Suppose you find yourself exploring the Linux command line for the first time or entering into Linux administration. In that case, a low-level understanding of how to get around the terminal and complete basic tasks is essential. To help you grasps those concepts, check out my previous two articles:
However, if you feel comfortable with those concepts, we will advance your Linux knowledge a bit further in this article. We will be looking at processes and how to manage them.
So, what exactly is a process?
In Linux, a process is any active (running) instance of a program. But what is a program? Well, technically, a program is any executable file held in storage on your machine. Anytime you run a program, you have created a process. At a basic level, this is pretty easy to manage, and that is what we are going to take a look at today.
What you need to get started
I recommend that you follow along on your favorite virtual machine. That way, you can try and fail without consequence (which is definitely the best way to get comfortable at the terminal).
For this demo, I am going to start the sleep process for 500 seconds. This approach allows you to see the process without me making meaningful changes to my system.
[tcarrigan@client ~]$ sleep 500
^Z
[1]+ Stopped sleep 500
I then stopped the process with Ctrl+Z so that we can use our terminal.
1. List processes
To display your currently active processes, use the ps
command:
[tcarrigan@client ~]$ ps
PID TTY TIME CMD
2648 pts/0 00:00:00 bash
3293 pts/0 00:00:00 sleep
3300 pts/0 00:00:00 ps
Here you get a little information about the active processes on your system. You will want to pay attention to the PID (unique process ID), the TIME (amount of time that the process has been running), and the CMD (the command executed to launch the process).
2. Verbose list (processes)
To see an incredibly detailed list of processes, you can use the ps aux
command.
- a - all users
- u - shows the user/owner
- x - displays processes not executed in the terminal (making the output rather long)
You can see the command here (output edited for length):
[tcarrigan@client ~]$ ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
tcarrig+ 3293 0.0 0.0 215292 520 pts/0 T 13:41 0:00 sleep 500
root 3380 0.0 0.0 0 0 ? I 13:45 0:00 [kworker/1:1-mm_percpu_wq]
root 3381 0.0 0.0 0 0 ? I 13:45 0:00 [kworker/1:3]
root 3398 0.0 0.0 0 0 ? I 13:46 0:00 [kworker/3:2-ata_sff]
root 3481 0.0 0.0 0 0 ? I 13:50 0:00 [kworker/u8:2-flush-253:0]
root 3482 0.0 0.0 0 0 ? I 13:50 0:00 [kworker/0:1-events]
root 3483 0.0 0.0 0 0 ? I 13:50 0:00 [kworker/0:2]
root 3508 0.0 0.0 0 0 ? I 13:51 0:00 [kworker/3:0-ata_sff]
root 3511 0.0 0.0 18892 7732 ? S 13:52 0:00 systemd-userwork
root 3512 0.0 0.0 18892 7656 ? S 13:52 0:00 systemd-userwork
root 3513 0.0 0.0 18892 7656 ? S 13:52 0:00 systemd-userwork
root 3566 0.4 0.0 432792 8024 ? Ssl 13:54 0:00 /usr/libexec/fprintd
tcarrig+ 3598 0.0 0.0 228208 3948 pts/0 R+ 13:54 0:00 ps aux
3. Kill by PID
Inevitably, a process will get hung, and you will need to kill
it. The more time you spend at the CLI, the more likely it is you will need the kill
command. The most accurate way to identify a process is by process ID (PID).
Use the following syntax:
[tcarrigan@client ~]$ kill PID
This command sends the SIGTERM signal. However, if you are dealing with a stuck process, add the -9
option.
[tcarrigan@client ~]$ ps
PID TTY TIME CMD
2648 pts/0 00:00:00 bash
3293 pts/0 00:00:00 sleep
4684 pts/0 00:00:00 sleep
40527 pts/0 00:00:00 sleep
40540 pts/0 00:00:00 ps
[tcarrigan@client ~]$ sudo kill -9 3293
[sudo] password for tcarrigan:
[1] Killed sleep 500
4. Kill by name/keyword
Use the killall
command to kill a process by name. This command will kill all processes with the keyword/name that you specify.
