Upstart

• upstart was designed to address System V init’s shortcomings and to provide a more robust system for managing services.

• upstart is event-driven, its constantly monitoring the system for certain events to occur, and when they do, upstart can be configured to take action based on those events.

• some examples are a system startup, system shutdown, Ctrl-Atl-Del, runlevel changing or a script starting or stopping.

• If you reenacted the last example with Upstart you could create a upstart script that is triggered when a network cable is plugged in and would restart networking for you. you could then configure any services that require network connection to be triggered whenever networking services started successfully.

• upstart doesn’t completely replace system v init, at least when it comes to services on the system. upstart does replace the functionality of init and the /etc/inittab file, and it manages changes to runlevels, system start-up and shutdown, and console ttys.

• more and more functionality is being ported to upstart scripts, but you will still find some of the standard init scripts in /etc/init.d and all of the standard symlinks in /etc/rc*.d. the difference is that upstart now starts and stops services when runlevels change. upstart scripts reside in /etc/init and have different syntax from init scripts since they aren’t shell scripts upstart treats lines that being with # as comments, like most scripts and configuration files