How to Rewrite URLs with mod_rewrite for Apache on Ubuntu 18.04

Introduction

Apache’s mod_rewrite module lets you rewrite URLs in a cleaner fashion, translating human-readable paths into code-friendly query strings. It also lets you rewrite URLs based on conditions.

An .htaccess file lets you create and apply rewrite rules without accessing server configuration files. By placing the .htaccess file in the root of your web site, you can manage rewrites on a per-site or per-directory basis.

In this tutorial, you’ll enable mod_rewrite and use .htaccess files to create a basic URL redirection, and then explore a couple of advanced use cases.

Prerequisites

To follow this tutorial, you will need:

• One Ubuntu 18.04 server set up by following the Ubuntu 18.04 initial server setup guide, including a sudo non-root user and a firewall.

• Apache installed by following Step 1 of How To Install Linux, Apache, MySQL, PHP (LAMP) stack on Ubuntu 18.04.

Step 1 — Enabling mod_rewrite

In order for Apache to understand rewrite rules, we first need to activate mod_rewrite. It’s already installed, but it’s disabled on a default Apache installation. Use the a2enmod command to enable the module:

sudo a2enmod rewrite

This will activate the module or alert you that the module is already enabled. To put these changes into effect, restart Apache.

sudo systemctl restart apache2

mod_rewrite is now fully enabled. In the next step we will set up an .htaccess file that we’ll use to define rewrite rules for redirects.

Step 2 — Setting Up .htaccess

An .htaccess file allows us to modify our rewrite rules without accessing server configuration files. For this reason, .htaccess is critical to your web application’s security. The period that precedes the filename ensures that the file is hidden.

Note: Any rules that you can put in an .htaccess file can be also put directly into server configuration files. In fact, the official Apache documentation recommends using server configuration files instead of .htaccess because Apache processes it faster that way.

However, in this simple example, the performance increase will be negligible. Additionally, setting rules in .htaccess is convenient, especially with multiple websites on the same server. It does not require a server restart for changes to take effect and it does not require root privileges to edit those rules, simplifying maintenance and and making changes possible with unprivileged account. Some popular open-source software, like Wordpress and Joomla, often relies on an .htaccess file for the software to modify and create additional rules on demand.

Before you start using .htaccess files, you’ll need to set up and secure a few more settings.

By default, Apache prohibits using an .htaccess file to apply rewrite rules, so first you need to allow changes to the file. Open the default Apache configuration file using nano or your favorite text editor.

sudo nano /etc/apache2/sites-available/000-default.conf

Inside that file, you will find a <VirtualHost *:80> block starting on the first line. Inside of that block, add the following new block so your configuration file looks like the following. Make sure that all blocks are properly indented.

/etc/apache2/sites-available/000-default.conf

<VirtualHost *:80>
    <Directory /var/www/html>
        Options Indexes FollowSymLinks MultiViews
        AllowOverride All
        Require all granted
    </Directory>

    . . .
</VirtualHost>

Save and close the file. To put these changes into effect, restart Apache.

sudo systemctl restart apache2

Now, create an .htaccess file in the web root.

sudo nano /var/www/html/.htaccess

Add this line at the top of the new file to activate the rewrite engine.

/var/www/html/.htaccess

RewriteEngine on

Save the file and exit.

You now have an operational .htaccess file which you can use to govern your web application’s routing rules. In the next step, we will create sample website files that we’ll use to demonstrate rewrite rules.

Step 3 — Configuring URL Rewrites

Here, we will set up a basic URL rewrite which converts pretty URLs into actual paths to pages. Specifically, we will allow users to access http://your_server_ip/about, but display a page called about.html.

Begin by creating a file named about.html in the web root.

sudo nano /var/www/html/about.html

Copy the following HTML code into the file, then save and close it.

/var/www/html/about.html

<html>
    <head>
        <title>About Us</title>
    </head>
    <body>
        <h1>About Us</h1>
    </body>
</html>

You can access this page at http://your_server_ip/about.html, but notice that if you try to access http://your_server_ip/about, you will see a 404 Not Found error. To access the page using /about instead, we’ll create a rewrite rule.

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