Managing Processes
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In this lesson, you will learn how to manage processes on a Linux server. You will learn tools like ps, top, and kill. We will use the nginx package as our example. To get started, go ahead and install the nginx package with the command below:
sudo apt install nginxUnderstanding NGINX as a Process
When NGINX is running on your Ubuntu Server, it operates as a process. This process can be viewed, managed, and terminated if necessary, using Linux commands. Knowing how to view and kill processes is an extremely important skill that I want to make sure you understand - so we will cover that in this lesson.
The top utility
The top command in Linux is an incredibly useful tool for monitoring system performance and managing processes. It provides a real-time, dynamic view of your system's resource usage, including CPU, memory, and process information. In this lesson, we'll focus on some essential skills you should have when using top, with a special emphasis on searching for process names.
Opening top
To start top, simply type the following command in your terminal:
topNavigating the top Interface
Once top is running, you'll see a display showing a list of the system's currently running processes, along with information about system resources. The top portion shows overall system statistics, while the bottom portion lists individual processes.
Sorting Processes
By default, top sorts processes based on CPU usage, but you can sort by other criteria (you must use shift to capitalize each of the letters below):
Searching for Process Names
One key skill in top is searching for specific processes by name. This is particularly useful when you're monitoring a specific application or service. To search for a process:
If there are multiple instances of the process, you can press L and enter the name again to cycle through them.
Killing Processes from top
If you find a process that needs to be terminated, you can do so directly from top:
Forcefully kill all the nginx processes, then exit top using the instructions below.
Exiting top
To exit top, simply press q. This will return you to the command line. Check the status of nginx to make sure it was stopped:
paulh@ubuntu-server:~$ systemctl status nginx
× nginx.service - A high performance web server and a reverse proxy server
Loaded: loaded (/lib/systemd/system/nginx.service; disabled; vendor preset: enabled)
Active: failed (Result: signal) since Tue 2023-12-05 20:37:57 UTC; 9s ago
Docs: man:nginx(8)
Process: 74006 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=0>
Process: 74007 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
Main PID: 74008 (code=killed, signal=KILL)
CPU: 20msThen you can start nginx back up with the command below:
sudo systemctl status nginxViewing Processes with ps
Use the ps command with options aux piped to the grep command to filter for all NGINX processes:
ps aux | grep nginxThis should return an output similar to the following:
I manually added the first line in the output below so you can see each column name, but you will be missing the first row due to the grep command filtering it out
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 74008 0.0 0.0 55220 1680 ? Ss 20:30 0:00 nginx: master process /usr/sbin/nginx -g daemon on; master_process on;
www-data 74009 0.0 0.0 55852 5608 ? S 20:30 0:00 nginx: worker process
www-data 74010 0.0 0.0 55852 5608 ? S 20:30 0:00 nginx: worker process
www-data 74011 0.0 0.0 55852 5608 ? S 20:30 0:00 nginx: worker process
www-data 74012 0.0 0.0 55852 5608 ? S 20:30 0:00 nginx: worker process
paulh 74027 0.0 0.0 6476 2220 pts/0 S+ 20:30 0:00 grep --color=auto nginxKilling processes with kill
If you need to stop the NGINX process, perhaps due to unresponsiveness or for maintenance purposes, you can do so using the kill command.
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