The history of Linux init systems

So, what is an init system? Well, init is short for initialization. An init system, then, initializes the operating system upon bootup. After the bootup has completed, the init system will continue working, managing system processes and services. Each system process is assigned a process ID number, or PID. The init process is always PID 1, and every other process that gets started on the system is either a child or a grandchild of the init process.

For many years, the SysV Init system was the primary init system for Linux-based operating systems (SysV is short for System 5. The V is the Roman numeral for 5). SysV init was originally developed by Bell Labs engineers for the Unix operating system, all the way back in the early 1970s. (At that time, I was a young pup in junior high school, and I still had a full head of hair.)

Note

There are actually a few more Linux init systems besides the ones that I'm mentioning here. But these were the most commonly used ones in the pre-systemd days.

SysV init worked well in its day, but it was never perfect. Nowadays, with new high-performance hardware, SysV init has shown both its age and its deficiencies. The first attempt to come up with something better occurred in July 2009, when Ubuntu engineers released the first version of the upstart init system. Although it was better than SysV, it still had its share of problems, especially the early versions which were quite buggy.