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How to Configure Apache as a Reverse Proxy with mod_proxy

Author: Humphrey Mpairwe

Last Updated: Wed, May 25, 2022
Web Servers

Introduction

Apache is a web server application that can serve dynamic web content or act as a reverse proxy —forwarding client requests to back-end applications. This article explains how to configure Apache to work as a reverse proxy with mod_proxy.

This guide proxies an ownCloud application on port 8080 under Docker, but you can use the same technique to host another application on a different port.

Prerequisites

A Ubuntu 20.04 server is used in this article, but these instructions work for any Linux server running Apache.

1. Enable mod_Proxy

  1. Enable the Apache mod_proxy module.

     $ sudo a2enmod proxy
    
  2. Enable additional modules.

     $ sudo a2enmod proxy_http
     $ sudo a2enmod proxy_balancer
     $ sudo a2enmod proxy_wstunnel
    

    Here is what each module does:

    • mod_proxy: Implements proxying on the Apache server.
    • proxy_http: Handles proxy HTTP and HTTPS requests.
    • proxy_balancer: Enables load balancing.
    • proxy_wstunnel: Tunnels web socket connections to a back-end server.
  3. Restart Apache to activate modules.

     $ sudo systemctl restart apache2
    

2. Set up the Back-end Application

As an example, set up an ownCloud container listening on port 8080 under Docker.

  1. Create the ownCloud docker container.

     $ docker run -d --name owncloud -p 8080:8080 owncloud/server
    
  2. Start ownCloud.

     $ docker start owncloud
    
  3. Verify that ownCloud is running.

     $ docker ps
    

    Output:

     CONTAINER ID   IMAGE             COMMAND                  CREATED          STATUS          PORTS                                       NAMES
     3eaea7b55cfe   owncloud/server   "/usr/bin/entrypoint…"   36 seconds ago   Up 35 seconds   0.0.0.0:8080->8080/tcp, :::8080->8080/tcp   owncloud
    

3. Setup Apache as a Reverse Proxy

  1. Back up the default Apache virtual host configuration file.

     $ sudo mv /etc/apache2/sites-available/000-default.conf  /etc/apache2/sites-available/origdefault.backup
    
  2. Create a new configuration file.

     $ sudo nano /etc/apache2/sites-available/app.example.com.conf
    
  3. Add the following contents to the file. Change app.example.com to your server name. If you are setting up a proxy for a different app than the ownCloud example, you may need to update port 8080 to your application's port number in the file below.

     <VirtualHost *:80>
    
        ServerName app.example.com
    
        ProxyPreserveHost On
        ProxyPass / http://127.0.0.1:8080/
        ProxyPassReverse / http://127.0.0.1:8080/
    
     </VirtualHost>
    
  4. Save and close the file.

    Here is what each directive means:

    • ProxyPreserveHost: Forwards the original host header to the back-end application.
    • ProxyPass: Specifies that all requests / are forwarded to the back-end application port.
    • ProxyPassReverse: Negates ProxyPass by modifying response headers from the back-end application.
  5. Activate the configuration file.

     $ sudo ln -s /etc/apache2/sites-available/app.example.com.conf  /etc/apache2/sites-enabled/app.example.com.conf
    
  6. Test the Apache configuration for errors.

     $ sudo apachectl configtest
    
  7. Restart Apache to load changes.

     $ sudo service apache2 restart
    

4. Secure the server

  1. Configure the firewall to allow HTTP traffic on port 80.

     $ sudo ufw allow 80/tcp
    
  2. Allow HTTPS on port 443.

     $ sudo ufw allow 443/tcp
    
  3. Restart the firewall.

     $ sudo ufw reload
    

5. Setup SSL

  1. Install Certbot.

     $ sudo apt install certbot python3-certbot-apache
    
  2. Request a Let's Encrypt SSL Certificate.

     $ sudo certbot -d app.example.com
    
  3. Test Auto-renewal.

     $ sudo certbot renew --dry-run
    

6. Test

Open a web browser, and visit your subdomain.

     https://app.example.com

The ownCloud login page should be displayed. Log in with the username admin, and password admin to start using the application.

More Information

You have configured Apache as a reverse proxy and set up ownCloud as the back-end application. For further information, refer to the following resources.

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