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halt command in Linux with examples
  • Last Updated : 21 May, 2019

This command in Linux is used to instruct the hardware to stop all the CPU functions. Basically, it reboots or stops the system. If the system is in runlevel 0 or 6 or using the command with –force option, it results in rebooting of the system otherwise it results in shutdown.

Syntax:

halt [OPTION]...

Options:

Option Description
-f, –force It does not invoke shutdown.
-w, –wtmp-only It will not call shutdown or the reboot system call but writes the shutdown record to /var/log/wtmp file.
-p, –poweroff To behave as poweroff
–verbose Gives verbose messages when reebooting which helps in debugging problems with shutdown.

Files:

  • /var/log/wtmp : Consists a new runlevel record for the shutdown time.
  • /var/run/utmp : Gets updated by a shutdown time record when the current runlevel will be read.

Example 1: To cease all CPU function on the system.



$halt

Output:

Broadcast message from ubuntu@ubuntu
root@ubuntu:/var/log# (/dev/pts/0) at 10:15...
The system is going down for halt NOW.

Example 2: To power off the system using halt command.

$halt -p

Output:

Broadcast message from ubuntu@ubuntu
(/dev/pts/0) at 10:16...
The system is going down for power off NOW.

Example 3: halt command with -w option to write shutdown record.

$halt -w

Note: For this, there will be no output on the screen.

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