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214 lines
6.0 KiB
Markdown
214 lines
6.0 KiB
Markdown
# dnsmasq
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###### guide by example
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# Purpose & Overview
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Lightweight DHCP and DNS server.
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* [Official site](http://www.thekelleys.org.uk/dnsmasq/doc.html)
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* [Arch wiki](https://wiki.archlinux.org/index.php/dnsmasq)
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dnsmasq solves the problem of accessing self hosted stuff when you are inside
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your network. As asking googles DNS for `blabla.org` will return your
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very own public IP and most routers/firewalls wont allow this loopback,
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where your requests should go out and then right back.</br>
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Usual quick way to solve this issue is editing the `hosts` file on your machine,
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but if more devices should "just work" it is a no-go.</br>
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So the answer is running a DNS server that pairs the local machines IP with
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the correct hostnames, and a DHCP server that tells the devices on the network
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to use this DNS.
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# Prerequisites
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* machine that will be running it should have set static IP
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# Files and directory structure
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```
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/etc/
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├── dnsmasq.conf
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├── hosts
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└── resolve.conf
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```
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* `dnsmasq.conf` - the main config file for dnsmasq where DNS and DHCP functionality is set
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* `resolve.conf` - a file containing ip addresses of DNS nameservers to be used
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by the machine it resides on
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* `hosts` - a file that can provide additional hostname-ip mapping
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`hosts` and `resolve.conf` are just normal system files always in use on any linux
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system.</br>
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`dnsmasq.conf` comes with the dnsmasq installation.
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# Installation
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Install dnsmasq from your linux official repos.
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# Configuration
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`dnsmasq.conf`
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```bash
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# DNS --------------------------------------------------------------------------
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# Never forward plain names (without a dot or domain part)
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domain-needed
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# Never forward addresses in the non-routed address spaces.
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bogus-priv
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# If you don't want dnsmasq to read /etc/resolv.conf
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no-resolv
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no-poll
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cache-size=1000
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# interface and address
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interface=enp0s25
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listen-address=::1,127.0.0.1
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# Upstream Google and Cloudflare nameservers
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server=8.8.8.8
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server=1.1.1.1
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# DNS wildcards ----------------------------------------------------------------
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# wildcard DNS entry sending domain and all its subdomains to an ip
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address=/blabla.org/192.168.1.2
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# subdomain override
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address=/plex.blabla.org/192.168.1.3
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# DHCP -------------------------------------------------------------------------
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dhcp-authoritative
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dhcp-range=192.168.1.50,192.168.1.200,255.255.255.0,480h
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# gateway
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dhcp-option=option:router,192.168.1.1
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# DHCP static IPs --------------------------------------------------------------
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# mac address : ip address
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dhcp-host=08:00:27:68:f9:bf,192.168.1.150
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#dhcp-leasefile=/var/lib/misc/dnsmasq.leases
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```
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*extra info*
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* `dnsmasq --test` - validates the config
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* `dnsmasq --help dhcp` - lists all the DHCP options
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You can also run **just DNS server**, by deleting the DHCP section
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in the `dnsmasq.conf` to the end.</br>
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Then on your router, in the DHCP>DNS settings, you just put in the ip address
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of the dnsmasq host as the DNS server.
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# resolv.conf
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`resolv.conf`
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```
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nameserver ::1
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nameserver 127.0.0.1
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```
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A file that contains DNS nameservers to be used by the linux machine it sits on.</br>
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Since dnsmasq, a DNS server, is running right on this machine,
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the entries just point to localhost:</br>
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`nameserver ::1`</br>
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`nameserver 127.0.0.1`
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Bit of an issue is that this file is often managed by various system services,
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like dhcpcd, systemd, networkmanager... and they change it as they see fit.</br>
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To prevent this, `resolv.conf` will be flagged as immutable,
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which prevents all possible changes to it unless the attribute is removed.
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Edit /`etc/resolv.conf` and set localhost as the DNS nameserver, as shown above.
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Make it immutable to prevent any changes to it.
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* `chattr +i /etc/resolv.conf`
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Check if the content is what was set.
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* `cat /etc/resolv.conf`
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If it was changed by dhcpcd before the +i flag took effect, edit `/etc/dhcpcd.conf`
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and add `nohook resolv.conf` at the end.</br>
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Restart the machine, disable the immutability, edit it again,
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add immutability, and check.
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* `sudo chattr -i /etc/resolv.conf`
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* `sudo nano /etc/resolv.conf`
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* `sudo chattr +i /etc/resolv.conf`
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* `cat /etc/resolv.conf`
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# /etc/hosts
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`hosts`
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```
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127.0.0.1 docker-host
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192.168.1.2 docker-host
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192.168.1.1 gateway
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192.168.1.2 blabla.org
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192.168.1.2 nextcloud.blabla.org
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192.168.1.2 book.blabla.org
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192.168.1.2 passwd.blabla.org
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192.168.1.2 grafana.blabla.org
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```
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This is a file present on every system, linux, windows, mac, android,...
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where you can assign a hostname to an IP.</br>
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dnsmasq reads `/etc/hosts` for IP hostname pairs and adds them to its own
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resolve records.
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Unfortunately no wildcard support.
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But as seen in the `dnsmasq.conf` there is a wildcard section solving this,
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so `blabla.org` stuff here is just for show.
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# Start the service
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`sudo systemctl enable --now dnsmasq`
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*Make sure you disable other DHCP servers on the network,
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usually a router is running one.*
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# Test it
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#### DHCP
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Set some machine on the network to use DHCP for its network setting.</br>
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It should just work.
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You can check on the dnsmasq host, file `/var/lib/misc/dnsmasq.leases`
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for the active leases. Location of the file can vary base on your linux distro.
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#### DNS
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nslookup is utility that checks DNS mapping,
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part of `bind-utils` or `bind-tools` packages, again depending on the distro.
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* `nslookup google.com`
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* `nslookup gateway`
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* `nslookup docker-host`
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* `nslookup blabla.org`
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* `nslookup whateverandom.blabla.org`
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* `nslookup plex.blabla.org`
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# Update
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During host linux packages update.
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# Backup and restore
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#### Backup
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Using [borg](https://github.com/DoTheEvo/selfhosted-apps-docker/tree/master/borg_backup)
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that makes daily snapshot of the /etc directory which contains the config files.
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#### restore
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Replace the content of the config files with the one from the backup.
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