Killall command on Linux (sends signals) [Basic Guide]

The killall command in Linux sends signals to processes and takes as a parameter not the process PID, but its name. It is generally used to terminate the execution of processes that have several processes children performing at the same time.

If no specific signal is passed as a parameter, killall will send the TERM (15) signal to finalize the process in an elegant manner.

In this example, killall forces the web server identified by the httpd name corresponding to processes 1952, 1953, and 1954 to read its configuration file again:

$ ps aux | grep httpd 
wwwrun 1952 0.0 1.7 93232 2248? At 16:15 0:00 /usr/sbin/httpd -f /etc/httpd/httpd.conf 
wwwrun 1953 0.0 1.7 93232 2248? At 16:15 0:00 /usr/sbin/httpd -f /etc/httpd/httpd.conf 
wwwrun 1954 0.0 1.7 93232 2248? At 16:15 0:00 /usr/sbin/httpd -f /etc/httpd/httpd.conf

# killall —HUP httpd

To abruptly terminate the web service by aborting all httpd processes:

# killall —9 httpd

Difference between kill and killall

It’s important that you understand the difference between the kill and killall commands. The former sends signals to one or more processes identified by the PID. The second sends signals to all processes in the execution queue that have a certain name.

The signals sent by Kill and Killall can be passed by name or by the corresponding integer.

The killall command is very similar to the pgrep command.

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