Apache Mod Rewrite

Mastering Redirection with `mod_rewrite` in Apache

If you are managing a website that requires redirecting traffic from one domain to another while preserving access to certain paths, mod_rewrite in Apache can be your best friend. In this post, we will tackle how to redirect all requests except one specific path, such as /audio, using mod_rewrite.

The Problem

Many webmasters find themselves in a situation where they need to redirect traffic to a new domain, but want to allow specific requests to go through without change. For instance, if you are transitioning from mydomain.example to newdomain.example, and you want all traffic redirected except requests for /audio, that’s where mod_rewrite comes in.

Common Syntax Issues

The original attempt made by a user to set up redirection included a complex use of regular expressions and advanced conditions. While the intention was correct, using the HTTP_HOST in the RewriteCond was misguided since it doesn’t include the request path.

The Solution

To achieve the desired redirection while allowing access to the /audio path, your Apache configuration should be adjusted as follows:

Step-by-Step Configuration

Activate the Rewrite Engine: First, make sure that the rewrite engine is turned on.
```
RewriteEngine on
```
Set Up the Condition: Use the REQUEST_URI variable to check if the request is NOT for the /audio path.
```
RewriteCond %{REQUEST_URI} !^/audio
```
Define the Rewrite Rule: Create a rule that handles the redirection to the new domain.
```
RewriteRule ^(.*)$ http://www.newdomain.example [L,R=301]
```

Putting It All Together

In your VirtualHost configuration, it should look something like this:

<VirtualHost *:80>
    ServerAdmin me@mydomain.example
    DocumentRoot "/var/www/mydomain.example/htdocs"
    ServerName www.mydomain.example
    ServerAlias mydomain.example

    RewriteEngine on
    RewriteCond %{REQUEST_URI} !^/audio
    RewriteRule ^(.*)$ http://www.newdomain.example [L,R=301]

    RewriteLog /path/to/log/file
    RewriteLogLevel 3

    ErrorLog logs/error_log
    CustomLog logs/access_log common
</VirtualHost>

Debugging Your Configuration

If you still encounter issues after setting this up, consider enabling logging to see the conditions and rules in action:

Use the RewriteLog to specify a log file and set the log level high enough to capture relevant details.

RewriteLog /path/to/log/file
RewriteLogLevel 3

Understanding the Logs

When you check the logs after implementing the above rules, ensure that requests to /audio do not hit the rewrite rule.

Conclusion

Setting up URL redirection using mod_rewrite is a powerful way to manage traffic while ensuring specific paths remain accessible. By focusing on the correct configuration and understanding the behavior of REQUEST_URI, you can solve issues related to unwanted redirects effectively.

With this guidance, you’re now equipped to handle URL redirections in Apache with confidence. Happy coding!

Mastering Redirection with mod_rewrite in Apache