With every new systemd release, we’ve found out that the so-called init system can do a lot more than it was initially designed to, slowly taking over many of the “jobs” of a GNU/Linux operating system’s internal components, and even worse, replacing them completely.
Upstart is a Canonical/Ubuntu project, an event-based replacement for the traditional init daemon that the company used in almost every Ubuntu Linux release. However, starting with the now-deprecated Ubuntu 15.04 (Vivid Vervet) operating system, Canonical replaced the Upstart init system with systemd, making many users angry.
It also looks like Upstart is still being used in Ubuntu as a replacement for the /sbin/init daemon to handle starting of various services and tasks during boot, as well as to stop them during shutdown. For example, Upstart is currently used for the session startup, and Canonical plans, once again, to replace it with systemd.
Submitted by: Arnfried Walbrecht