# dnsmasq

###### guide by example

![logo](https://i.imgur.com/SOa4kRd.png)

# Purpose & Overview

Lightweight DHCP and DNS server.

* [Official site](http://www.thekelleys.org.uk/dnsmasq/doc.html)
* [Arch wiki](https://wiki.archlinux.org/index.php/dnsmasq)

dnsmasq solves the problem of accessing self hosted stuff when you are inside
your network. As asking googles DNS for `blabla.org` will return your
very own public IP and most routers/firewalls wont allow this loopback,
where your requests should go out and then right back.</br>
Usual quick way to solve this issue is editing the `hosts` file on your machine,
but if more devices should "just work" it is a no-go.</br>
So the answer is running a DNS server that pairs the local machines IP with 
the correct hostnames, and a DHCP server that tells the devices on the network
to use this DNS.

# Files and directory structure

```
/etc/
├── dnsmasq.conf
├── hosts
└── resolve.conf
```              

* `dnsmasq.conf` - the main config file for dnsmasq where DNS and DHCP server is set
* `resolve.conf` - a file containing ip addresses of DNS nameservers to be used
   by the machine it resides on
* `hosts` - a file that can provide additional hostname-ip mapping

`hosts` and `resolve.conf` are just normal system files always in use on any linux
system.</br>
`dnsmasq.conf` comes with the dnsmasq installation.

# Installation

Install dnsmasq from your linux official repos.

# Configuration

Configuration file location: /etc/dnsmasq.conf

`dnsmasq.conf`

```bash
# DNS --------------------------------------------------------------------------

# Never forward plain names (without a dot or domain part)
domain-needed
# Never forward addresses in the non-routed address spaces.
bogus-priv

# If you don't want dnsmasq to read /etc/resolv.conf
no-resolv
no-poll

# DHCP and DNS interface and address
interface=enp0s25
listen-address=::1,127.0.0.1

# Upstream Google and Cloudflare nameservers
server=8.8.8.8
server=1.1.1.1

# DNS wildcards ----------------------------------------------------------------

# wildcard DNS entry sending domain and all its subdomains to an ip
address=/blabla.org/192.168.1.2
# subdomain override
address=/plex.blabla.org/192.168.1.3

# DHCP -------------------------------------------------------------------------

dhcp-authoritative
dhcp-range=192.168.1.50,192.168.1.200,255.255.255.0,480h
# gateway
dhcp-option=option:router,192.168.1.1

# DHCP static IPs --------------------------------------------------------------
# mac address : ip address

dhcp-host=08:00:27:68:f9:bf,192.168.1.150

#dhcp-leasefile=/var/lib/misc/dnsmasq.leases
```

*extra info*

* `dnsmasq --test` - validates the config
* `dnsmasq --help dhcp` - lists all the DHCP options

# resolv.conf

A file that contains DNS nameservers to be used by the linux machine,
specifically its glibc resolver library.</br>
Since dnsmasq, a DNS server, is running right on this machine,
the entries should just point to localhost.

Bit of an issue is that this file is often managed by various system services,
like dhcpcd, systemd, networkmanager... and they change it as they see fit.</br>
To prevent this, `resolv.conf` will be flagged as immutable,
which prevents all possible changes to it unless the attribute is removed.

Edit /`etc/resolv.conf` and set localhost as the DNS nameserver.

`resolv.conf`
```
nameserver ::1
nameserver 127.0.0.1
```

Make it immutable to prevent any changes to it.

* `chattr +i /etc/resolv.conf`

Check if the content is what was set.

* `cat /etc/resolv.conf`

If it was changed by dhcpcd before the +i flag took effect, edit `/etc/dhcpcd.conf`
and add `nohook resolv.conf` at the end.</br>
Restart the machine, disable the immutability, edit it again,
add immutability, and check.

* `sudo chattr -i /etc/resolv.conf`
* `sudo nano /etc/resolv.conf`
* `sudo chattr +i /etc/resolv.conf`
* `cat /etc/resolv.conf`

# /etc/hosts

This is a file present on every system, linux, windows, mac, android,... 
where you can assign a hostname to an IP.</br>
dnsmasq reads `/etc/hosts` for IP hostname pairs and adds them to its own
resolve records.

Unfortunately no wildcard support.
But as seen in the `dnsmasq.conf` there is a wildcard section solving this,
so blabla stuff here is just for show. 

`hosts`
```
127.0.0.1       docker-host
192.168.1.2     docker-host 
192.168.1.1     gateway
192.168.1.2     blabla.org
192.168.1.2     nextcloud.blabla.org
192.168.1.2     book.blabla.org
192.168.1.2     passwd.blabla.org
192.168.1.2     grafana.blabla.org
```

# Start the service

`sudo systemctl enable --now dnsmasq`

*Make sure you disable other DHCP servers on the network,
usually a router is running one.*

# Test it

#### DHCP

Set some machine on the network to use DHCP for its network setting.</br>
It should just work. 

You can check on the dnsmasq host, file `/var/lib/misc/dnsmasq.leases`
for the active leases. Location of the file can vary base on your linux distro.

#### DNS

nslookup is utility that checks DNS mapping, part of `bind-utils` or `bind-tools`,
again depending on the distro.

* `nslookup google.com`
* `nslookup gateway`
* `nslookup docker-host`
* `nslookup blabla.org`
* `nslookup whateverandom.blabla.org`
* `nslookup plex.blabla.org`

# Update

During host linux packages update.

# Backup and restore

#### Backup

Using [BorgBackup setup](https://github.com/DoTheEvo/selfhosted-apps-docker/tree/master/borg_backup)
that makes daily snapshot of the entire /etc directory
which contains the config files.

#### restore

Replace the content of the config files with the one from the backup.