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108 lines
3.6 KiB
Markdown
108 lines
3.6 KiB
Markdown
---
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title: Dynamic DNS for NSD
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type: post
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author: micha
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date: 2018-05-03T02:26:11+00:00
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url: /dynamic-dns-for-nsd/
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tags:
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- DNS
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- OpenBSD
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- Linux
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- Software
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---
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# Introduction
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nsd-dyndns is a simple script that adds dynamic DNS dunctionality to NSD (authoritative DNS name server).
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# Requirements
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The following is required or suggested:
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* OpenBSD (or another BSD or some Linux distro) with HTTPD and NSD installed (pkg_add nsd), configured and running
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* (sub-)domain for your webserver. Needed for updating the NS record of your actual DynDNS domain.
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* In this example: _update.example.com_
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* (sub-)domain that is updated dynamically.
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* In this example: _dyn.example.com_
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* A router capable of sending custom GET-requests to your DynDNS server.
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* In this example: A FritzBox
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# Installation
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## Configure your HTTPD
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Add the following new virtual host to your _/etc/httpd.conf_:
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server "update.example.com" {
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listen on $ext_addr port 80
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root "/htdocs/dyndns"
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log access dyndns.log
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}
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Create an empty _update.html_:
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# mkdir /var/www/htdocs/dyndns/
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# touch /var/www/htdocs/dyndns/update.html
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After reloading HTTPD, try to access [http://update.example.com/update.html] The request should show up in _/var/www/logs/dyndns.log_
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## **Create a zone file for dyn.example.com**
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Create a new zone file (e.g. at _/var/nsd/zones/dyn.example.com.zone_) with the following content
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$ORIGIN example.com.
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$TTL 300
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@ IN SOA ns1.example.com. admin.example.com. (
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1524952218
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300 ; refresh
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900 ; retry
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1209600 ; expire
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1800 ; ttl
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)
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; Name servers
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IN NS ns1.example.com.
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IN NS ns1.example.com.
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; A records
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@ IN A 123.123.123.123
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update IN A 123.123.123.123
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dyn IN A 123.123.123.123
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Don't forget to set your own domain names, name servers and ip addresses Furthermore, add this zone file to your _/var/nsd/etc/nsd.conf_
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## Configure and Install nsd-dyndns
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* Download the scripts from here: [https://git.qrz.is/clemens/nsd-dyndns](https://git.qrz.is/clemens/nsd-dyndns)
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* Copy _dyndns.conf-dist_ to _/etc/dyndns.conf_
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* _\# cp dyndns.conf-dist /etc/dyndns.conf_
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* Edit _/etc/dyndns.conf_ to your needs
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* Copy _dyndns.sh_ to _/usr/local/bin/dyndns.sh_
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* _\# cp dyndns.sh /usr/local/bin/dyndns.sh_
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* Make the script executable:
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* _\# chmod u+x /usr/local/bin/dyndns.sh_
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* Add _/usr/local/bin/dyndns.sh_ to your crontab
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## Configure your router
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Configure your router to query the following URL:
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http://update.example.com/update.html?qwertzuiop1234567890
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Don't forgert to set your own domain name and to replace the string after "?" with the password you configured in the config file.
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# What it does
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When your router gets a new IP and therefore sends an HTTP request to your server, a similar entry should appear in your _/var/www/logs/dyndns.log_:
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update.example.com 123.123.123.123 - - [29/Apr/2018:20:48:19 +0200] "GET /update.html?qwertzuiop1234567890 HTTP/1.1" 200 6
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When the script is executed e.g. via cron, the following happens:
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* It greps the last line of _/var/www/logs/dyndns.log_ where the correct password was found and extracts the requesting IP address
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* It checks if this IP is the same than the last time
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* If it's a new IP, then it replaces the forth line in your zone file (the line with the version number) with a new version (current unix time stamp)
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* As a second step, it updates the A record of you DynDNS domain (dyn.example.com in our example)
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* It then stores the new IP in the file _/tmp/last\_dyndns\_ip.txt_
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* Finally it reloads NSD
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