Book Image

Linux Shell Scripting Essentials

By : Sinny Kumari, Khem Raj
Book Image

Linux Shell Scripting Essentials

By: Sinny Kumari, Khem Raj

Overview of this book

Table of Contents (15 chapters)
Linux Shell Scripting Essentials
About the Author
About the Reviewers


Nowadays, most of the Linux distribution systems such as Fedora, Ubuntu, Arch Linux, Debian, openSUSE, and so on, have switched from init to systemd. systemd is the first process that gets started after system boot-up with PID 1. It controls and manages other processes that should be started after the system boot-up. It is also known as basic building block for an operating system. To learn about an init-based system, refer to the Wikipedia link at

systemd units

systemd has several units, each containing a configuration file with information about a service, socket, device, mount point, swap file or partition, start-up target, and so on.

The following table explains some of unit files:

Unit type

File extension


Service unit


A system service

Device unit


A device file recognized by kernel

Mount unit


A file system mount point

Timer unit


A systemd timer

Swap unit


A swap file