List all process running linux

Find out what processes are running in the background on Linux

How to find out what processes are running in the background

1. You can use the ps command to list all background process in Linux. Other Linux commands to obtain what processes are running in the background on Linux.
2. top command – Display your Linux server’s resource usage and see the processes that are eating up most system resources such as memory, CPU, disk and more.
3. htop command – Just like a top command but with an improved user interface.

Let us see both traditional command and modern commands examples that one can use to manage running processes in Linux.

How can I run a Linux process in the background?

To run your process or command/shell script in the background, include an & (an ampersand) at the end of the command/shell script you use to run the job. For example:
command &
/path/to/script &
sleep 10000 &

List your background processes

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To stop the foreground process press CTRL + z . One can refers to the background process or stopped process by number. For example, vim is stopped and has 1 as number, so run the bg command to restart a stopped background process:
bg %n
bg %1
One can bring a background process to the foreground such as sleep command using the fg command:
fg %n
fg %2
Finally, kill a running process named “sleep 10000” using the kill command:
kill %n
kill %2

Linux background processes list command

Open the terminal application and issue the following ps command command to show all running process on the system including those running in the background:
$ sudo ps -aux | less
OR
# ps aux | more

List all running processes on Linux using ps command

Understanding ps command outputs

The first column shows the user name who started the foreground or background processes on Linux system. For example, the daemon user started the atd process. The process name itself displayed in the last column. The STAT coloum gives us the state of a Linux process:

Process STATE code	Description
D	uninterruptible sleep (usually IO)
I	Idle kernel thread
R	running or runnable (on run queue)
S	interruptible sleep (waiting for an event to complete)
T	stopped by job control signal
t	stopped by debugger during the tracing
W	paging (not valid since the 2.6.xx kernel)
X	dead (should never be seen)
Z	defunct (“zombie”) process, terminated but not reaped by its parent

Typically process in “interruptible sleep” are running in the background and shows a “ S ” on processes STAT column. The interruptible sleep means the process can be terminated or killed with the help of kill command. On the other hand, processes in a “D” or uninterruptible sleep state are usually waiting on I/O. Therefore, you cannot kill “D” state processes as they are uninterruptible. Additional characters may be displayed as follows too:

Process STATE code	Description
	high-priority (not nice to other users)
N	low-priority (nice to other users)
L	has pages locked into memory (for real-time and custom IO)
s	is a session leader
l	is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)
+	is in the foreground process group

Is my Linux process running in the foreground or background?

Based upon the above tables, one can determine if Linux process in background or foreground or running and so on.

Command/ Process	ps STATE code	Foreground or Background?
/sbin/init	Ss	Background process (interruptible sleep and a session leader)
/usr/sbin/rsyslogd -n	Ssl	Background process (interruptible sleep+a session leader and multi-threaded app)
/sbin/agetty —noclear	Ss+	Background process (interruptible sleep and a session leader and is in foreground group)
ps aux	R+	Running foreground process

Use the following command to list Linux processes along with pid, user name, stat as follows:
ps -eo pid,user,stat,comm
You can combine ps with grep command command as follows:
ps -eo pid,user,stat,comm | grep nginx

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How to check running process in Linux using command line

I am a new system administrator for the Linux operating system. How do I check running process in Linux using the command line option?

Tutorial details
Difficulty level	Easy
Root privileges	Yes
Requirements	Linux terminal
Est. reading time	4 mintues

One can use the Linux command line or terminal app to display a running process, change their priorities level, delete process and more. This page shows how to use various commands to list, kill and manage process on Linux.

Check running process in Linux

The procedure to monitor the running process in Linux using the command line is as follows:

1. Open the terminal window on Linux
2. For remote Linux server use the ssh command for log in purpose
3. Type the ps aux command to see all running process in Linux
4. Alternatively, you can issue the top command or htop command to view running process in Linux

Let us see some example and usage in details.

Please note that vivek@nixcraft:

$ is my shell prompt. You need to type commands after the $ prompt.

