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)

Getting to know systemd

In this recipe, we'll explore what systemd is, how it handles the system, and all of the system's services.

Historically, Linux has been managed with several smaller pieces. For example, init was the first process on the system, which started other processes and daemons to bring up the system. System daemons were handled by shell scripts, also called init scripts. Logging was done either by the daemon itself via files or syslog. Networking was also handled by multiple scripts (and still is in some Linux distributions).

Nowadays, though, the entire system is handled by systemd. For example, the first process on the system is now systemd (which we have seen in previous chapters). Daemons are handled by something called unit files, which create a unified way of controlling daemons on the system. Logging is handled by journald, systemd's logging daemon. But do note that syslog is still used by many daemons to do extra logging. Later in this...