To quote the Upstart home page:
is an event-based replacement for the
/sbin/initdaemon which handles starting of tasks and services duringboot, stopping them during shutdown and supervising them while the system is running.
One would think that the best place to find the current documentation on Upstart would be its home page and/or the Upstart Wiki. But you would be wrong. The homepage has almost no documentation and the Wiki has ancient documentation (mostly from version 0.3.9 and one page of useless info from 0.5.1while the current version is 0.6.5) with no mention on how to find current documentation.
If you look in /usr/share/doc/upstart* you will find nothing of use.
The secret is man 5 init on an Ubuntu system that has upstart installed (like Ubuntu 9.10). This has some quite good and complete reference info on Upstart.
I have been using forms of Unix for over 30 years (yikes!) and “init” is not what I think of when I think of Upstart. Yes I know its a replacement for init now. But I still don’t think of it the same. If at least the Upstart pages would say “See man 5 init” for details, I might remember…
Anyway, I updated the wiki page to remind me and others that is where to get the latest info…
A good article that is a bit dated, but has more info than I found anywhere else is: