2.3. Shutting down, suspending, and hibernating the system

• Shut down the system and power off the machine at a certain time:

  # shutdown --poweroff hh:mm

  Where hh:mm is the time in the 24-hour time notation. To prevent new logins, the /run/nologin file is created 5 minutes before system shutdown.

  When you use the time argument, you can notify users logged in to the system of the planned shutdown by specifying an optional wall message, for example shutdown --poweroff 13:59 "Attention. The system will shut down at 13:59".

• Shut down and halt the system after a delay, without powering off the machine:

  # shutdown --halt +m

  Where +m is the delay time in minutes. You can use the now keyword as an alias for +0.

• Cancel a pending shutdown

  # shutdown -c

  For more information, see the shutdown(8) man page on your system.

Prerequisites

• You have the root access.

Procedure

• Use the systemctl command to perform any of the following tasks:

  • Shut down the system and power off the machine:

    # systemctl poweroff

    You can pass now use --when option in the systemctl command to specify a time.

    注記

    By default, running either of these commands causes systemd to send an informative message to all users that are currently logged into the system. To prevent systemd from sending this message, run the selected command with the --no-wall command line option.

Prerequisites

• You have the root access.

Procedure

• Restart the system:

  # systemctl reboot

  注記

  By default, when you use this command, systemd sends an informative message to all users that are currently logged into the system. To prevent systemd from sending this message, run this command with the --no-wall option.

• Suspend
• Hibernate
• Hybrid Sleep
• Suspend-then-hibernate

Prerequisites

• You have Root access.

• Suspend Suspending 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, the suspended system state is also vulnerable to power outages. To suspend the system, run:

  # systemctl suspend

• Hibernate Hibernating 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. To hibernate the system, run:

  # systemctl hibernate

• Hybrid sleep This combines elements of both hibernation and suspending. The system first saves the current state on the the hard disk drive, and enters a low-power state similar to suspending, which allows the system to resume more quickly. The benefit of hybrid sleep is that if the system loses power during the sleep state, it can still recover the previous state from the saved image on the hard disk, similar to hibernation. To hibernate and suspend the system, run:

  # systemctl hybrid-sleep

• Suspend-then-hibernate This mode first suspends the system, which results in saving the current system state to RAM and putting the system in a low-power mode. The system hibernates if it remains suspended for a specific period of time that you can define in the HibernateDelaySec parameter. Hibernation saves the system state to the hard disk drive and shuts down the system completely. The suspend-then-hibernate mode provides the benefit of conserving battery power while you are still able to quickly resume work. Additionally, this mode ensures that your data is saved in case of a power failure. Suspend and then hibernate the system:

  # systemctl suspend-then-hibernate