The requested URL was not found - permalink error

When I update the permalinks to anything but default, links in the site give the error The requested URL ### was not found on this Server.

Enable rewrite_module in apache


Introduction

In this tutorial, we will activate and learn how to manage URL rewrites using Apache2's mod_rewrite module. This tool allows us to rewrite URLs in a cleaner fashion, translating human-readable paths into code-friendly query strings.

This guide is split into two halves: the first sets up a sample web application and the second explains commonly-used rewrite rules.

Prerequisites

To follow this tutorial, you will need:

• One fresh Ubuntu 14.04 Droplet
• A sudo non-root user, which you can set up by following steps 2 and 3 of this tutorial

Step 1 — Installing Apache

In this step, we will use a built-in package installer called apt-get. It simplifies management drastically and facilitates a clean installation.

First, update the system's package index. This will ensure that old or outdated packages do not interfere with the installation.

sudo apt-get update  

Apache2 is the aforementioned HTTP server and the world's most commonly used. To install it, run the following:

sudo apt-get install apache2  

For information on the differences between Nginx and Apache2, the two most popular open-source web servers, see this article.

Step 2 — Enabling mod_rewrite

Now, we need to activate mod_rewrite.

sudo a2enmod rewrite  

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

sudo service apache2 restart  

Step 3 — Setting Up .htaccess

In this section, we will setup a .htaccess file for simpler rewrite rule management.

A .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.

We will need to set up and secure a few more settings before we can begin.

First, allow changes in the .htaccess file. Open the default Apache configuration file using nano or your favorite text editor.

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

Inside that file, you will find the <VirtualHost *:80> block on line 1. Inside of that block, add the following block:

/etc/apache2/sites-available/default
<Directory /var/www/html>                  Options Indexes FollowSymLinks MultiViews                  AllowOverride All                  Order allow,deny                  allow from all  </Directory>  

Your file should now match the following. Make sure that all blocks are properly indented.

/etc/apache2/sites-available/default
<VirtualHost *:80>      <Directory /var/www/html>            . . .        </Directory>        . . .  </VirtualHost>  

To put these changes into effect, restart Apache.

sudo service apache2 restart  

Now, create the .htaccess file.

sudo nano /var/www/html/.htaccess  

Add this first line at the top of the new file to activate the RewriteEngine.

/var/www/html/.htaccess
RewriteEngine on  

Save and exit the file.

To ensure that other users may only read your .htaccess, run the following command to update permissions.

sudo chmod 644 /var/www/html/.htaccess  

You now have an operational .htaccess file, to govern your web application's routing rules.