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