htop command in linux For any Linux administrator the ability to monitor their systems performance is a critical task to ensure optimal functionality.
Using the right type of monitoring tool can be the difference between hours of lost productivity due to system downtime and being able to resolve issues quickly and with minimal effort.
For many years, Linux users relied solely on the top command which displays the processes that consume CPU and memory resources.
Although the top command serves it purpose well, the speed at which our systems operate and the volume of resources our systems consume necessitated a more visual and interactive display that would make it much easier for the average user to interpret. Thus, the introduction of htop for Linux.
htop in linux is designed to be a user-friendly, interactive terminal-based monitor for viewing your system’s real-time activity in a way that is easy to interpret, organized, colour-coded and informative at a glance.
The novice user will be able to easily determine the level of CPU usage, as well as how much memory and swap space the machine has available and what processes consume the most resources.
This complete novice-friendly beginner’s article for htop command in Linux will walk you through the steps to install and use htop, as well as show you how to customize and configure htop to fit your specific needs while providing you with the confidence to monitor and manage your Linux system from the terminal.
Table of Contents
- 1. What is htop in linux?
- 2. How to Install htop in linux (All Distributions)
- 3. Understanding the Dashboard Architecture
- 4. Decoding CPU and Memory Meters
- 5. The Process Table: Every Column Explained
- 6. Mastering Interactive Keyboard Shortcuts
- 7. Advanced Sorting and Filtering Techniques
- 8. Managing Tasks: Killing and Renicing Processes
- 9. Customizing the htop Interface (F2 Menu)
- 10. Real-World Troubleshooting with htop in linux
- 11. Top vs. htop in linux: A Detailed Comparison
- 12. 20 Frequently Asked Questions (FAQs)
1. What is htop in linux?
htop command in linux is an open-source system monitor that is based on Ncurses.
It provides an interactive, full-screen experience, which sets it apart from its predecessor. In addition to allowing mouse usage while interacting with the tool, you can also scroll horizontally to view the complete command path for each process.
It provides a method of process management (process termination and process prioritization) without requiring you to remember the Process IDs (PIDs).
To many people who are just getting started, htop command in linux represents the “Task Manager” of their desktop. To the more experienced user, htop represents a means by which to quickly identify and correct issues such as memory leaks, zombie processes, and CPU bottlenecks.
2. How to Install htop in linux (All Distributions)
Unlike the procps package for kernels, htop command in Linux is often installed quickly by following these directions on any popular OS distribution:
Ubuntu/Debian/Mint:
- You can install htop via:
sudo apt-get update && sudo apt-get install htop
Fedora/Cent OS/AlmaLinux/Unix:
- For enterprise/Unix-based systems, the EPEL (Extra Packages for Enterprise Linux) repository must first be enabled before installing htop. You can do this by:
sudo dnf install epel-release -ysudo dnf install htop -y
Arch Linux/Unix:
- Arch users can install htop through the Pacman package manager (and optionally via your package manager):
sudo pacman -S htop
macOS:
- If running on MacOS, use the Homebrew package manager to install htop:
brew install htop
3. Understanding the Dashboard Architecture
htop opens with a visually appealing interface divided into 3 primary segments when it first appears, making it easy to determine immediately if one or more of your computer’s resources need checking. The following summary will show you how to navigate through the 3 sections of htop:
The Header Area (Top Left):
Contains CPU vital signs for each individual core, including percentage of RAM being used and amount of Swap space being utilized.
The System Summary Area (Top Right):
Shows all tasks running on the system, as well as average system load for the last 1 minute, 5 minutes, and 15 minutes, and also displays the amount of time the system has been running.
The Process List Area (Center):
Contains a complete list of all active processes running on the machine, sorted descending order by CPU usage.
The Footer (Bottom Bar):
Represents a descriptive key that indicates what each of the function keys (F1-F10) can do to help diagnose problems with your machine.
5. The Process Table: Every Column Explained
To use htop command in linux effectively, you must understand the data columns in the main table:
| Field | Full Name | What it Measures |
|---|---|---|
| PID | Process ID | The unique number identifying the task. |
| USER | Owner | The user account running the process. |
| PRI | Priority | The kernel’s internal priority for the task. |
| NI | Nice Value | The user-defined priority (-20 to 19). |
| VIRT | Virtual Memory | Total memory address space the process is using. |
| RES | Resident Memory | Actual Physical RAM the process is using. |
| SHR | Shared Memory | Memory that can be shared with other apps. |
| S | Status | R (Running), S (Sleeping), Z (Zombie), T (Stopped). |
| CPU% | CPU Usage | The percentage of a single core the process is using. |
| MEM% | RAM Usage | The percentage of total RAM the process is using. |
6. Mastering Interactive Keyboard Shortcuts
The true function of htop command in linux is based primarily on its “hotkeys”, using what would usually be complex command line prompts or long commands, involves only pressing one button:
Space:
When tagged, one can easily kill multiple processes all at once, as opposed to writing out each command for every process.
U:
Allows for removing any process that has been previously tagged.
l:
Lists all files and directories currently being used by the selected process (requires lsof).
s:
Tracing a process to check for any system calls that have been made by the process (requires strace).
This feature will allow for debugging of an application that is frozen due to a lack of response.
F5 or Directly Click on t:
Allows to opening/hiding in a tree view format all processes spawned by Chrome or Nginx and their child processes.
7. Advanced Sorting and Filtering Techniques
When there are 500 processes running, it can be very difficult to determine which one of those is causing lag on your system. htop command in linux provides 3 different ways of finding that information:
1. Searching (F3)
If you press F3 and then type in the name of the application, htop will jump to the first instance of that application. If you press F3 again, htop will jump to the next instance of that application.
