What does the killall command do in Linux?

The killall command sends a signal to processes identified by name. It is commonly used to terminate all instances of a running program.

How do I kill a process by its name?

Use 'killall process_name'. For example: 'killall firefox' will terminate all running Firefox processes.

What is the difference between kill and killall?

The kill command terminates processes by their Process ID (PID), while killall terminates processes by their name. killall is often more convenient for stopping all instances of a program.

killall Command

The killall command in Linux is used to terminate running processes by their name. Unlike the kill command which requires a Process ID (PID), killall can send a signal to all processes that match a given name, making it very convenient for stopping all instances of a particular program.

Syntax

killall [OPTION]... PROCESS_NAME...

Description

killall sends a signal to all processes whose executable name matches the provided PROCESS_NAME. By default, it sends the SIGTERM signal, which requests a graceful shutdown. If a process does not respond to SIGTERM, you might need to send a more forceful signal like SIGKILL.

Common uses include:

Terminating all instances of a specific application.
Sending different signals to processes.
Shutting down services gracefully or forcefully.

Common Options

Option	Description
`-e, --exact`	Require exact match for process name.
`-i, --interactive`	Ask for confirmation before killing.
`-o, --older-than <time>`	Kill processes older than specified time (e.g., 1h, 1d).
`-q, --quiet`	Do not complain if no processes were killed.
`-r, --regexp`	Interpret process name as an extended regular expression.
`-s, --signal <signal>`	Send a specific signal instead of SIGTERM.
`-u, --user <user>`	Kill only processes owned by a specific user.
`-v, --verbose`	Report what is being done.

Examples

Kill all instances of a program

killall firefox

Sends a SIGTERM signal to all running processes named firefox.

Forcefully kill a program

                        killall -9 chrome
                        
                        # Or:
                        
                        killall -s SIGKILL chrome

Sends a SIGKILL signal (signal 9) to all chrome processes, which cannot be ignored.

Kill processes owned by a specific user

killall -u john_doe sshd

Kills all sshd processes that are owned by the user john_doe.

Kill processes older than a certain time

killall -o 1h apache2

Kills all apache2 processes that have been running for more than 1 hour.

Interactive killall

killall -i nano

Prompts for confirmation before killing each nano process.