What is a Daemon in Linux?

Main Concept

CONCEPT

A daemon is a background process that runs continuously without a user actively interacting with it. It usually provides services to other process or users.

The term comes from the Greek “δαίμων” (daimon), meaning a guiding spirit, not something evil — it’s meant to indicate something that works in the background, invisibly.

Key Aspects

• Runs in the background
• Starts on boot
• Provides services
• Often ends with a ‘d’

Examples

• sshd: Handles SSH connections
• systemd: Manages services an boot processes
• crond: Runs scheduled tasks (cron jobs)
• rsyslogd: Handles system logging
• cupsd: Printer service daemon
• httpd, nginxd: Web servers
• mysqld,postgres: Database servers