The syntax is:
[tcarrigan@client ~]$ killall sleep
This would kill all sleep
processes active on the system (the -9
option works here as well). Here is an example:
[tcarrigan@client ~]$ ps
PID TTY TIME CMD
2648 pts/0 00:00:00 bash
4684 pts/0 00:00:00 sleep
40527 pts/0 00:00:00 sleep
40540 pts/0 00:00:00 ps
[tcarrigan@client ~]$ killall -9 sleep
[2]- Killed sleep 500
[3]+ Killed sleep 500
These next two commands go hand in hand. They allow you to move/manage background commands. I will give a basic look at the syntax below; however, for an in-depth look at these commands, see my previous article on the subject.
5. List background jobs and resume background jobs
To list and manage background jobs, we will use the bg
command. I started a new sleep 500
process and then stopped it, sending it to the background. Thus we see it listed when running bg
below:
[tcarrigan@client ~]$ bg
[1]+ sleep 500 &
6. Bring the most recent job to the foreground
To do this, we are going to use the fg
command. This brings the most recently run job/process to the foreground. The following example is a continuation of the above command. The sleep 500
process that is in the background is now active in the background. Let's bring it into the light...
[tcarrigan@client ~]$ fg
sleep 500
This command brings us to our final command in this list.
7. Bring a specific job to the foreground
Use the fg
command again, but select a specific job to bring to the foreground (instead of the most recent). To do this, we are just going to add the job/process name to the command.
[tcarrigan@client ~]$ fg XXXample
This brings job XXXample to the foreground.
[ Want to test your sysadmin skills? Take a skills assessment today. ]
Wrapping up
In today's Linux Command Basics, we looked at processes and how to manage them. You can now complete general process management tasks—everything from listing and killing to moving between the background and foreground. If there are other general Linux administration areas that you would like to see a dedicated list of commands for, email the team at enable-sysadmin@redhat.com, and I will do my best to flesh that out for you.
About the author
Tyler is the Sr. Community Manager at Enable Sysadmin, a submarine veteran, and an all-round tech enthusiast! He was first introduced to Red Hat in 2012 by way of a Red Hat Enterprise Linux-based combat system inside the USS Georgia Missile Control Center. Now that he has surfaced, he lives with his wife and son near Raleigh, where he worked as a data storage engineer before finding his way to the Red Hat team. He has written numerous technical documents, from military procedures to knowledgebase articles and even some training curricula. In his free time, he blends a passion for hiking, climbing, and bushcraft with video games and computer building. He is loves to read and enjoy a scotch or bourbon. Find him on Twitter or on LinkedIn.
Browse by channel
Automation
The latest on IT automation for tech, teams, and environments
Artificial intelligence
Updates on the platforms that free customers to run AI workloads anywhere
Open hybrid cloud
Explore how we build a more flexible future with hybrid cloud
Security
The latest on how we reduce risks across environments and technologies
Edge computing
Updates on the platforms that simplify operations at the edge
Infrastructure
The latest on the world’s leading enterprise Linux platform
Applications
Inside our solutions to the toughest application challenges
Original shows
Entertaining stories from the makers and leaders in enterprise tech
Products
- Red Hat Enterprise Linux
- Red Hat OpenShift
- Red Hat Ansible Automation Platform
- Cloud services
- See all products
Tools
- Training and certification
- My account
- Customer support
- Developer resources
- Find a partner
- Red Hat Ecosystem Catalog
- Red Hat value calculator
- Documentation
Try, buy, & sell
Communicate
About Red Hat
We’re the world’s leading provider of enterprise open source solutions—including Linux, cloud, container, and Kubernetes. We deliver hardened solutions that make it easier for enterprises to work across platforms and environments, from the core datacenter to the network edge.
Select a language
Red Hat legal and privacy links
- About Red Hat
- Jobs
- Events
- Locations
- Contact Red Hat
- Red Hat Blog
- Diversity, equity, and inclusion
- Cool Stuff Store
- Red Hat Summit