In Linux and other Unix-like operating systems, the initialization process is the first process executed by the kernel at boot time, with a process ID (PID) of 1, and operates in the background until the system is shut down. The init process is responsible for starting all other Linux processes, such as daemons, services, and background processes, making it the parent of all other processes on the system.
Over the years, various init systems have emerged in major Linux distributions. Some of the notable init systems are:
1. System V Init:
System V (SysV) is a mature and popular init scheme on Unix-like operating systems. It is the parent of all processes on a Unix/Linux system.
2. SystemD:
SystemD is a relatively new init scheme that has become the dominant init system in the Linux ecosystem. It is widely adopted by major Linux distributions as the default init system.
3. OpenRC:
OpenRC is a dependency-based init scheme that offers some improvements to SysV init. It is actively maintained and is the default init system for Gentoo Linux.
4. runit:
Runit is a cross-platform init system that provides service supervision and is used in Void Linux as the default init system.
5. s6:
s6 is a set of tools for UNIX, designed for process supervision. It is actively developed and popular in embedded systems and container environments.
6. Dinit:
Dinit is a modern, dependency-based service manager and init system that aims to provide a minimalist alternative to systemd. It is actively developed and gaining traction in the community.
Overall, while systemd is the dominant init system in major distributions, there are alternative init systems like OpenRC, runit, s6, and Dinit that cater to users who prefer simpler and more Unix-philosophy-aligned approaches.
