nsd-dyndns is a simple script that adds dynamic DNS dunctionality to NSD (authoritative DNS name server).
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
Add the following new virtual host to your /etc/httpd.conf:
server "update.example.com" {
listen on $ext_addr port 80
root "/htdocs/dyndns"
log access dyndns.log
}
Add the following to your nginx.conf. The "access" log format isn't avaliable by default so you have to define it.
http {
...
log_format access '$host $remote_addr - $remote_user [$time_local] '
'"$request" $status $body_bytes_sent '
'"$http_referer" "$http_user_agent" "$gzip_ratio"';
...
server {
listen 80;
server_name update.example.com;
root /htdocs/dyndns;
access_log /var/www/logs/dyndns.log access;
...
}
}
Create an empty update.html:
# mkdir /var/www/htdocs/dyndns/
# touch /var/www/htdocs/dyndns/update.html
After reloading webserver, try to access http://update.example.com/update.html The request should show up in /var/www/logs/dyndns.log
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 ns2.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
- 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 to query the following URL:
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.
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