DNS

DNS#

Domain Name System (DNS) is how human-readable domains, like book.the-turing-way.org get translated to Internet Protocol (IP) addresses that computers use to locate each other. You can think of DNS like a phone book for the internet. Without it, you wouldn’t be able to use domain names to find websites or services. DNS is configured by creating records, which give instructions on how to handle requests depending on the domain name.

On the internet, DNS is managed by a series of connect providers. Google has a DNS service at 8.8.8.8 and 8.8.4.4. Cloudflare has a DNS service at 1.1.1.1. DNS servers are connected and propagate records to each other. That means, if you want to host something on your domain you don’t have to create records on every DNS server for the public to find it.

It is very likely that you will use a DNS server run by your internet provider, although you can often change this. DNS is not encrypted, so in theory the DNS server you use can see what domains you are requesting. However, DNS over HTTPS is available and becoming more common.

To learn more about DNS you can read Cloudflare’s DNS learning documents.

Summary of Records#

There are many DNS record types. The following table gives a simple explanation of some of the more common ones.

Record

Purpose

A

Directs a hostname to an IPv4 address

AAAA

The same as A but for IPv6

CNAME

Makes the hostname an alias for another

MX

Points to an email server for the domain

TXT

Arbitrary text, often used to configure SSL or email authentication

NS

Delegates DNS to a different nameserver

Looking at DNS Records#

You can inspect DNS records using the dig or nslookup commands.

The dig command line can be formatted like

dig [@DNS-server] [domain] [record-type]

For example, we can check the CNAME record for book.the-turing-way.org using Google’s DNS server (8.8.8.8) like this

$ dig @8.8.8.8 book.the-turing-way.org CNAME

; <<>> DiG 9.10.6 <<>> @8.8.8.8 book.the-turing-way.org CNAME
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 64376
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;book.the-turing-way.org.       IN      CNAME

;; ANSWER SECTION:
book.the-turing-way.org. 1800   IN      CNAME   book.the-turing-way.org.

;; Query time: 75 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Mon Mar 18 14:47:29 GMT 2024
;; MSG SIZE  rcvd: 92

We can see in the answer section that there is a CNAME record meaning that book.the-turing-way.org is an alias for book.the-turing-way.org. What happens if you look for a TXT record at egg.the-turing-way.org?

The Turing Way Records#

The Turing Way’s DNS records are managed on NameCheap by the DNS team, a sub-team of the Infrastructure Working Group. Here we describe the records that have been created for The Turing Way.

The records are in the format,

domain type value

The domain @ means the root domain, like example.com. Otherwise the domain is a subdomain of the root domain. For example www would mean www.example.com

CNAME records#

As explained in Summary of Records CNAME records are aliases. We use a CNAME record for The Turing Way book at book.the-turing-way.org. This is an alias for the domain where the book is hosted, which is currently on Netlify. If the book is moved to another hosting provider the record can be updated to point to the new host. That way, the book will always be accessible at book.the-turing-way.org no matter how or where it is hosted.

book CNAME book.the-turing-way.org.

URL Redirects#

Namecheap DNS allows redirecting to URLs. This is not actually part of DNS and is achieved by returning HTTP redirect signals to requests (like 301 or 302). You could do the same by having your webserver redirect requests to particular subdomains. For example, in NGINX you could use rewrite.

The following URL redirects are configured,

Directing the root domain (the-turing-way.org) to the start page

@ URL-Redirect https://the-turing-way.start.page

Directing git.the-turing-way.org to the GitHub organisation

git URL-Redirect https://github.com/the-turing-way

Directing slack.the-turing-way.org to the Slack invitation link

slack URL-Redirect <slack invite link>

Directing news.the-turing-way.org to the newsletter archive

news URL-Redirect https://buttondown.email/turingway
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