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DNS Basics for Websites and Email Servers

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This article aims to explain what various DNS records are and how to use them. It is aimed at people hosting websites and email servers on a home server such as a raspberry pi.

How DNS Works

DNS stands for Domain Name System. In a nutshell, it's the system that we use to translate human readable domain names (e.g. samhobbs.co.uk) into the Internet Protocol (IP) addresses for those services (e.g. 195.166.151.235).

The DNS system has a strict hierarchy, and lookups are performed recursively using a client/server model. This means that when your computer asks for the IP address for "subdomain.example.com", the DNS resolver you are using starts at the top and works backwards to find the address. The servers at the top of the pyramid (root name servers) direct clients to the name servers reponsibe for Top Level Domains (TLD, e.g. .com), and that server in turn is able to tell the client which name server is authoritative for the second level domain (e.g. example.com), and so on. Usually for small sites, the DNS records for your domain are managed by your Domain Name Registrar.

The DNS resolver doesn't have to perform all these lookups every time, because each record has a Time To Live (TTL) in seconds, which tells the client how long they can cache the information for until it should be refreshed. That's Time To Live (live free), not Live (live electrical circuit), which is how I first read it!

There are loads of different types of DNS record, so I've picked the most important ones you might need or want to use. These are:

  1. DNS A - used to map a host name to an IP address
  2. Mail Exchanger (MX) - used to tell clients which hostnames are used for email services
  3. Sender Policy Framework (SPF) - used to define which servers are allowed to send email from your domain name
  4. Pointer (PTR) - the opposite of DNS A, this record maps an IP address to the hostname

For a website, you only need a DNS A record. For an email server, you need at least a DNS A record and an MX record; PTR and SPF records will help you get your email through spam filters.

I'll be illustrating how to set up the different types of record using Namecheap, my Domain Name Registrar, as an example. If you haven't registered a domain name yet, I'd recommend Namecheap -avoid GoDaddy if you can, since they have some pretty horrible pricing practices and consistently back the wrong side when it comes to internet censorship acts like SOPA and PIPA.

How to Install WordPress on a Raspberry Pi

WordPress on Raspberry Pi

This tutorial will show you how to take a vanilla Raspbian image and turn it into a HTTP server hosting one or more WordPress website.

I’ve previously written a few bits and pieces about WordPress, but I’ve never actually covered how to install it on a Raspberry Pi until now.

This was one of the first things I did with my Pi, so I’m going to assume you know very little and try to be as detailed as possible.

The actual WordPress bit is very quick and easy once the ground work is done: wordpress.org has a 5 minute installation guide, but it doesn’t tell you how to do the difficult bits! This tutorial will cover everything you need, from the ground up.

Webalizer: a Free, Open Source Alternative to Google Analytics for Raspberry Pi

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Google Analytics is everywhere. Seriously, everywhere. So much so that Google probably has a complete record of you hopping from site to site during your normal browsing, information that happens to be both extremely valuable to them and a pretty serious invasion of your privacy.

Multiple Websites and Subdomains with SSL/TLS in Apache2: Virtualhosts

Want to host more than one website on your Raspberry Pi, without having to pay for multiple IP addresses? You can do this easily using Apache’s name-based VirtualHost configuration feature.

This feature allows someone to connect to your Raspberry Pi (or other server) and get served different content based on the host header they sent with their request. This is automatic, and the user is none the wiser: they simply type your web address in the header, and your server uses that information to decide which website to display. Unless you tell them, they won’t know the Pi is also hosting other content.

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