How to Kill a Process in Linux from the Command Line

Why kill a process

1. It does not respond. The process hangs.
2. It uses too many resources. CPU, memory or disk are full.
3. It misbehaves, or it is a security risk.
4. You are debugging and need a clean state.

Find the process ID (PID)

pgrep firefox

Replace firefox with the name of the program. You can also use ps aux | grep name or pidof name.

Method 1: kill

kill [signal] PID

Example:

kill 6407

By default kill sends the TERM signal (15), which asks the process to stop in a clean way. If it does not stop, force it:

kill -9 6407

Method 2: killall

killall ends every process with a given name:

killall [signal] process_name

Example:

killall firefox

Method 3: pkill

pkill matches names with patterns:

pkill [options] pattern

Example, force-kill every match:

pkill -9 firefox

Method 4: top or htop

Start top:

top

Find the process by its PID or by its CPU and memory use. Press k, type the PID, and press Enter to send the signal.

In htop, select the process and press F9.

Common signals

Precautions

• Check the PID before you press Enter.
• Try TERM first. kill -9 gives the process no chance to save data or clean up.
• Do not kill system processes or essential services.
• Use sudo only if the process belongs to another user.

FAQ

What is the difference between kill, pkill and killall? kill uses a PID. killall uses an exact name. pkill uses a pattern and more filters such as user.

A process will not die. Use kill -9 PID. A process in the D state (waiting for disk) may need a reboot.

Quick recap

• Find the PID with pgrep, end it with kill PID.
• Use kill -9 only when the normal signal fails.