systemdlogind

systemd-logind, sometimes written as systemdlogind, is a core component of the systemd initialization system that provides login, session, and seat management on Linux systems. It tracks user logins and active sessions, manages seats and devices, and coordinates with other system components during session changes and power events.

It operates as a D-Bus service under the org.freedesktop.login1 interface, exposing APIs used by login managers and desktop environments. It does not perform authentication itself; authentication is handled by login programs via PAM or other mechanisms, while logind focuses on session state, device access, and policy checks via PolicyKit.

Historically, systemd-logind replaced ConsoleKit in most distributions and is part of the standard systemd stack. It interacts with the kernel and user space to implement features such as automatic session termination, idle handling, device access control, and session switching between seats.

Usage is commonly through the loginctl tool, which lists and shows sessions and seats and can inspect or terminate sessions. Desktop environments rely on logind to respond to suspend, hibernate, and power key events; policy decisions are governed by PolicyKit.

Configuration is read from /etc/systemd/logind.conf, with various options controlling idle behavior, handling of power and lid switches, and user process management. After changing the configuration, the systemd-logind service typically requires a restart to apply changes. In container or minimal environments, logind may be disabled or not used.

See also: systemd, loginctl, ConsoleKit, PolicyKit, D-Bus, Linux.