Bind9 installation

apt install bind9

vim /etc/bind/named.conf

zone "dyndns.example.com" {
  type master;
  file "/var/cache/bind/dyndns.example.com.db";
  allow-update { key "dyndns.example.com."; };
};

tsig-keygen -a hmac-sha512 dyndns.example.com

vim /etc/bind/named.conf.local

key "dyndns.example.com." {
  algorithm hmac-sha512;
  secret "nbB5i/5pyFywRPaUpEkzxtS0she1JOuZlASceu0lLU8Pe7dYpzuVDn9vbGvof2wjGkVsSZBG2DlaM3RwPHkd9g==";
};

vim /var/cache/bind/dyndns.example.com.db

$ORIGIN dyndns.example.com.
$TTL 300 ; 5 minutes

;; NAME IN SOA MNAME RNAME
; NAME: name of the zone
; IN: zone class (usually IN for internet)
; SOA: abbreviation for Start of Authority
; MNAME: Primary master name server for this zone
; RNAME: Email address of the administrator responsible for this zone. address is encoded as a name. (john\.doe.example.com.)

@   IN SOA  ns1.example.com. admin.example.com. (
    1  ; SERIAL: Serial number for this zone.
    3600       ; REFRESH: number of seconds after which secondary name servers should query
    1000       ; RETRY: number of seconds after which secondary name servers should retry to request
    3600000    ; EXPIRE: number of seconds after which secondary name servers should stop answering request
    300        ; TTL: Time To Live for purposes of negative caching
    )
      NS    ns1.example.com.
      NS    ns2.example.com.
      A     185.11.138.33
      AAAA  2a03:2900:7:96::2

systemctl enable named.service

systemctl start named.service

Test Bind9 setup

echo "server ns1.example.com
debug
update add debug.dyndns.example.com. 10 IN TXT \"$(date)\"
send
quit
" | nsupdate -y 'hmac-sha512:dyndns.example.com:nbB5i/5pyFywRPaUpEkzxtS0she1JOuZlASceu0lLU8Pe7dYpzuVDn9vbGvof2wjGkVsSZBG2DlaM3RwPHkd9g=='

Show all records of the zone dyndns.example.com

dig @ns1.example.com. dyndns.example.com. axfr (axfr = Asynchronous Xfer Full Range)

dyndns installation

Install dyndns into the directory /usr/local/share/python-virtualenv/dyndns using a virtual environment.

python3 -m venv /usr/local/share/python-virtualenv/dyndns
source /usr/local/share/python-virtualenv/dyndns/bin/activate
pip3 install dyndns

The working directory of our flask web API is in the directory /var/www/dyndns.example.com. Create a file /var/www/dyndns.example.com/dyndns.ini.

[uwsgi]
module = dyndns.wsgi:app

master = true
processes = 5

socket = /var/www/dyndns.example.com/dyndns.sock
chmod-socket = 664
uid = www-data
gid = www-data
vacuum = true

die-on-term = true

Example configuration file for nginx: /etc/nginx/sites-available/dyndns.example.com.

server {
  server_name dyndns.example.com;
  listen 80;
  listen [::]:80;
  return 301 https://$host$request_uri;
}

server {
  listen 443 ssl;
  listen [::]:443 ssl;
  server_name dyndns.example.com;
  ssl_certificate /etc/letsencrypt/live/dyndns.example.com/fullchain.pem;
  ssl_certificate_key /etc/letsencrypt/live/dyndns.example.com/privkey.pem;

  location / {
    include uwsgi_params;
    uwsgi_pass unix:/var/www/dyndns.example.com/dyndns.sock;
  }

}

vim /etc/systemd/system/dyndns.service

[Unit]
Description=uWSGI instance to serve dyndns
After=network.target

[Service]
User=www-data
Group=www-data
WorkingDirectory=/var/www/dyndns.example.com
Environment="PATH=/usr/local/share/python-virtualenv/dyndns/bin"
ExecStart=/usr/local/share/python-virtualenv/dyndns/bin/uwsgi --ini uwsgi.ini

[Install]
WantedBy=multi-user.target

systemctl enable dyndns.service

systemctl start dyndns.service

Update by path

1. <your-domain>/update-by-path/secret/fqdn

2. <your-domain>/update-by-path/secret/fqdn/ip_1

3. <your-domain>/update-by-path/secret/fqdn/ip_1/ip_2

Update by query

<your-domain>/update-by-query?secret=secret&fqdn=fqdn&ip_1=1.2.3.4

Delete by path

Hit this url to delete a DNS record corresponding to the fqdn. Both ipv4 and ipv6 entries are deleted.

<your-domain>/delete-by-path/secret/fqdn

Update script

To update the dyndns server you can use the corresponding shell script dyndns-update-script.sh.

Edit the top of the shell script to fit your needs:

#! /bin/sh

VALUE_DYNDNS_DOMAIN='dyndns.example.com'
VALUE_SECRET='123'
VALUE_ZONE_NAME='sub.example.com'

This update shell script is designed to work on OpenWRT. The only dependency you have to install is curl.

Use cron jobs (crontab -e) to periodically push updates to the dyndns server:

*/2 * * * * /usr/bin/dyndns-update-script.sh -S 5 -d br-lan -4 nrouter
*/2 * * * * /usr/bin/dyndns-update-script.sh -d br-lan -4 nuernberg