loginctl

What it does

loginctl is a systemd tool that queries and controls the login manager (systemd-logind). It shows who is logged in, what sessions exist, and can terminate sessions/users.

How it works (mechanical)

• Talks to systemd-logind over D-Bus.
• Tracks users, sessions, and seats (seat0 = local console).
• Can terminate a session or user in a controlled way.
• Useful on desktops, multi-user systems, lab servers, and remote access boxes.

10 Practical Examples

# 1) List all active sessions (who is logged in)
loginctl list-sessions

# 2) Show sessions for a specific user
loginctl list-sessions | grep -i craig

# 3) List users known to logind (active/inactive)
loginctl list-users

# 4) Show details for one session (replace 2 with session ID)
loginctl show-session 2

# 5) Show user details (replace UID or username)
loginctl show-user username

# 6) Terminate a single session (kicks that login only)
sudo loginctl terminate-session 2

# 7) Terminate all sessions for a user (kicks user entirely)
sudo loginctl terminate-user username

# 8) Lock/unlock a session (desktop systems; may depend on environment)
loginctl lock-session 2
loginctl unlock-session 2

# 9) List seats (console seats; seat0 is typical)
loginctl list-seats

# 10) Find the session that owns a PID (handy for “who owns this process?”)
loginctl show-session "$(loginctl list-sessions --no-legend | awk 'NR==1{print $1}')" -p Name -p User -p Remote

Notes & Gotchas

• Requires systemd-logind: on non-systemd systems, loginctl won’t exist or won’t work.
• Permission: terminating sessions/users requires root or appropriate polkit permissions.
• SSH sessions: are typically tracked (and can be terminated) but behavior depends on distro/logind config.
• Locking: lock/unlock only applies if a desktop session supports it (GNOME/KDE, etc.).

Historical Context

Before systemd/logind, admins relied heavily on who, w, ps, and manual process killing. loginctl introduced a structured view of sessions and seats with consistent control hooks.

Modern Equivalent

On systemd systems, loginctl is the native “session controller.” For broader identity/session analysis, combine it with: who/w, ps, journalctl, and your directory service tools.

Related Commands

• who, w — logged-in users (classic)
• ps, pkill — process view/control
• systemctl — service manager
• journalctl — logs (who did what and when)
• last — login history