This encyclopedia entry provides a detailed introduction to daemons, the basic background services of Linux and Unix-like systems. The article starts with the mythological origin of the word "daemon" and explains the technical significance of the concept, showing how programs become independent, autonomous processes independent of the user. It deals in detail with the management of daemons in modern Linux distributions using the systemd init system and the systemctl command, illustrating the querying of the status of services, starting and stopping them through practical examples and screenshots. The description also provides insight into the deeper layers of systemd configuration with a detailed analysis of a real sshd.service unit file. The article finally concludes with an introduction to the most common daemons (e.g. sshd, apache2, cron), giving a comprehensive overview of these essential components for system operation.