Linux Shell Scripting Cookbook - Third Edition

Getting ready

The first step is to determine whether your system is using the SysV init calls, systemd, or upstart.

Linux/Unix systems must have an initialization process running as PID 1. This process executes a fork and exec to start every other process. The ps command may tell you which initialization process is running:

    $ ps -p 1 -o cmd
    /lib/system/systemd

In the previous example, the system is definitely running systemd. However, on some distributions, the SysV init program is sym-linked to the actual init process, and ps will always show /sbin/init, whether it's SysV init, upstart, or systemd that's actually being used:

    $ ps -p 1 -o cmd
    /sbin/init

The ps and grep commands give more clues:

    $ ps -eaf | grep upstart

Alternatively, ...