How to manage processes from the Linux terminal

The ps command is a traditional Linux command to lists running processes. The following command shows all processes running on your Linux based server or system:
vivek@nixcraft:

$ ps -aux
vivek@nixcraft:

1. root – User name
2. 1 – PID (Linux process ID)
3. 19:10 – Process start time
4. /sbin/init splash – Actual process or command

There may be too many processes. Hence, it uses the following less command/more command as pipe to display process one screen at a time:
vivek@nixcraft:

$ ps -aux | more
vivek@nixcraft:

$ sudo ps -aux | less
Press q to exit from above Linux pagers. You can search for a particular Linux process using grep command/egrep command:
vivek@nixcraft:

$ ps aux | grep firefox
vivek@nixcraft:

$ sudo ps aux | grep vim
vivek@nixcraft:

$ sudo ps -aux | egrep ‘sshd|openvpn|nginx’

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• Join my Patreon to support independent content creators and start reading latest guides:
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  • How To Set Up SSH Keys With YubiKey as two-factor authentication (U2F/FIDO2)
  • How to set up Mariadb Galera cluster on Ubuntu or Debian Linux
  • A podman tutorial for beginners – part I (run Linux containers without Docker and in daemonless mode)
  • How to protect Linux against rogue USB devices using USBGuard

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Linux pgrep command

Many variants of Linux comes with the pgrep command to search/find process. The syntax is:
vivek@nixcraft:

$ sudo pgrep sshd
vivek@nixcraft:

$ pgrep vim
vivek@nixcraft:

$ pgrep firefox
vivek@nixcraft:

Linux top command

The top command is another highly recommended method to see your Linux servers resource usage. One can see a list of top process that using the most memory or CPU or disk.
vivek@nixcraft:

$ sudo top
vivek@nixcraft:

Linux htop command to check running process in Linux

The htop command is an interactive process viewer and recommended method for Linux users. One can see a list of top process that using the most memory or CPU or disk and more:
vivek@nixcraft:

$ sudo htop
vivek@nixcraft:

Linux kill command

Want to kill a process? Try kill command. The syntax is:
vivek@nixcraft:

$ kill pid
vivek@nixcraft:

$ kill -signal pid
Find PID using ps, pgrep or top commands. Say you want to kill a PID # 16750, run:
vivek@nixcraft:

$ kill 16750
For some reason if the process can not be killed, try forceful killing:
vivek@nixcraft:

$ kill -9 16750
OR
vivek@nixcraft:

$ kill -KILL 16750

Linux pkill command

If you wish to kill a process by name, try pkill command. The syntax is:
vivek@nixcraft:

$ pkill processName
vivek@nixcraft:

$ pkill vim
vivek@nixcraft:

$ pkill firefox
vivek@nixcraft:

$ pkill -9 emacs
vivek@nixcraft:

$ sudo pkill -KILL php7-fpm

Linux killall command

The killall command kills processes by name, as opposed to the selection by PID as done by kill command:
vivek@nixcraft:

$ killall vim
vivek@nixcraft:

$ killall -9 emacs

Linux nice and renice command

The primary purpose of the nice command is to run a process/command at a lower or higher priority. Use the renice command to alter the nice value of one or more running Linux processes. The nice value can range from -20 to 19, with 19 being the lowest priority. Say, you want to compile software on a busy Linux server. You can set a very low priority, enter:
vivek@nixcraft:

$ nice -n 13 cc -c *.c &
Set a very high priority for a kernel update. Before rebooting Linux server, run:

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How to List Running Processes in Linux: A Beginner’s Guide

Need to view all running processes on your Linux server and discover which consumes your resources the most? Look no further, because, in this article, we’ll explain how to list Linux processes by using several common commands.

Introduction to Linux Processes

A process is the execution of a program. They can be launched when opening an application or when issuing a command through the command-line terminal.

A command can only generate a process. However, an application can run multiple processes for different tasks. For instance, Google Chrome will start a different process each time a new tab is opened.

