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.
