Kill process in Linux or terminate a process in Linux systems

Kill process using kill command under Linux/UNIX

kill command works under both Linux and UNIX/BSD like operating systems.

Step #1: First, you need to find out process PID (process id)

Use ps command or pidof command to find out process ID (PID). Syntax:
ps aux | grep processname
pidof processname
For example if process name is lighttpd, you can use any one of the following command to obtain process ID:
# ps aux | grep lighttpd
# pidof lighttpd
Output:

3486

Step #2: kill process using PID (process id)

Above command tell you PID (3486) of lighttpd process. Now kill process using this PID:
# kill 3486
OR
# kill -9 3486
Where,

• -9 is special Kill signal, which will kill the process.

killall command examples

DO NOT USE killall command on UNIX system (Linux only command). You can also use killall command. The killall command kill processes by name (no need to find PID):
# killall -9 lighttpd
Kill Firefox process:
# killall -9 firefox-bin