Linux Daemons: Complete Tutorial Series for System Programmers

Linux system programming — June 7, 2026 · 0 Comment

 

Linux Daemons: Complete Tutorial Series for System Programmers

Linux Daemons Complete Tutorial Series | EmbeddedPathashala
📄 7 HTML Files
💻 14+ Code Examples
🎯 42 Interview Questions
🐧 Linux Systems Programming

What Is This Chapter About?

Chapter 37 of The Linux Programming Interface covers daemon processes — long-running background services that are the backbone of every Linux system. You will learn what daemons are, how to create them correctly using the standard 7-step process, how to write robust daemons that handle signals and avoid resource leaks, and how to use the syslog system for daemon logging.

Topics Covered

Daemon Definition fork() & setsid() Double Fork becomeDaemon() SIGTERM Handler SIGHUP Config Reload PID Lock File Memory Leak Prevention syslog Architecture openlog() / syslog() setlogmask() /etc/syslog.conf Facility & Priority Remote Logging

1
Daemon Overview — What Is a Daemon?
Definition & Characteristics Real-world Examples Kernel Thread Daemons Daemon vs Regular Process No Controlling Terminal

2 Code Examples  |  7 Interview Questions

2
Creating a Daemon — The 7-Step Process
fork() & _exit() setsid() Double Fork umask(0) chdir(“/”) Close FDs /dev/null Redirect becomeDaemon()

2 Code Examples  |  7 Interview Questions

3
Guidelines for Writing Robust Daemons
SIGTERM Handling 5-Second Shutdown Window Memory & FD Leak Prevention Single Instance (PID File) fcntl() Lock

2 Code Examples  |  5 Interview Questions

4
Using SIGHUP to Reinitialize a Daemon
SIGHUP Meaning for Daemons Config File Reload Signal Flag Pattern Log File Rotation kill -HUP

2 Code Examples  |  5 Interview Questions

5
syslog System — Architecture & Concepts
Why Daemons Need syslog Message Flow Architecture /dev/log Socket Facility Codes Priority Levels Priority Value Encoding

2 Code Examples  |  6 Interview Questions

6
syslog API — openlog, syslog, closelog, setlogmask
openlog() all options LOG_PID / LOG_CONS / LOG_NDELAY %m format specifier vsyslog() setlogmask() LOG_MASK / LOG_UPTO

2 Code Examples  |  6 Interview Questions

7
/etc/syslog.conf — Routing Log Messages
Selector Syntax facility.priority Rules “none” Exclusion Action Types Remote Logging (@host) No-sync (-) prefix

2 Code Examples  |  6 Interview Questions

Start Learning

All 7 parts are ready. Start from the beginning or jump to any topic. Each file is self-contained with theory, code examples, and interview questions.

Start Chapter 37 → Jump to: Creating Daemons

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