Shutdown Command

shutdown schedules a time for the system to be powered down. It may be used to halt, power-off or reboot the machine.

You may specify a time string (which is usually “now” or “hh:mm” for hour/minutes) as the first argument. Additionally, you may set a wall message to be sent to all logged-in users before the system goes down.

Important: If the time argument is used, 5 minutes before the system goes down the /run/nologin file is created to ensure that further logins will not be allowed.

Examples of shutdown commands:

# shutdown
# shutdown now
# shutdown 13:20  
# shutdown -p now	#poweroff the machine
# shutdown -H now	#halt the machine		
# shutdown -r09:35	#reboot the machine at 09:35am

To cancel a pending shutdown, simply type the command below:

# shutdown -c


Halt Command

halt instructs the hardware to stop all CPU functions but leaves it powered on. You can use it to get the system to a state where you can perform low-level maintenance. In some cases, it completely shuts down the system. 


Below are examples of halt commands:

# halt		   #halt the machine
# halt -p	   #poweroff the machine
# halt --reboot    #reboot the machine


Power off Command

poweroff sends an ACPI signal which instructs the system to power down.

Examples of poweroff commands:

# poweroff   	       #poweroff the machine
# poweroff --halt      #halt the machine
# poweroff --reboot    #reboot the machine


Reboot Command

reboot instructs the system to restart.

# reboot            #reboot the machine
# reboot --halt     #halt the machine
# reboot -p   	    #poweroff the machine


That’s all! 

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