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slide: added a slide on DNS

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silver 2023-10-14 17:13:43 +01:00
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title = "Skynet: DNS"
date = 2023-10-14
slides = true
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# DNS
-------------------------------------------------------------------------
## Overview
-------------------------------------------------------------------------
DNS is both simple and complex.
-------------------------------------------------------------------------
DNS translates the human domains into something computers can understand.
-------------------------------------------------------------------------
```dns
skynet IN A 193.1.96.165
*.users IN CNAME skynet
```
-------------------------------------------------------------------------
It can also provide useful information.
-------------------------------------------------------------------------
```dns
skynet.ie. IN TXT "v=spf1 a:mail.skynet.ie -all"
```
-------------------------------------------------------------------------
## Structure
-------------------------------------------------------------------------
DNS is hierarchical and delegated.
-------------------------------------------------------------------------
Root servers
-------------------------------------------------------------------------
TLD (Top Level Domain) servers (``.ie``, ``.com``, ``.eu``)
-------------------------------------------------------------------------
Domain servers (``skynet.ie``)
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We run our own DNS servers, Bind9 (``ns1.skynet.ie``, ``ns2.skynet.ie``)
-------------------------------------------------------------------------
We also have control over ``csn.ul.ie`` and ``ulcompsoc.ie``
-------------------------------------------------------------------------
## Viewing DNS records
-------------------------------------------------------------------------
On the nixos repo:
```bash
colmena build --keep-result --on vendetta
cat .gcroots/node-vendetta/etc/skynet/dns/skynet.ie
```
-------------------------------------------------------------------------
On top of that we also manage the reverse DNS (rDNS)
-------------------------------------------------------------------------
Reverse DNS allows you to look up and IP and get the domains.
-------------------------------------------------------------------------
```bash
cat .gcroots/node-vendetta/etc/skynet/dns/64-64.99.1.193.in-addr.arpa
```
-------------------------------------------------------------------------
To validate them there is this tool: <<https://bind.jamiewood.io/>>
(put ``skynet.ie`` in teh FQDN box)
-------------------------------------------------------------------------
## Commands
-------------------------------------------------------------------------
```bash
dig skynet.ie
dig skynet.ie @1.1.1.1
dig skynet.ie @ns1.skynet.ie
host 193.1.99.75
```
-------------------------------------------------------------------------
//Use this time to explore the nixos repo to explain//
-------------------------------------------------------------------------
* <<https://gitlab.skynet.ie/compsoc1/skynet/nixos/-/issues/21>>
* <<https://gitlab.skynet.ie/compsoc1/skynet/nixos/-/issues/33>>