shutdown / reboot / poweroff / halt

Overview

These commands schedule or request system power state changes. On systemd systems they talk to logind/PID 1. Prefer clear wall messages on multi-user hosts.

Syntax

sudo shutdown [options] when [message]
sudo reboot
sudo poweroff
sudo halt

when forms

now, +minutes, hh:mm.

Common Options (shutdown)

Option	Description
-h	Halt/power off
-r	Reboot
-c	Cancel scheduled
-k	Wall only, no shutdown

Examples with Explanations

sudo shutdown -h now
sudo shutdown -r +15 "kernel update reboot"
sudo shutdown -r 23:30 "nightly reboot"
sudo shutdown -c
sudo reboot
sudo systemctl reboot
sudo systemctl poweroff

systemd equivalents

sudo systemctl reboot
sudo systemctl poweroff
sudo systemctl suspend

Safety

• Unsaved work will be lost; notify users (wall).
  
• Remote: ensure out-of-band console if reboot fails.
  
• Cloud providers may have separate stop/restart APIs.

Related Commands

• systemctl
  
• loginctl
  
• wall
  
• last reboot