In Linux, an instance of a running service, application, or script is called a process. When you run any command, program, or application, a process is created for it. Each process has its own process id that is associated with a specific user and group. If any processes consume too many resources or become unresponsive, then you may need to kill them. In this case, you can use the kill command to stop the process without restarting your server.
In this post, we will show you how to kill running processes in Linux.
View Running Processes in Linux
The simplest and easiest way to get a list of all running processes is to use the top command. You can run the top command as shown below to list all running processes:
top
You will get all running processes in the following output:
Tasks: 344 total, 1 running, 297 sleeping, 0 stopped, 0 zombie
%Cpu(s): 22.6 us, 6.0 sy, 0.1 ni, 67.1 id, 3.9 wa, 0.0 hi, 0.4 si, 0.0 st
KiB Mem : 7580260 total, 2103076 free, 3174408 used, 2302776 buff/cache
KiB Swap: 2097148 total, 2097148 free, 0 used. 3901388 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5994 vyom 20 0 44344 4160 3444 R 11.8 0.1 0:00.03 top
2206 vyom 20 0 1046476 89792 60368 S 5.9 1.2 1:15.26 Xorg
2359 vyom 20 0 3471324 216412 97596 S 5.9 2.9 1:58.27 gnome-shell
2745 vyom 20 0 1776552 136144 99424 S 5.9 1.8 1:09.93 skypeforlinux
2775 vyom 20 0 37.371g 169524 117660 S 5.9 2.2 1:05.09 skypeforlinux
5655 root 20 0 0 0 0 I 5.9 0.0 0:00.30 kworker/u8:3-ev
1 root 20 0 160356 9464 6632 S 0.0 0.1 0:03.50 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd
3 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_gp
4 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_par_gp
6 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 kworker/0:0H-kb
9 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 mm_percpu_wq
10 root 20 0 0 0 0 S 0.0 0.0 0:00.40 ksoftirqd/0
11 root 20 0 0 0 0 I 0.0 0.0 0:03.58 rcu_sched
12 root rt 0 0 0 0 S 0.0 0.0 0:00.01 migration/0
13 root -51 0 0 0 0 S 0.0 0.0 0:00.00 idle_inject/0
14 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cpuhp/0
15 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cpuhp/1
16 root -51 0 0 0 0 S 0.0 0.0 0:00.00 idle_inject/1
You can press k and enter the process ID to kill the process directly from the top interface.
Also Read
Find Top 10 Running Processes by Memory and CPU Usage
Find the Process Using the ps Command
ps is a command-line utility that will display a complete listing of running processes in the specified format.
The basic syntax of the ps command is shown below:
ps [OPTION]
A brief explanation of each option is shown below:
- -a – Display running processes of all users.
- -u – Display detailed information about each of the processes.
- -x – Display processes that are controlled by the daemon.
For example, run the following command to get a detailed process list of all processes.
ps aux
You will get the following output:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.1 0.1 160356 9464 ? Ss 15:51 0:03 /sbin/init splash root 2 0.0 0.0 0 0 ? S 15:51 0:00 [kthreadd] root 3 0.0 0.0 0 0 ? I< 15:51 0:00 [rcu_gp] root 4 0.0 0.0 0 0 ? I< 15:51 0:00 [rcu_par_gp] root 6 0.0 0.0 0 0 ? I< 15:51 0:00 [kworker/0:0H-kb] root 9 0.0 0.0 0 0 ? I< 15:51 0:00 [mm_percpu_wq] root 10 0.0 0.0 0 0 ? S 15:51 0:00 [ksoftirqd/0] root 11 0.1 0.0 0 0 ? I 15:51 0:03 [rcu_sched] root 12 0.0 0.0 0 0 ? S 15:51 0:00 [migration/0] root 13 0.0 0.0 0 0 ? S 15:51 0:00 [idle_inject/0] root 14 0.0 0.0 0 0 ? S 15:51 0:00 [cpuhp/0] root 15 0.0 0.0 0 0 ? S 15:51 0:00 [cpuhp/1] root 16 0.0 0.0 0 0 ? S 15:51 0:00 [idle_inject/1] root 17 0.0 0.0 0 0 ? S 15:51 0:00 [migration/1] root 18 0.0 0.0 0 0 ? S 15:51 0:00 [ksoftirqd/1] root 20 0.0 0.0 0 0 ? I< 15:51 0:00 [kworker/1:0H-kb] root 21 0.0 0.0 0 0 ? S 15:51 0:00 [kdevtmpfs] root 22 0.0 0.0 0 0 ? I< 15:51 0:00 [netns]
The above command will show you all the running processes. You can use the grep command with the ps command to get a PID of a specific process.
For example, to get a PID of an Apache process, run the following command:
ps aux | grep apache
You will get the following output:
root 1309 0.0 0.0 73992 4748 ? Ss 15:52 0:00 /usr/sbin/apache2 -k start www-data 1310 0.0 0.0 1285068 4620 ? Sl 15:52 0:00 /usr/sbin/apache2 -k start www-data 1311 0.0 0.0 1285068 4644 ? Sl 15:52 0:00 /usr/sbin/apache2 -k start
You can also use the pidof command to get a PID of a specific process.
pidof apache2
You will get the following output:
1311 1310 1309
Kill a Process in Linux
At this point, you know how to get the PID of any process. Now, you can use the kill command to kill a running process.
To kill a single process, run the following command:
kill PID
Or
kill -9 PID
To kill multiple processes, run the following command:
kill -9 PID1 PID2 PID3
You can also kill the processes by their names. You can use the pkill command to kill a process by its name.
To kill the Apache process, run the following command:
pkill apache2
You can also use the killall command to kill a process by its name:
killall mysqld
Also Read
Install Ntopng to Monitor Network Traffic on Ubuntu 20.04
Conclusion
In this post, we explained how to find and kill a process in Linux. You can now kill any unresponsive processes by yourself without restarting your server. Try it on your virtual private server from Atlantic.Net!
