upstart typically controls two types of processes:
- programs that run once to process the event
- demons that are durable and provide a service to something else.
Daemons usually provide a signal handler for the signal SIGHUPto ask the daemon to re-read and re-analyze their configuration files. ( SIGHUPis a hang-up signal, more relevant for terminals that can appear and arrive when telephone lines or SSH protocols are connected or disconnected. For programs that do not have terminals, it makes no sense to hang up their terminal, so the signal will not be sent to a daemon, except under the action of a system administrator.)
, , SIGHUP, upstart reload service . ( - , , - - .)