How to Setup Siege to Perform a Stress Test on Linux (Ubuntu and CentOS)

How to Setup Siege to Stress Test a Web Server

In web hosting, understanding how your web server reacts under heavy load is crucial. This knowledge allows you to make informed decisions about scaling, optimizing, and ensuring the best user experience.

One of the tools that can aid in this endeavor is Siege. Siege is a versatile HTTP load testing and benchmarking utility that can simulate multiple users accessing a website simultaneously. By using it, you can identify potential bottlenecks and performance issues in your server setup.

In this tutorial, we will guide you through the process of setting up Siege on two popular Linux distributions: Ubuntu and CentOS. We will also provide insights into how to effectively use this tool to stress test your server.

Let’s get started.

Step 1: Installation

– Ubuntu

Update the System:

sudo apt update && sudo apt upgrade -y

Install Siege:

sudo apt install siege -y

– CentOS

Install EPEL Repository:

sudo yum install epel-release -y

Install Siege:

sudo yum install siege -y

Step 2: Configuring Siege

Backup the Default Configuration (Optional but recommended):

cp /etc/siege/siegerc ~/.siegerc

Edit the Configuration:

nano ~/.siegerc

Within the configuration file, you’ll encounter various parameters that dictate how Siege operates. Here are some of the most commonly adjusted parameters, along with explanations and example scenarios:

  • verbose = true: This setting controls whether Siege displays a lot of information (verbose mode) or minimal information during its operation. If you’re troubleshooting an issue or want detailed insights into the stress test, you might set this to true. For regular tests where you only need a summary, you might set it to false.
  • concurrent = 25: This sets the default number of simulated users. In this example, 25 users will be simulated. If you’re testing how your website performs under typical daily traffic, you might set this to a number that reflects average concurrent users. For peak traffic scenarios, you’d increase this number.
  • delay = 1: This sets the delay between requests by each simulated user. The delay is in seconds. If you want to simulate users who are browsing at a leisurely pace, reading content before moving to the next page, you might set a delay of a few seconds.
  • benchmark = false: When set to true, Siege operates in benchmark mode, sending requests as quickly as possible. If you’re conducting a performance benchmark to see the maximum requests per second your server can handle, you’d set this to true.
  • internet = false: This setting, when enabled, causes Siege to choose URLs randomly from the provided list, simulating real-world internet traffic. If you have a list of multiple URLs and you want to simulate random access patterns like real users might exhibit, you’d set this to true.
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Example Scenario for Configuration Adjustments

Imagine you’re preparing for a Black Friday sale on your e-commerce website. You expect a significant increase in traffic, with users browsing products, adding them to carts, and checking out.

To simulate this:

  • Increase the concurrent parameter to a high number, say 500, to simulate many users accessing the site at once.
  • Set a delay of 2-3 seconds, simulating users spending some time on each page.
  • Enable internet = true if you have a list of various product pages, cart pages, and checkout pages to simulate users accessing different parts of the site randomly.
  • After adjusting these parameters, save the configuration file and then run Siege to see how your server performs under these simulated conditions.

Step 3: Running a Stress Test

Simple Test:

siege -c 50 -t1M

This command instructs Siege to perform a stress test on the specified website, in our case,

** Preparing 50 concurrent users for battle.
The server is now under siege for 1 minute(s)...
Lifting the server siege...
Transactions:		        6050 hits
Availability:		      100.00 %
Elapsed time:		       59.44 secs
Data transferred:	       83.72 MB
Response time:		        0.48 secs
Transaction rate:	      101.75 trans/sec
Throughput:		        1.41 MB/sec
Concurrency:		       48.84
Successful transactions:   6050
Failed transactions:	       0
Longest transaction:	       1.03
Shortest transaction:	       0.26

The parameters used in the command are:

  • -c 50: This specifies the concurrency level, meaning 50 users will be simulated to access the website simultaneously.
  • -t1M: This sets the duration of the test. The test will run for 1 minute. The ‘M’ stands for minutes. You can also use ‘H’ for hours and ‘S’ for seconds.

Imagine you’ve just deployed a new feature on your website and you want to ensure that the server can handle 50 users browsing the site at the same time. By running this command, you can simulate this scenario and observe how the server responds. This can help in identifying any potential bottlenecks or issues that might arise when multiple users access the site concurrently.


siege -b -c 100 -t2M

This command is a bit more intensive and is designed to benchmark the website’s performance.

