How To: Modify DNS¶

This document will go over what DNS and Domains are, and how to add a subdomain to cspp.ie and host something on it!

DNS, or Domain Name System is a system which converts IP Addresses to the URLs that we all know and love, for example:

Bash

nslookup
Default Server: UnKnown
Address: 1.1.1.1

> google.com
Name:    google.com
Addresses:  2a00:1450:4009:826::200e
          142.250.200.14

In this case, the IP Address for google.com is 142.250.200.14.

A Short(ish) Introduction to DNS and Domains¶

CS++ currently owns the cspp.ie domain. This domain is broken down in two parts:

TOP LEVEL DOMAIN: .ie, this is the two-letter code for Irish Websites.

DOMAIN NAME: cspp, this is our unique domain name.

You can add a thing called 'subdomains' to a domain, for example, this website is docs.cspp.ie, which is a Subdomain.

What Do We Use Domains and DNS For?¶

We use it to make it easy to access our services, such as our website, documentation, password manager, etc.

The cspp.ie domain identifies everything using it as ours.

We also sometimes use subdomains to make the lives of our members easier! The Discord server can be accessed at discord.cspp.ie ⧉, and so on!

Where is All of This Stored?¶

The cspp.ie domain is bought from Smarthost ⧉ and paid for annually. As of right now, it is in the name of Ruán Murgatroyd.

We control our DNS records on Contabo ⧉.

Adding a Subdomain¶

BE REALLY CAREFUL!!!

Changes to DNS can be potentially catastrophic to the society, and can cause long downtimes!

Make sure you know exactly what you're doing, and don't touch anything you're not actively working on!

If possible, get a second set of eyes to go over everything you're doing!!!!

First, navigate to Contabo ⧉ and log in with the CS++ account.

Then navigate to DNS Zone Management and click the NOTEBOOK AND PENCIL icon beside cspp.ie

Here you will see a list of all of our DNS info for cspp.ie, so let's add one!

Adding a DNS Record¶

In the form at the bottom, add the subdomain you'd like, let's use test as an example.

Keep the rest of the form the same, and set the Data field to the IP Address you wish to point the domain at. Let's use Huey Dewey Louie as an example, enter 158.220.114.253 in the data field.

What Do These Fields Mean?

name: The subdomain name

TTL: Time-To-Live - How long the record will be stored by devices before they go and ask again for the data.

Type: The type of record, this can be subdomains, mail records, text records, etc.

Priority: The priority for mail records.

Data: The IP address / text record, etc.

Once you have filled out all the data, click create record.

You have now created your first record, congrats! But right now, it's doing nothing. Going to test.cspp.ie will not show anything, or show a random service we are running.

Running a Service on the Subdomain¶

Now that we have a subdomain, we need to have something that we want to serve to people on it.

For this example, we will run a basic NGINX container.

SSH into the server you pointed the subdomain at (If you do not know how to SSH, read this).

Now, run the following command:

Bash

docker run -d -p [PORT]:80 -p [PORT_2]:443 --name SUBDOMAIN nginx

This will create an NGINX container (NGINX is a webserver). Replace [PORT] and [PORT_2] with port numbers, make sure these port numbers are not in use elsewhere on the system!

This will then create an NGINX container, running on PORT and PORT_2. We now need to point the subdomain at these ports. This is called a 'Reverse Proxy'.

Setting up a Reverse Proxy¶

To set up the reverse proxy, run the following command:

Bash

cs /etc/nginx/sites-available
sudo cp rp_template [SUBDOMAIN].cspp.ie

You may be prompted to enter your user password.

Then open this file in a text editor like nano or vim.

It will look like this:

Nginx Configuration File

server {
    server_name SUBDOMAIN.cspp.ie;

    location / {
        proxy_pass http://localhost:PORT;
        include proxy_params;
    }

    listen 80;
}

Replace SUBDOMAIN and PORT with the subdomain and PORT configured earlier, then save and exit the file.

Make sure the server_name matches the name of the file!

Now we need to enable this site.

Enabling the Site¶

We use sites-available and sites-enabled in NGINX for our domain configs.

sites-available:

This stores the config files for each domain we serve.

sites-enabled:

This allows the domain to be served.

To do this, run the following command:

Bash

sudo ln -s /etc/nginx/sites-available/[SUBDOMAIN].cspp.ie /etc/nginx/sites-enabled/

Make sure to use the FULL paths, instead of short-hand.

Now, make sure the config works correctly with:

Bash

sudo nginx -t

If the config is correct, it will return:

Text Only

nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

Then reload NGINX with:

Bash

sudo systemctl reload nginx

You can now navigate to the site, but it will warn about no certificate! We need to enable HTTPS!

Enabling HTTPS¶

We use certbot from Let's Encrypt ⧉ for free TLS (that means HTTPS) certificates!

Run the following:

Bash

sudo certbot --nginx

Which will output something like the following:

Text Only

Saving debug log to /var/log/letsencrypt/letsencrypt.log

Which names would you like to activate HTTPS for?
We recommend selecting either all domains, or all domains in a VirtualHost/server block.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
1: cspp.ie
2: discord.cspp.ie
3: www.cspp.ie
4: [SUBDOMAIN].cspp.ie
...
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Select the appropriate numbers separated by commas and/or spaces, or leave input
blank to select all options shown (Enter 'c' to cancel):

You will want to generate a certificate for [SUBDOMAIN].cspp.ie, so type the number its number in (in this case 4), and press enter.

Assuming everything goes correctly, the following should display:

This may take a while to actually run, please be patient!

Text Only

Requesting a certificate for [SUDBDOMAIN].cspp.ie

Successfully received certificate.
Certificate is saved at: /etc/letsencrypt/live/[SUBDOMAIN].cspp.ie/fullchain.pem
Key is saved at:         /etc/letsencrypt/live/[SUBDOMAIN].cspp.ie/privkey.pem
This certificate expires on 2024-10-04.
These files will be updated when the certificate renews.
Certbot has set up a scheduled task to automatically renew this certificate in the background.

Deploying certificate
Successfully deployed certificate for [SUBDOMAIN].cspp.ie to /etc/nginx/sites-enabled/[SUBDOMAIN].cspp.ie
Congratulations! You have successfully enabled HTTPS on https://[SUBDOMAIN].cspp.ie

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
If you like Certbot, please consider supporting our work by:
 * Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
 * Donating to EFF:                    https://eff.org/donate-le
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

This TLS cert will automatically renew, so no need to worry!

Navigate to your subdomain and see the 'Welcome to nginx!' page.

Congratulations! You have successfully created your first subdomain!

Happy domaining!