Killing a process on Linux systems

Have you ever had a stray process eating up all your system resources or just wanted to terminate a program? This HowTo will guide you through the steps of killing any process on your Linux system.


Before getting started, we suggest you Learn Linux Basics and follow these precautions.

Steps to follow

Step 1

While logged in as root, type ps aux | less in your terminal window. This will display a list of all processes currently running, along with their process ID (PID), process status (STAT), command names and various statistics. Read this HowTo for more about viewing running processes on a Linux system.

ps aux | less

Output will be similar to this:

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.1   1992   708 ?        Ss   Jan01   0:00 init [2]  
root         2  0.0  0.0      0     0 ?        S    Jan01   0:00 [migration/0]
root         3  0.0  0.0      0     0 ?        SN   Jan01   0:00 [ksoftirqd/0]
root         4  0.0  0.0      0     0 ?        S    Jan01   0:00 [watchdog/0]
root         5  0.0  0.0      0     0 ?        S<   Jan01   0:00 [events/0]
root         6  0.0  0.0      0     0 ?        S<   Jan01   0:00 [khelper]
root         9  0.0  0.0      0     0 ?        S<   Jan01   0:00 [xenwatch]
root        10  0.0  0.0      0     0 ?        S<   Jan01   0:00 [xenbus]
daemon    1506  0.0  0.0   1924   436 ?        Ss   Jan01   0:00 /usr/sbin/atd
root      1526  0.0  0.1   2044   888 ?        Ss   Jan01   0:00 /usr/sbin/cron
user      9381 16.5 15.0 700080 389304 ?       Sl   Jan01 489:30 /usr/lib/firefox-x.x/firefox
www      28284  0.6  4.5  70036 23972 ?        R    09:51   0:09 /usr/sbin/apache2 -k start
www      28402  0.7  3.9  69620 20944 ?        S    09:59   0:07 /usr/sbin/apache2 -k start
user     28435  0.7  3.9  69600 20732 ?        S    10:06   0:04 /home/user/linuxlookup.pl
Step 2

From the output generated, you need to identify the PID of the process you want to stop. For example, to stop Firefox you would look up the process identification number (PID) in the output and issue the following command:

kill -9 9381

Also, a method of killing all process by name without having to lookup the PID is with:

killall -9 firefox

Note: The processes shown by ps can be narrowed down to a specific program or those belonging to a user by piping the output through grep. For example, processes belonging to a user with a username 'linuxlookup' can be displayed with ps -ef linuxlookup.