Configuring the NGINX Server - HTTP Virtual Hosts / Rewrites / Custom Error Pages / Directives

We're going to become the 'root' user.

sudo su -

First, change to the /etc/nginx/sites-available directory so we can add the new virtual host configuration block:

cd /etc/nginx/sites-available

We're going to copy the configuration file related to the virtual host for site3.bigstatecollege.edu:

cp site3.bigstatecollege.edu.conf site4.bigstatecollege.edu.conf

Edit the configuration file for site4:

vi site4.bigstatecollege.edu.conf

Change the port that the virtual host is listening on to 8081:

listen 8081;

Also, change the site3 entries for the root directory and the server_name to point to site4. Save and exit the new configuration file for site4.bigstatecollege.edu.

Create a soft link in /etc/nginx/sites-enabled to "activate" the configuration:

ln -s /etc/nginx/sites-available/site4.bigstatecollege.edu.conf /etc/nginx/sites-enabled/site4.bigstatecollege.edu.conf 

Validate and restart NGINX:

nginx -t
systemctl reload nginx

Test the virtual host:

curl http://site4.bigstatecollege.edu:8081

We should see the following:

Welcome to site4.bigstatecollege.edu!

There's a download directory for legacy website downloads, and a virtual host (port 8084). We wish to present this directory as http://www.bigstatecollege.edu/downloads/.

ls -la /var/www/download_files

We can get to the file via http://downloads.bigstatecollege.edu:8084/file1:

curl http://downloads.bigstatecollege.edu:8084/file1.txt

Edit the configuration file:

vi bigstatecollege.edu.conf

Add the following section:

        location /downloads {
                rewrite ^(/downloads)/(.*)$ http://downloads.bigstatecollege.edu:8084/$2 permanent;
                return 403;
        }

This will pass the file name in the /downloads part of the URL to the new URL as the second argument ($2).

Validate and restart NGINX:

nginx -t
systemctl reload nginx

Test the rewrite:

curl http://www.bigstatecollege.edu/downloads/file1.txt

Retry the request with the new location:

curl -L http://www.bigstatecollege.edu/downloads/file1.txt

To see what's going on behind the scenes, use the '-I' switch with curl:

curl -I http://www.bigstatecollege.edu/downloads/file1.txt

The Location information points to http://downloads.bigstatecollege.edu:8084/file1.txt.

We've provided a custom 404 error page on the lab server that is branded for bigstatecollege.edu. This file is /var/www/html/BSC_404.html.

cat /var/www/html/BSC_404.html

Try accessing a file that doesn't exist with curl:

curl http://www.bigstatecollege.edu/nofile.txt

We will get a generic error page.

We will need to configure our custom error page in the bigstatecollege.edu virtual host server configuration file:

vi bigstatecollege.edu.conf

We're going to add a section of code to configure a custom error page for 404 errors:

        error_page 404 /BSC_404.html;
        location = /BSC_404.html {
                root /var/www/html;
                internal;
        }

Save and exit the configuration file.

Test the NGINX configuration and reload the NGINX service:

nginx -t
systemctl reload nginx

Now, try accessing the file that doesn't exist:

curl http://www.bigstatecollege.edu/nofile.txt

We now see the custom error page.

Big State College is building an application backend, which they want to proxy under http://www.bigstatecollege.edu/app. The backend application servers are already up and running. We can validate this using curl:

curl http://app1.bigstatecollege.edu:8085
curl http://app2.bigstatecollege.edu:8086
curl http://app3.bigstatecollege.edu:8087

Define a group of (application) servers using the upstream directive:

vi bigstatecollege.edu.conf

Add the following at the beginning of the configuration file:

upstream bscapp  {
   server app1.bigstatecollege.edu:8085;
   server app2.bigstatecollege.edu:8086 backup;
   server app3.bigstatecollege.edu:8087 backup;
}

Add a location block for the app directory:

        location /app {
                proxy_pass http://bscapp/;
        }

Save and exit the file.

Validate and reload NGINX:

nginx -t
systemctl reload nginx

Test the upstream:

curl http://www.bigstatecollege.edu/app

We will see that the app1.bigstatecollege.edu server is serving requests. The other two servers are backups right now.

Mark the app1 server as down in the upstream configuration, and see if the backup servers take over:

upstream bscapp  {
   server app1.bigstatecollege.edu:8085 down;
   server app2.bigstatecollege.edu:8086 backup;
   server app3.bigstatecollege.edu:8087 backup;
}

Validate and reload NGINX. Test the upstream:

curl http://www.bigstatecollege.edu/app

We will see that NGINX pulls from both the app2 and app3 servers.

Edit the configuration file and remove the down from app1 in the bscapp group:

upstream bscapp  {
   server app1.bigstatecollege.edu:8085;
   server app2.bigstatecollege.edu:8086 backup;
   server app3.bigstatecollege.edu:8087 backup;
}

Save, exit, validate and restart the NGINX service. Test the upstream:

curl http://www.bigstatecollege.edu/app

We should get Welcome to app1.bigstatecollege.edu!. The app2 and app3 servers are only acting as backups.