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Linux process management improved with htop

Ratchet is to wrench as htop is to top: A more powerful tool to help you get the job done faster.
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htop full output

photo by Tyler Carrigan

Imagine you are working on an engine and need to tighten several bolts within a small space. Now, imagine you had the choice between a ratchet and a wrench. Would you rather make 100 quarter-turns? Or 25 full-turns? This is the level of improvement that htop brings to the table. A well-thought-out, modern interpretation of the top command, htop is my tool of choice for system analytics and process management.

The htop command makes many improvements over the original, the most prominent being in user experience. You can now scroll through the processes, and use point and click functionality. If you want to kill a specific process, scroll down to it and F9 it into oblivion. There is no need to search for the PID or have to use the kill command. Just point and click.

This command runs on Unix, Linux, and macOS. I used the newly released Fedora 31 distro for this demonstration. To install, just run:

$ sudo dnf install htop

You can see the command output in full in this article's title image, but we will break it down section by section as we go along. 

Colors and graphs, oh my!

The first thing to notice is the color inclusion. Color is helpful in identifying specific information and is generally pleasing to the eye. After the chromatic shock, we come to the first graphical representation, which shows us CPU load and memory usage:

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htop cpu graphic

Notice the lines of various colors here in rows marked one through four. These rows represent CPU cores. These colors represent the following in the case of CPUs:

  • Green: CPU utilization owned by normal users (percentage)
  • Blue: CPU utilization by low priority processes
  • Orange: CPU utilization by IRQ time
  • Red: CPU utilization used by system processes

You will also find Mem(ory) and Sw(a)p. The colors for these sections are Green (Ram utilization by pages in memory) and Blue (RAM utilization by buffer pages).

You may see other colors here as well, but for the purpose of this breakdown we will focus on these. You can find more information online if needed.

Just to the right of the bar graph, you will find the following: 

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htop tasks/load average

Let's break this down:

  • 121 tasks (processes), 1 running
  • Load Average: 0.27 0.08 0.02
  • Uptime: 00:52:53

Only tasks that are consuming CPU will show as running, otherwise they can be listed as: 

Symbol Description
S Sleeping
T/S Traced/Stopped
Z Zombies

Note: You can use Shift+k to see the kernel threads and Shift+h to cycle the thread count on/off, as seen here: 

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htop tasks all options

As for the Load average, this is the same as top. Load average is calculated in three intervals: one minute, five minutes, and 15 minutes. These values refer to the amount of time the system has been active since the last reboot.

You can see the same information by running the uptime command.

Individual process breakdown

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HTOP headers

The headers above your process list are as follows, in order of when they appear from left to right:

Symbol Description
PID Process ID number
USER Process owner
PRI Priority level by kernel
N Priority set by user
VIR Virtual memory being used
RES Physical memory being used
SHR Shared memory being used
S Process state
CPU% CPU usage
MEM% Memory usage
TIME+ Time since process started
Command Full command being executed

For more information on htop be sure to check the command's help section by pressing F1: 

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htop help

Try it out

The htop command is, in my opinion, an actual replacement for top. I actually have htop aliased on my systems in place of the standard tool. While I have had a great experience with htop, I recommend that you not take my word for whether it will work for you. Install it and try it out for yourself.

Topics:   Linux  
Author’s photo

Tyler Carrigan

Tyler is a 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. More about me

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