halt is a command-line utility in Linux that is used to halt or shut down the system. It is typically used when the system administrator wants to power off the system or bring it to a state where it can be safely powered off.
When the halt command is executed, it sends a request to the kernel to stop all running processes and unmount all file systems. The kernel then performs a clean shutdown of the system, which includes flushing any cached data to disk, closing open files, and shutting down any running services. Once this is complete, the system is powered off or halted.
The halt command can be used with or without any options or arguments. When used without any options or arguments, the command will simply halt the system without any further action. There are different ways to halt a Linux system, such as using shutdown -h now, poweroff or init 0. All these commands does the same thing, which is shutting down the system.
If you encounter the below error while running the command halt:
halt: command not found
you may try installing the below package as per your choice of distribution:
| Distribution | Command |
|---|---|
| Debian | apt-get install sysvinit |
| Ubuntu | apt-get install upstart-sysv |
| Arch Linux | pacman -S systemd-sysvcompat |
| Kali Linux | apt-get install runit-init |
| CentOS | yum install usermode |
| Fedora | dnf install systemd |
| Raspbian | apt-get install upstart |
halt Command Examples
1. Halt the system:
# halt
2. Power off the system (same as `poweroff`):
# halt --poweroff
3. Reboot the system (same as `reboot`):
# halt --reboot
4. Halt immediately without contacting the system manager:
# halt --force --force
5. Write the wtmp shutdown entry without halting the system:
# halt --wtmp-only