Stress Command Examples

Comprehensive Guide to Stress Utility: Performance Testing and Load Generation

Overview

The Stress utility is a powerful workload generator tool designed to simulate high-load conditions on Linux servers. It allows system administrators and developers to test system performance, stability, and resource management under various stress scenarios.

Installation

Centos/RHEL

# Enable EPEL repository (for Amazon Linux)
$ sudo yum install amazon-linux-extras install epel -y

# Install Stress
$ sudo yum install stress -y

Ubuntu/Debian

$ sudo apt-get update
$ sudo apt-get install stress -y

Basic Stress Command Examples

1. CPU Stress

Generate load on multiple CPU cores:

# Spawn 4 workers that perform square root calculations
$ stress -c 4

# Spawn 8 CPU workers
$ stress -c 8

# Run CPU workers in background
$ stress -c 8 &

2. Memory Stress

Create memory allocation stress:

# Allocate 1GB of memory with 2 workers
$ stress -m 2 --vm-bytes 1G

# Allocate 2GB of memory with 4 workers
$ stress -m 4 --vm-bytes 2G

# Perform memory writes
$ stress -m 4 --vm-bytes 2G --vm-method write

3. I/O Stress

Generate I/O load:

# 3 workers performing disk I/O
$ stress -i 3

# Combine CPU and I/O stress
$ stress -c 4 -i 2

4. Comprehensive System Stress

Create multi-dimensional load:

# 4 CPU workers, 2 memory workers, 1 I/O worker
$ stress -c 4 -m 2 -i 1

# Long-running stress test (30 minutes)
$ stress -c 4 -m 2 -i 1 --timeout 1800

5. Watching System Load

Monitor system load during stress test:

# Before stress test
$ uptime
 04:12:18 up 182 days, load average: 3.27, 0.94, 0.36

# During stress test
$ uptime
 04:13:59 up 182 days, load average: 8.66, 3.45, 1.32

Advanced Options

Timeout Control

Limit stress test duration:

# Run stress for 15 minutes (900 seconds)
$ stress -c 4 --timeout 900

Verbose Mode

Get detailed information:

# Verbose output
$ stress -v -c 4

Best Practices

Start Small: Begin with fewer workers and gradually increase load.
Monitor System: Use top, htop, or uptime to track resource usage.
Controlled Environment: Test during maintenance windows.
Backup Critical Data: Always have backups before stress testing.

Potential Risks

Excessive stress can temporarily freeze or crash systems
Not recommended on production servers without careful planning
May impact other running services

Troubleshooting

If stress fails, ensure you have sufficient system resources
Check kernel support for stress-ng features
Verify package installation

Alternatives

stress-ng: More advanced stress testing utility
sysbench: Scriptable database and system performance benchmark
dd: Simple I/O performance testing

Conclusion

Stress utility provides a flexible way to simulate system load, helping administrators and developers understand system behavior under pressure.