logind
also: systemd-logind, user-logind
A systemd service that manages user login sessions, device access, and power state transitions on Linux systems.
logind is a core systemd component that tracks and manages user sessions across login/logout events. It handles seat allocation (mapping of users to physical input/output devices), device access permissions, and ensures proper cleanup when users disconnect.
When you log in via SSH, the graphical login manager, or a terminal, logind creates a session object tracking that login. It manages which user owns which devices (keyboard, mouse, display) and coordinates with other system services to enforce device access rules.
Example: When you unplug a USB drive while logged in, logind tracks device ownership and can enforce unmount rules. When you log out, logind signals all associated processes and cleans up session resources, ensuring no orphaned processes or lingering device locks remain.