2. Filtering (F4)
Filtering is significantly more powerful than searching. If you press F4 and then enter a keyword, htop will hide all processes that do not match. Filtering gives you a much clearer view of what processes are running based on a keyword or phrase.
3. Sorting (F6)
In addition to having to know to press Shift+M or Shift+P to sort processes in top, with htop, you can simply press F6 and select from a list of sorting options: memory, user, etc. You can also choose to sort processes by when they started.
8. Managing Tasks: Killing and Renicing Processes
Using the “Signal” menu in htop on Linux allows you to stop a process without having to exit.
You can highlight the process by using the arrow keys.
To send a signal to the highlighted process, press F9.
Once you press F9, a sidebar will appear on the left side of the screen, listing all the Unix signals.
SIGTERM (15) is the “Nice” way to stop a process, allowing the application to save any required data.
SIGKILL (9) is the “Hard” way to stop a process immediately and without regard for any work being done by the application.
If a process is consuming excessive CPU resources and you do not wish to kill it but instead want to reduce its impact on other processes, you can use F7 (Increase Priority) or F8 (Decrease Priority) to change the priority of the application. The process is made “nicer” to other processes by assigning it a higher NI value.
9. Customizing the htop Interface (F2 Menu)
You can configure various settings for htop by pressing F2. As of this writing, the Setup Menu allows for the following configurations:
Meters
You may add one of three meters, which are either Clock, Battery, or Hostname to the header.
Display Options
You may enable Tree View as default, or arrange your view and hide threads in order to declutter your list.
Colour
A number of colour preset options are available; they include: Monochrome, Solarized, and Night.
Columns
Using the columns option, you may also add a Processors column which will show you which process is running on which core from the list of cores (0, 1, 2 ,3) currently being used by processes.10. Real-World Troubleshooting with htop in linux
Scenario A: The Frozen Application
In the HTop program on a Linux-based computer, check the process list to see if any of them are in the D (Uninterruptible Sleep) state. This generally indicates that those processes are trying to access either a damaged disk or an inaccessible network share.
Scenario B: The OOM (Out Of Memory) Killer
If your server crashes, the usage level of Swap memory, as observed in HTop, is critical. Once Swap memory is exhausted, the Linux-Kernel will randomly terminate processes in order to protect its available memory. Use HTop to locate “RAM hogs” before this situation occurs.
11. Top vs. htop in linux: A Detailed Comparison
Is it worth installing? Let’s look at the numbers:
| Feature | Top | htop in linux |
|---|---|---|
| Visual Appeal | Text Only | Color Graphs |
| Navigation | Keyboard only | Mouse & Keyboard |
| Horizontal Scroll | No | Yes |
| Tree View | Complex to enable | One-click (F5) |
| Installation | Built-in | Separate package |
12. 20 Frequently Asked Questions (FAQs)
1. How do I exit htop in linux?
Press F10 or simply the q key.
2. Why is my htop in linux black and white?
Your terminal may not support colors, or you need to change the color scheme in the F2 menu.
3. Can I use htop to monitor remote servers?
Yes, just SSH into the server and run htop as you would locally.
4. How do I see hidden kernel threads?
Press K (Capital K) to toggle the visibility of kernel tasks.
5. What is the difference between VIRT and RES?
VIRT is all the memory a process can see; RES is the actual RAM it is using right now.
6. Does htop in linux show GPU usage?
Standard htop does not. You would need a tool like nvtop or intel-gpu-tools.
7. How do I see the full path of a command?
Use the Right Arrow key to scroll horizontally.
8. Why can’t I kill a process?
You may need root privileges. Try running sudo htop.
9. How do I change the refresh rate?
Use htop -d [delay]. For example, htop -d 10 refreshes every 1 second.
10. Can htop save my settings?
Yes, settings are saved to ~/.config/htop/htoprc automatically.
11. How do I find a process by its PID?
Press F3 and type the PID number.
12. What does a “Zombie” (Z) state mean?
The process is finished, but its parent hasn’t acknowledged it yet. They don’t use RAM, but they take up a slot in the PID table.
13. Can I display the hostname in the header?
Yes, enable it in the F2 > Meters menu.
14. How do I see how much CPU each thread is using?
Press H to show or hide user threads.
15. What is “Load Average”?
The number of processes in the “run queue.” High load with low CPU usage usually means disk lag.
16. How do I sort by User?
Press F6 and select USER from the list.
17. Does htop work on ARM processors (like Raspberry Pi)?
Yes, it works perfectly on all architectures including x86, ARM, and RISC-V.
18. How do I highlight multiple processes?
Hover over a process and press Space.
19. Can I change the unit size (e.g., MB to GB)?
htop scales units automatically based on the size of the data.
20. Why should I use htop in linux instead of a GUI monitor?
It uses fewer resources, works over SSH, and is faster to navigate for power users.
Conclusion
While htop in Linux is a graphical representation (and improvement) over the standard “top” command in Linux, it can also help identify how much processing power a given application uses on a machine (or all machines in a cluster). Since the layout and functionality of the meters differ from the more familiar standard “top” functionality, learning how to customize these meters will allow you to monitor your systems with more detail and accuracy than ever before.
For instance, if you have a server that is slow because of too many CPU cycles being consumed by one or more applications (for example, when compiling complex code) and want to improve the responsiveness of that server, using “htop” to determine what components are causing the slow down will provide you with the knowledge needed to take appropriate action.
If you are new to Linux, this guide on basic Linux commands for beginners will help you understand the terminal step by step.
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