logind

logind logind is a system service component that manages user logins, seats, and session lifecycles on Unix-like operating systems. It coordinates between kernel interfaces, display servers, session managers, and hardware devices to provide multi-user session handling, power management, and device access control. Originating from efforts to modernize init systems and system services, logind is used alongside components of larger system software stacks.

Overview

logind provides session and seat management capabilities for desktop and multi-seat environments, interacting with kernel subsystems and user-space components. It operates within a system service framework to handle terminal logins, graphical sessions, and permission delegation for devices like input devices and graphics cards. The service mediates requests from display servers, login managers, and power management utilities to ensure coherent behavior across components.

Design and Architecture

The architecture of logind is service-oriented and designed to integrate with system-wide init and IPC infrastructures. It uses a central daemon model that exposes APIs over an inter-process communication bus to coordinate with display servers, login managers, and hardware abstraction layers. The design emphasizes modularity so that session lifecycle, seat assignment, and device ACLs can be managed independently while cooperating with compositors, kernel device nodes, and user-space policy agents.

Features and Functionality

logind implements session tracking, seat management, and session activation controls, allowing concurrent graphical and text sessions on multi-seat machines. It manages user session logins, provides APIs for session inhibition and idle handling, and coordinates power operations like suspend and hibernate in response to session activity. The service also handles device access control lists for input devices and DRM nodes, and exposes session and seat information to other system components and user interfaces.

Configuration and Usage

logind is configured through system configuration files and runtime APIs exposed to system administrators, display managers, and desktop environments. Operators adjust settings for idle timeout, automatic suspend, and session policies via configuration files and management tools. Runtime control is typically performed through service management utilities and IPC clients that query session state, activate seats, or request inhibitors for critical operations.

Security and Access Control

logind implements fine-grained access control to devices and session operations to protect user sessions and system integrity. It mediates access to kernel device nodes and grants temporary permissions to processes associated with active sessions, reducing the need for setuid binaries or globally writable device files. The security model interacts with kernel authorization mechanisms and user-space permission frameworks to enforce least privilege for device usage and power control.

Integration and Compatibility

logind integrates with display servers, session managers, and hardware abstraction layers to provide coherent session management across a wide range of environments. It cooperates with graphical stacks and compositors to manage seat assignment, with login programs to authenticate users, and with power management components to coordinate suspend and resume. The component is commonly used in conjunction with modern init systems and desktop environments to enable multi-seat and multi-user workflows.

Development and History

The development of logind traces to efforts to centralize session and seat management within broader system service projects, aiming to replace ad hoc scripts and disparate utilities. Over time it has evolved to address integration with display server protocols, kernel device management changes, and the requirements of contemporary desktop environments and multi-seat deployments. Ongoing maintenance focuses on interoperability, security improvements, and adapting to changes in underlying kernel and user-space APIs.

Category:Operating system components