-enabled ssl
root@broadside:/etc/apache2# ls mods-available/ | grep header
headers.load
root@broadside:/etc/apache2# cp mods-available/headers.load mods-enabled/
root@broadside:/etc/apache2# /etc/init.d/apache2 restart