Daemons

A daemon is a program that runs as a "background" process (without a terminal or user interface), commonly waiting for events to occur and offering services. A good example is a web server that waits for a request to deliver a page, or a ssh server waiting for someone trying to log in. While these are full featured applications, there are daemons whose work is not that visible. Daemons are for tasks like writing messages into a log file (e.g. syslog, metalog) or keeping your system time accurate (e.g. ntpd). For more information see daemon(7).

In Arch Linux, daemons are managed by systemd. The systemctl command is the user interface used to manage them. It reads name.service files that contain information about how and when to start the associated daemon. For directories containing system-wide service files see systemd#Writing unit files; for the respective user specific files, see systemd/User#How it works.

See also systemd#Using units for further details.