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halt

system managementLinux/Unix

The halt command is one of the most frequently used commands in Linux/Unix-like operating systems. halt Stop the system

See Examples View Syntax

Quick Reference

Command Name:

halt

Category:

system management

Platform:

Linux/Unix

Basic Usage:

halt [options] [arguments]

Common Use Cases

Syntax

halt [options]

Options

Option	Description
`-d, --no-wtmp`	Don't write a wtmp record
`-f, --force`	Force halt, don't call shutdown
`-h, --help`	Display help message and exit
`-n, --no-sync`	Don't sync before halting
`-p, --poweroff`	Turn the machine off (as with poweroff)
`-w, --wtmp-only`	Just write the wtmp record, don't actually halt the system
`--no-wall`	Don't send wall message before halting

Examples

How to Use These Examples

The examples below show common ways to use the halt command. Try them in your terminal to see the results. You can copy any example by clicking on the code block.

# Basic Examples Basic

sudo halt

Halt the system (stop all processes and shut down the CPU).

sudo halt -p

Power off the machine (equivalent to 'poweroff').

# Advanced Examples Advanced

sudo halt -f Force halt, don't call shutdown command. sudo halt -w Don't actually halt the system, just write the wtmp record. sudo halt --no-wall Don't send wall message before halting.

Try It Yourself

Practice makes perfect! The best way to learn is by trying these examples on your own system with real files.

Understanding Syntax

Pay attention to the syntax coloring: commands, options, and file paths are highlighted differently.

Notes

The halt command is used to stop all CPU functions on the system. It brings the system down in a secure way, first terminating all processes, then writing data to disk, and finally instructing the hardware to stop operating. Key features of halt: 1. System Shutdown: halt stops all processes and essentially shuts down the system, but unlike poweroff, it may not actually turn off the power to the machine depending on the hardware and system configuration. 2. Administrative Privileges: In most systems, halt requires root privileges or administrative access to execute, as it affects the entire system. 3. Process Termination: Before halting, the system sends termination signals to all running processes, allowing them to close gracefully and save their state if needed. 4. Data Synchronization: By default, halt ensures that all data in memory is written to disk (synchronized) before stopping the system, which helps prevent data loss. 5. Event Logging: The system logs the halt event in the wtmp file, which keeps track of system bootups and shutdowns, unless specifically instructed not to with the -d option. 6. Power Management Options: With the -p option, halt acts like the poweroff command, fully powering down the machine if the hardware supports it. 7. Forced Shutdown: The -f option allows forcing a halt without going through the normal shutdown sequence, which is generally not recommended as it can lead to data loss. In modern Linux systems, halt is often a symbolic link to the systemctl command, which is part of the systemd init system. The recommended way to halt a systemd-based system is with 'systemctl halt'. It's worth noting that on many modern systems, the differences between halt, poweroff, and shutdown commands have become somewhat blurred, as they often use the same underlying mechanisms. The specific behavior might vary slightly depending on the distribution and system configuration.

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These commands are frequently used alongside halt or serve similar purposes:

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Use Cases

Learn By Doing

The best way to learn Linux commands is by practicing. Try out these examples in your terminal to build muscle memory and understand how the halt command works in different scenarios.

See Examples Try Lab Exercises

$ halt

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