Halt Command in Linux
Linux is a quite powerful operating system, and, as such, Linux machines rarely need to be rebooted. However, sometimes there are some instances where you do need to reboot your system. For instance, if you're running Linux on your personal computer, rebooting and shutting down the system could be useful for everyday operations. This is where the halt command comes into play. This command halts the system by shutting it down in an orderly manner. You can use this command to turn off the system or reboot it.
The halt command also instructs the hardware to stop all CPU functions, leaving it powered on. Besides this, you can use this command to get the system to a state where you can perform low-level maintenance.
Table of Contents
Here is a comprehensive guide to the options available with the Halt command −
Syntax for the halt Command
The following is the general syntax for the halt command −
halt [OPTION]...
Options halt Command
The following are different options for the halt command with their descriptions −
| Tag | Description |
|---|---|
| -f, --force | Does not invoke the shutdown command and instead performs the actual action you would expect from the name. |
| -p, --poweroff | Instructs the halt command to behave as poweroff. |
| -w, --wtmp-only | Does not call shutdown or the reboot system call and instead only writes the shutdown record to /var/log/wtmp. |
| --verbose | Outputs slightly more verbose messages when rebooting, useful for debugging problems with shutdown. |
Examples of halt Command in Linux
In this section, weâll explore various examples of the halt command using the options weâve discussed above −
- Halt the System
- Power Off the System
- Reboot the System
- Force Halt
- Write Shutdown Record Only
Halt the System
The first use case of this command is to simply halt the system. You can achieve this by executing the following command −
halt
This command stops all the processes and shuts down the system properly without rebooting or taking any other action.
Power Off the System
To power off your system using the halt command, you can add the --poweroff option or -p flag as shown below −
halt --poweroff
OR
halt -p
This command shuts down the system and turns off the power completely.
Reboot the System
To reboot the system using the halt command, you can simply use the --reboot option as shown −
halt --reboot
This command shuts down the system and restarts it instantly.
Force Halt
To halt the system forcefully without invoking the shutdown command, you can use the -f flag or --force argument −
halt -f
OR
halt --force
This command forcefully halts the system immediately, ignoring any background processes that the system manager might be handling.
Write Shutdown Record Only
To write the shutdown record to /var/log/wtmp without actually halting the system, you can use the -w flag or --wtmp-only argument −
halt --wtmp-only
OR
halt -w
This command updates the wtmp file with the shutdown entry, but your system will continue to run as usual.
Conclusion
In this tutorial, we explored the use-case of the halt command. Whether you want only to update the wtmp file, halt your system, power it off, reboot it, or force a halt, the halt command provides all options to suit your needs.