** Preparing 100 concurrent users for battle.
The server is now under siege in benchmark mode for 2 minute(s)...
Lifting the server siege...
Transactions:		       12050 hits
Availability:		      100.00 %
Elapsed time:		      119.88 secs
Data transferred:	      166.42 MB
Response time:		        0.45 secs
Transaction rate:	      100.54 trans/sec
Throughput:		        1.39 MB/sec
Concurrency:		       45.24
Successful transactions:  12050
Failed transactions:	       0
Longest transaction:	       0.98
Shortest transaction:	       0.23

The parameters used are:

  • -b: This puts Siege in benchmark mode, meaning it will send requests as fast as possible without any delay between them. It’s a way to push the server to its limits.
  • -c 100: This sets the concurrency level to 100, simulating 100 users accessing the website simultaneously.
  • -t2M: This sets the duration of the test to run for 2 minutes.
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Suppose you’re expecting a surge in traffic due to an upcoming marketing campaign. Before the campaign goes live, you want to ensure that your server can handle a large number of users accessing the site without any hiccups. By running this benchmarking test, you can simulate a high-traffic scenario and gauge the server’s performance. If the server struggles during the test, it might be an indication that you need to optimize your server configurations or even consider scaling up your server resources.

Additional Tips

  • Monitoring Tools: While Siege provides insights into how your server performs under stress, it’s equally important to monitor server health in real-time. Tools like htop, netstat, and iostat can provide valuable insights.
  • Optimization: Based on the results from Siege, you might need to optimize your server. This could involve tweaking server configurations, optimizing databases, or even upgrading server hardware.
  • Security: While stress testing, ensure that you’re not unintentionally launching a Denial of Service (DoS) attack on someone else’s server. Always have permission to test, especially if the server isn’t owned by you.
  • Regular Testing: Server environments and web applications evolve. Regularly stress testing your server, especially after significant changes or updates, ensures consistent performance.
  • Backup: Before making any significant changes based on your Siege test results, always backup your server configurations and data. This ensures you can revert to a previous state if something goes wrong.

Commands Mentioned

  • sudo apt update && sudo apt upgrade – Updates the package list and upgrades the packages on Ubuntu.
  • sudo apt install siege – Installs Siege on Ubuntu.
  • sudo yum install epel-release – Installs the EPEL repository on CentOS.
  • sudo yum install siege – Installs Siege on CentOS.
  • siege -c 50 -t1M – Runs a stress test with 50 users for 1 minute.
  • htop – Provides a real-time view of system processes, CPU, memory, and more.
  • netstat – Displays network connections, routing tables, and network interface statistics.
  • iostat – Monitors system input/output device loading by observing the time devices are active in relation to their average transfer rates.
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  1. What is Siege used for?

    Siege is an HTTP load testing and benchmarking utility. It is designed to simulate multiple users accessing a website simultaneously to help webmasters identify potential bottlenecks and performance issues in their server setup.

  2. How do I increase the number of simulated users in Siege?

    You can increase the number of simulated users in Siege using the ‘-c’ option followed by the number of users. For example, ‘-c 100’ simulates 100 users.

  3. Can I run Siege on other Linux distributions?

    Yes, Siege can be installed and run on various Linux distributions. The installation process might differ slightly based on the package manager of the distribution.

  4. Is Siege suitable for testing other types of servers?

    While Siege is primarily designed for HTTP load testing, it can be used to test other types of servers that communicate over HTTP/HTTPS. However, for specialized servers, dedicated testing tools might be more appropriate.

  5. How do I interpret the results of a Siege test?

    Siege provides various metrics after a test, including the number of hits, bytes transferred, response time, concurrency, and more. These metrics help in understanding server performance, response times, and potential bottlenecks.


Understanding server performance under stress is vital for ensuring optimal user experience and making informed decisions about scaling and optimization. Siege offers a robust solution for webmasters and server administrators to simulate real-world load scenarios and identify potential issues. By following this tutorial, you’ve equipped yourself with the knowledge to set up and utilize Siege on both Ubuntu and CentOS.

As you continue to manage and optimize your server environment, consider exploring more about different hosting solutions like dedicated server, VPS server, cloud hosting, and shared hosting. Each hosting solution offers unique advantages tailored to different needs, and understanding them can further enhance your server management skills.

For a deeper dive into web servers, you might want to explore guides on best server software, Apache, Nginx, and LiteSpeed

Feel free to share your experiences, challenges, or any additional tips in the comments section below.


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