Kill

💥 Command: kill (Terminate a Process)

The kill command is used to send a signal to a running process, usually with the intent to stop it. Despite its aggressive name, it is a communication tool—you are essentially sending a message to a program’s Process ID (PID).

1. The "Why"

Even on a stable system like Arch Linux, applications can freeze or misbehave.

• Stop a Frozen App: If a project build hangs and stops responding.
• Force a Config Reload: Some background services restart or reload their settings when they receive a specific "kill" signal.
• Clean Up: Closing background tasks that you no longer need but that didn't close properly when you exited the GUI.

2. Basic Syntax

kill [SIGNAL] PID

• PID: The Process ID you found using ps or pgrep.
• Signal: The type of "message" you want to send (defaults to 15 if not specified).

3. The Most Common Signals

There are many signals, but you only need to remember these three:

4. Practical Examples

A. The Polite Kill

Suppose you found that your PDF viewer has a PID of 1234. Try this first:

kill 1234

B. The "Nuclear" Option

If the program is completely frozen and ignoring you, use signal 9:

kill -9 1234

C. Killing by Name (pkill)

If you don't want to look up the PID, you can use pkill to target the process name directly:

pkill java

D. Killing Everything with a Specific Name (killall)

If you have five instances of a program running and want them all gone:

killall firefox

5. Pro-Tips

• Permissions: You can only kill processes that you own. If a process is owned by root (like a system service), you must use sudo kill.
• Don't start with -9: Always try a standard kill (signal 15) first. Using -9 (SIGKILL) can sometimes leave "zombie" processes or corrupted files because the app didn't get to finish its cleanup.
• Arch Linux Context: If your Hyprland bar (Waybar) freezes after an update, you can simply run pkill waybar and then start it again from your terminal or runner.

6. Summary Reference