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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