Init Systems

Init is the first process that is executed once the Kernel loads.

Until the 2010's, Linux was using the BSD-style SysVinit
There is a religious war of people who hate systemd and the inventor of it, and prefer either OpenRC or SysVinit over systemd

List of Inity Systems

systemd
- A modern SysV-style init and rc replacement for Linux systems
- Solves many issues with the original SysVinit
- I am a big fan of systemd and I never want to return to sysVinit
- History
  - Development was lead by Red Hat and was the idea of Lennart Poettering
  - 2010 first release
  - 2019 fully adopted by most distributions
- Documentation
- Good article: The Biggest Myths
SysVinit
- init as per AT&T UNIX System V
- Is a collection of System V-style init programs
- 1983 first release
OpenRC
- a dependency-based init system that is compatible with SysVinit
- Gentoo and BSD usage mostly
- 2015 first release
runit
- runit is a daemontools-inspired process supervision suite
BSD init (init as per BSD / Research UNIX)
- Predates SysVinit
- 1982 first release
Upstart
- Abandoned by Canonical in 2014 in lieu of systemd