Kill process in Linux or terminate a process in UNIX or Linux systems

Q. How do I kill process in Linux?

A. Linux and all other UNIX like oses comes with kill command. The command kill sends the specified signal (such as kill process) to the specified process or process group. If no signal is specified, the TERM signal is sent.

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

Output:

lighttpd 3486 0.0 0.1 4248 1432 ? S Jul31 0:00 /usr/sbin/lighttpd -f /etc/lighttpd/lighttpd.conf
lighttpd 3492 0.0 0.5 13752 3936 ? Ss Jul31 0:00 /usr/bin/php5-cg

OR use pidof command which is use to find the process ID of a running program:

# 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,

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

As I said earlier killall on UNIX system does something else. It kills all process and not just specific process. Do not use killall on UNIX system (use kill -9).

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



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