Chapter 15. Shutting down, suspending, and hibernating the system

• The support for time argument

  This is particularly useful for scheduled maintenance. Also, users have more time to react to the warning that a system shutdown has been scheduled.

• The option to cancel the shutdown

Prerequisites

• Switch to the root user

Procedure

• To shut down the system and power off the machine at a certain time, use the command in the following format:

  shutdown --poweroff hh:mm

  Where hh:mm is the time in 24 hour clock format. The /run/nologin file is created 5 minutes before system shutdown to prevent new logins.

  When a time argument is used, an optional wall message can be appended to the command.

  Alternatively, to shut down and halt the system after a delay, without powering off the machine, use:

  shutdown --halt +m

  Where +m is the delay time in minutes. The now keyword is an alias for +0.

  To cancel a pending shutdown, use:

  shutdown -c

Prerequisites

• Switch to the root user

Procedure

• To shut down the system and power off the machine, use the command in the following format:

  systemctl poweroff

  Alternatively, to shut down and halt the system without powering off the machine, use:

  systemctl halt

Prerequisites

• Switch to the root user

Procedure

• To restart the system, run the following command:

  systemctl reboot

Prerequisites

• Switch to the root user.

Procedure

• To suspend the system, run the following command:

  systemctl suspend

  This command saves the system state in RAM and with the exception of the RAM module, powers off most of the devices in the machine. When you turn the machine back on, the system then restores its state from RAM without having to boot again.

  Because the system state is saved in RAM and not on the hard disk, restoring the system from suspend mode is significantly faster than from hibernation. However, note that the suspended system state is also vulnerable to power outages.

Prerequisites

• Switch to the root user.

Procedure

• To hibernate the system, run the following command:

  systemctl hibernate

  This command saves the system state on the hard disk drive and powers off the machine. When you turn the machine back on, the system then restores its state from the saved data without having to boot again.

  Because the system state is saved on the hard disk and not in RAM, the machine does not have to maintain electrical power to the RAM module. However, as a consequence, restoring the system from hibernation is significantly slower than restoring it from suspend mode.

  Alternatively, to hibernate and suspend the system, run the following command:

  systemctl hybrid-sleep