Daemon

A background process that runs continuously on a Linux system, handling services like networking, logging, and scheduling.

A daemon is a type of computer program that runs as a background process on Linux and Unix-like systems, rather than being directly controlled by an interactive user. Daemons typically start during the system boot process and continue running until the system is shut down. They handle essential system services such as web serving (httpd/nginx), secure shell connections (sshd), logging (syslogd), printing (cupsd), and time-based scheduling (crond). By convention, daemon process names often end with the letter 'd'. Modern Linux distributions use systemd as the init system and service manager to start, stop, monitor, and manage daemons. Daemons detach from the controlling terminal and run in the background, often with no direct user interface, and are fundamental to how Linux systems operate as servers and workstations.

System Architecture

Examples

systemctl start nginx - Start the nginx web server daemon

systemctl status sshd - Check the status of the SSH daemon

systemctl enable --now crond - Enable and immediately start the cron daemon

ps aux | grep -E 'd$' - List running processes whose names end with 'd', a common daemon naming convention

Related Terms

kernel cron ssh root sudo