How to Impose High CPU Load and Stress Test on Linux

stress-ng, an extended version of stress, goes beyond the basic functionalities of its predecessor.
To install stress on Linux, use the following appropriate command for your specific Linux distribution.
As recommended, these tools should be used with superuser privileges due to their significant impact on system resources.

• Fine-tune system activities and optimize configurations.
• Monitor operating system kernel interfaces under load.
• Test Linux hardware components such as CPU, memory, disk devices, and more to observe their performance under stress.
• Measure different power-consuming loads and their impact on the system.

Linux Stress Testing Tools: stress and stress-ng

Understanding how your systems perform under stress helps you make informed decisions about capacity planning, hardware upgrades, and system optimization.

stress Tool

uptime
sudo stress-ng –cpu 4 –io 4 –vm 1 –vm-bytes 1G –timeout 60s –metrics-brief
uptime

Real-World Use Cases for Stress Testing in Linux

uptime
sudo stress –cpu 8 –timeout 20
uptime

2. CPU Stress Test with Verbose Output

sudo stress-ng –cpu 0 –vm 2 –vm-bytes 80% –timeout 10m –metrics-brief

uptime
sudo stress –cpu 4 –io 3 –vm 2 –vm-bytes 256M –timeout 20s
uptime

How to Install ‘stress-ng’ Tool in Linux

Simulate production workload patterns to test system stability before deploying new applications:

How to Install ‘stress’ Tool in Linux

uptime
sudo stress –vm 1 –timeout 60s
uptime

4. Combined Stress Test (CPU, I/O, and Memory)

It provides a wider range of stress tests, covering not only CPU, memory, I/O, and disk stress but also incorporating additional tests for things like inter-process communication, sockets, and various file operations.
sudo apt install stress-ng [On Debian, Ubuntu and Mint]
sudo yum install stress-ng [On RHEL/CentOS/Fedora and Rocky/AlmaLinux]
sudo emerge -a sys-apps/stress-ng [On Gentoo Linux]
sudo apk add stress-ng [On Alpine Linux]
sudo pacman -S stress-ng [On Arch Linux]
sudo zypper install stress-ng [On OpenSUSE]
sudo pkg install stress-ng [On FreeBSD]

uptime
sudo stress –cpu 8 -v –timeout 30s
uptime

3. Virtual Memory Stress Test

Both stress and stress-ng contribute significantly to the proactive management of Linux systems, enabling administrators and programmers to optimize system configurations, identify potential issues, and enhance overall system reliability.
sudo apt install stress [On Debian, Ubuntu and Mint]
sudo yum install stress [On RHEL/CentOS/Fedora and Rocky/AlmaLinux]
sudo emerge -a sys-apps/stress [On Gentoo Linux]
sudo apk add stress [On Alpine Linux]
sudo pacman -S stress [On Arch Linux]
sudo zypper install stress [On OpenSUSE]
sudo pkg install stress [On FreeBSD]

uptime
sudo stress-ng –hdd 5 –hdd-ops 100000
uptime

4. Combined Stress Test (CPU, I/O, and Virtual Memory)

After upgrading RAM, CPU, or storage, verify that the new hardware is functioning correctly:
sudo stress-ng –cpu 4 –cpu-load 75 –vm 2 –vm-bytes 2G –timeout 30m

stress is a simple yet powerful tool designed to impose a configurable amount of CPU, memory, I/O, or disk stress on a Linux system and, by simulating heavy workloads, allows administrators to observe how the system responds under pressure.
sudo stress-ng –cpu 0 –io 4 –hdd 2 –timeout 5m –verify

Next, run the stress command to spawn 8 workers spinning on sqrt() with a timeout of 20 seconds. After running stress, check the uptime again and compare the load average.

• To start N instances of each stress test, use the --all N option as follows.
• To start N processes to exercise the CPU by sequentially working through all the different CPU stress testing methods, use the --cpu N option as follows.
• To use a given CPU stress testing method, use the --cpu-method option. There are many methods available that you can use, to view the manpage to see all the methods to use.
• To stop the CPU stress process after N bogo operations, use the --cpu-ops N option.
• To start N I/O stress testing processes, use the --io N option.
• To stop io stress processes after N bogo operations, use the --io-ops N option.
• To start N vm stress testing processes, use the --vm N option.
• To specify the amount of memory per vm process, use the --vm-bytes N option.
• To stop vm stress processes after N bogo operations, use --vm-ops N options
• Use the --hdd N option to start N harddisk exercising processes.
• To stop hdd stress processes after N bogo operations, use the --hdd-ops N option.
• You can set a timeout after N seconds by using the --timeout N option.
• To generate a summary report after bogo operations, you can use --metrics or --metrics-brief options. The --metrics-brief displays non-zero metrics.
• You can also start N processes that will create and remove directories using mkdir and rmdir by using the --dir N option.
• To stop directory operations processes use --dir-ops N options.
• To start N CPU consuming processes that will exercise the present nice levels, include the --nice N option. When using this option, every iteration will fork off a child process that runs through all the different nice levels running a busy loop for 0.1 seconds per level, and then exits.
• To stop nice loops, use the --nice-ops N option as follows.
• To start N processes that change the file mode bits via chmod(2) and fchmod(2) on the same file, use the --chmod N option. Remember the greater the value for N then the more contention on the file. The stressor will work through all the combinations of mode bits that you specify with chmod(2).
• You can stop chmod operations by the --chmod-ops N option.
• You can use the -v option to display more information about ongoing operations.
• Use -h to view help for stress-ng.

How to Use ‘stress-ng’ on Linux Systems

sudo stress option argument

Both stress and stress-ng are excellent tools for general System Administration tasks in Linux environments.
The following are a few stress-ng test example commands to get started:
As a System Administrator, examining and monitoring how your Linux systems perform under heavy workloads is crucial for maintaining optimal performance and reliability.
uptime
sudo stress-ng –cpu 4 –cpu-method fft –timeout 2m
uptime

3. Hard Drive Stress Test

Stress testing provides System Administrators and Programmers with valuable insights to:

1. Load Testing Before New Server Deployment

stress and stress-ng are essential tools for assessing and testing the performance of Linux systems under various conditions.
uptime
sudo stress-ng –cpu 8 –timeout 60 –metrics-brief
uptime

2. Specific CPU Method Test (FFT)

To examine the effect of stress testing, first run the uptime command to note the load average.
Before putting a new server into production, run comprehensive stress tests to ensure it can handle expected workloads, which will help you identify hardware issues early:

3. Reproducing Production Load

Here are a few example commands to get started with stress:
In this guide, we will explore two important tools, stress and stress-ng, for conducting comprehensive stress tests on your Linux systems.

Summary

I hope this guide was useful. If you have any additional ideas on how to test the health status of your system using these tools or any other stress testing utilities, feel free to share your thoughts in the comments below.
To run 8 CPU stressors with a timeout of 60 seconds and a summary at the end of operations.
sudo stress-ng option argument

This tool is valuable for identifying potential weaknesses and ensuring that the system can handle demanding tasks without compromising performance.