how to disable upstart services in ubuntu

ubuntu 11.04 or later:

echo manual > /etc/init/<service>.override

ubuntu 10.04:

echo start on never > /etc/init/<service>.conf

the last start on in the file wins, but this solution assumes that there is no event called never. better:

start on runlevel [!0123456]

note the ! inverts the sense of the match.