Entity tags (ETags) are a mechanism that web servers and browsers use to validate cached components. The server generates and sends an ETag value, which is a token representing a specific version of a component, to the client when the component is initially sent. For subsequent requests, the client sends back the ETag value to check if the resource has changed. If it hasn’t, the server can send a 304 Not Modified status, saving bandwidth.
In an environment with multiple servers, like a load-balanced setup, ETag values generated on one server may not match the values generated on another server for the same resource. Therefore, unless your servers are properly configured to generate identical ETags, it’s often recommended to disable them.
In this article, we will provide a step-by-step guide on how to disable ETags in an Apache web server. The process involves editing your Apache server’s configuration files, so make sure you have the necessary permissions to do so.
Steps to Disable ETags in Apache
1. Backup your Current Configuration
Before making any changes, it’s always wise to backup your current configuration. Locate the Apache configuration file – typically named httpd.conf or apache2.conf. Its exact location depends on your system; for example, on Ubuntu, you may find it in /etc/apache2/apache2.conf. Once found, create a backup:
sudo cp /etc/apache2/apache2.conf /etc/apache2/apache2.conf.bak
Replace /etc/apache2/apache2.conf with your configuration file’s actual location.
2. Open the Configuration File
Next, open the configuration file with your preferred text editor. For instance, to open it with nano, use:
sudo nano /etc/apache2/apache2.conf
3. Add the FileETag Directive
In the configuration file, search for a suitable section to add the FileETag directive. A common choice is within the <Directory> block that configures your web document root.
To disable ETags entirely, set the FileETag directive to None:
For example, your <Directory> block might look like this:
Options Indexes FollowSymLinks
Require all granted
If you want to disable ETags for specific file types only, use the <FilesMatch> block. For example, to disable ETags for JPEG and PNG images:
4. Save Changes and Close the File
After editing the configuration file, save your changes and close it. In nano, you can do this by pressing `Ctrl+X`, then `Y` to confirm saving changes, and finally Enter to confirm the file name.
5. Test the Configuration
Before you restart the Apache server, it’s good practice to test your configuration for syntax errors. Use the Apache’s configtest utility:
sudo apachectl configtest
If the output says Syntax OK, your configuration changes have no syntax errors.
6. Restart Apache Server
Finally, to apply your changes, restart the Apache server. On Ubuntu, use:
sudo systemctl restart apache2
On CentOS or Fedora, use:
sudo systemctl restart httpd
Disabling ETags in an Apache server can be a simple process when done correctly. However, always remember to backup your configurations before making any changes to avoid disrupting your server’s functionality. By following the steps provided in this guide, you should be able to disable ETags successfully.