@ianabc Had a bit more time to look into this now. You have missed one important point here. You need to manually create a new TaskType (web UI -> main menu -> TaskTypes -> Create New Task Type) and name that trusty-install - exactly the name of the task that is used in lib/hooks/boottask.hook.php (line 73). As soon as you’ve created this task type you should see it in Host -> Basic Tasks (or Host -> Basic Tasks -> Advanced Tasks if you’ve checked the “Is Advanced” checkbox when creating it!).
Now you can schedule this task type for any client or group and when it boots up it uses the arguments you set in lib/hooks/boottask.hook.php (line 83 to 93). But only if the names match. So if you name your new task bababoo you need to have that in your lib/hooks/boottask.hook.php line 73 as well.