halt, poweroff and reboot Commands in Linux

Below are typical uses of halt, poweroff and reboot.

  1. halt : Instructs hardware to stop CPU functions.
  2. poweroff : Instructs the system to power down.
  3. reboot : Restarts or reboots the system.

The above mentioned commands can only be run by super user as these involve the actions to stop the system hardware. If the user is not logged in as super user then sudo command can be used to run these commands.

halt Command

This instructs the hardware to stop all the CPU functions.



// syntax of halt command
halt [OPTION]...

The halt simply can be used to halt, poweroff and reboot the system :

  • //  Instructs hardware to stop CPU functions.
    halt
    
  • // power off the system
    halt -p
    
  • // reboots the system 
    halt --reboot
    

Applications

  • This lets the user to power down the system from the command line.
  • Using halt all the CPU functions will be stopped and system will enter a state where user can perform low level maintenance.

poweroff Command

poweroff Sends an ACPI signal which instructs the system to power down. Here’s the syntax of poweroff command :

// syntax of poweroff
poweroff [OPTION]...

The poweroff simply can be used to halt, poweroff and reboot the system as :

  • // Powers off the system
    poweroff
  • // Halts the system
    poweroff --halt
    
  • // Reboots the system 
    poweroff --reboot
    

reboot Command

the reboot command instructs the system to restart or reboot. Here’s the syntax of reboot command :

// syntax of reboot
reboot [OPTION]...

The reboot simply can be used to halt, poweroff and reboot the system as :

  • // Halts the system
    reboot --halt
    
  • // Powers off the system
    reboot -p
    
  • // Reboots the system 
    reboot
    


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