Overview
The `halt` command stops all system processes and halts the CPU. Historically, it merely stopped the system, but in many modern systems, it is configured to behave identically to the `poweroff` command. Therefore, it is also used for the purpose of completely shutting down the system.
Key Features
The main features of the `halt` command are as follows:
- Provides the functionality to safely shut down the system
- Stops all processes and halts the CPU
- Behaves identically to 'poweroff' in most modern Linux systems
- Synchronizes file systems before shutdown to prevent data loss
Comparison of Shutdown-Related Commands
halt, reboot, poweroff, and shutdown are all commands related to system shutdown.
- halt: Stops the system and halts CPU functions. Power might remain on, but in modern systems, it also powers off.
- poweroff: Completely shuts down the system and turns off the power. It's a more explicit power-off command than halt.
- reboot: Shuts down the system and immediately restarts it.
- shutdown: Provides scheduled shutdown or reboot functionality at a specific time (e.g., 'now', '+10').
Main Options
Commonly used options for the `halt` command are grouped by purpose.
1) Basic Operation
2) Help
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Description:
`halt` Executes the command.
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Usage Examples
Learn the functionalities of the `halt` command through various usage examples.
Immediately Shut Down the System
sudo haltImmediately shuts down the system. Performs the same action as 'poweroff'.
Force Shutdown
sudo halt -fForces the system to shut down, skipping safety procedures like file system synchronization. Be cautious, as there is a risk of data loss.
Only Record Shutdown
sudo halt -wRecords the shutdown event only in the /var/log/wtmp file, without actually shutting down the system.
Tips & Cautions
Important considerations when using the `halt` command are summarized here.
Tips
- The `halt` command requires root privileges, so it should be used with 'sudo'.
- While `halt` is similar to 'shutdown -h', `shutdown` is safer in server environments as it provides functionality to notify users in advance and schedule shutdowns.
- The difference between `halt` and `poweroff` can vary depending on system configuration. In most modern Linux systems, executing `halt` automatically invokes `poweroff` to turn off the power.