Book Image

Linux System Programming Techniques

By : Jack-Benny Persson
Book Image

Linux System Programming Techniques

By: Jack-Benny Persson

Overview of this book

Linux is the world's most popular open source operating system (OS). Linux System Programming Techniques will enable you to extend the Linux OS with your own system programs and communicate with other programs on the system. The book begins by exploring the Linux filesystem, its basic commands, built-in manual pages, the GNU compiler collection (GCC), and Linux system calls. You'll then discover how to handle errors in your programs and will learn to catch errors and print relevant information about them. The book takes you through multiple recipes on how to read and write files on the system, using both streams and file descriptors. As you advance, you'll delve into forking, creating zombie processes, and daemons, along with recipes on how to handle daemons using systemd. After this, you'll find out how to create shared libraries and start exploring different types of interprocess communication (IPC). In the later chapters, recipes on how to write programs using POSIX threads and how to debug your programs using the GNU debugger (GDB) and Valgrind will also be covered. By the end of this Linux book, you will be able to develop your own system programs for Linux, including daemons, tools, clients, and filters.
Table of Contents (14 chapters)

Enabling and disabling a service – and starting and stopping it

In the previous recipe, we added our daemon as a service to systemd with a unit file. In this recipe, we'll learn how to enable it, start it, stop it, and disable it. There is a difference between enabling and starting and disabling and stopping a service.

Enabling a service means that it will start automatically when the system boots. Starting a service means that it will start right now, regardless of it being enabled or not. And disabling a service means that it will no longer start when the system boots. Stopping a service stops it right now, regardless of it being enabled or disabled.

Knowing how to do all of this enables you to control the system's services.

Getting ready

For this recipe to work, you'll first need to complete the previous recipe, Writing a unit file for a daemon.

How to do it...

  1. Let's start by checking out the daemon status again. It should be both...