Each Linux process is assigned a unique PID (process identification number). If there are no possible combinations left, the system can reuse old PIDs for newer processes.

A process can be initiated as a foreground or background process.

By default, all commands that run in the shell will start as foreground processes. As the process occupies the shell, you have to wait until it is finished before executing other commands.

If a command takes too long to complete, you can run it as a background process by adding an ampersand (&) at the end of the command so you can use the shell for other tasks.

Occasionally, processes may consume a lot of resources and need to be killed. Alternatively, times when you may want to change the priority level of a process, so the system will allocate more resources to it. Regardless of the case, all these tasks require you to do the same thing: listing the running processes on Linux.

How to List Running Processes in Linux?

There are several commands that you can use to list running processes: ps, top, and htop.

Utilizing the “ps” Command

The ps (process statuses) command produces a snapshot of all running processes. Therefore, unlike the Windows task manager, the results are static.

When this command is used without any additional argument or option, it will return a list of running processes along with four crucial columns: the PID, terminal name (TTY), running time (TIME), and the name of the command that launches the process (CMD). You can use ps aux to get more in-depth information about your running processes. Here’s a breakdown of each argument:

• a option outputs all running processes of all users in the system.
• u option provides additional information like memory and CPU usage percentage, the process state code, and the owner of the processes.
• x option lists all processes not executed from the terminal. A perfect example of this are daemons, which are system-related processes that run in the background when the system is booted up.

If you want to list Linux processes in a hierarchical view, use the ps -axjf command. In this format, the shell will put child processes under their parent processes. Aside from those two options, here are some other common examples of the ps command that list running processes in Linux:

• ps -u [username] lists all running processes of a certain user.
• ps -e or ps -A displays active Linux processes in the generic UNIX format.
• ps -T prints active processes that are executed from the terminal.
• Ps -C process_name will filter the list by the process name. In addition, this command also shows all child processes of the specified process.

Using the “top” Command

The top command is used to discover resource-hungry processes. This Linux command will sort the list by CPU usage, so the process which consumes the most resources will be placed at the top.

Unlike the ps command, the output of the top command is updated periodically. That means you’ll see real-time updates for CPU usage and running time. Once the shell returns the list, you can press the following keys to interact with it:

Keys	Functions
k	Kills a process
M	Sorts the list by memory usage.
N	Sorts the list by PID.
r	Changes the priority of a process.
h	Displays the help window.
z	Displays running processes in colors.
d	Changes the refresh time interval.
c	Displays the absolute path of a process.
CTRL+C or q	Stops the top command.

Keep in mind that the keys above are case sensitive, so be sure not to enable the caps lock.

Running “htop” Command

Both the htop and top command display the same information when listing your Linux processes, but the former offers user-friendly features that are great for everyday process management.

First thing first, the htop command allows you to scroll vertically and horizontally. As such, you can see the complete list of your Linux processes along with their full command lines.

What’s more, the command allows you to use a mouse to select items, kill processes without inserting their PIDs, change the priority of multiple processes easily, and so on.

Unfortunately, most Linux distributions don’t have this command right out of the box, so you need to install it manually.

If you use Ubuntu, you can install htop by running the following command:

Once installed, type htop, and you’ll get a list of all your Linux processes. Just like the previous command, htop also has several keyboard shortcuts:

Keys	Functions
F9	To kill a process.
F8	Increase the priority of a process.
F7	Decrease the priority of a process.
F6	Sort processes by any column.
F5	Display processes in a tree view.
F4	Filter the processes by name.
F3	Search for a process.
F2	Open htop setup.
F1	Display the help menu.

Conclusion

It is important to know how to list all running processes in your Linux operating system. The knowledge will be useful when you need to manage processes.

Let’s take a look once more at the three commands that you can use to list Linux processes:

• ps command — outputs a static view of all processes.
• top command — displays the real-time list of all running processes.
• htop command — shows the real-time result and is equipped with user-friendly features.

Which command do you prefer? Share your thoughts in the comment section below!

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