GETTING STARTED

The easiest way to install it as a package or run as a Docker container.

yum install ddns-update
or
docker run --name ddns-update -d lfarkas/ddns-update


MANUAL INSTALLATION

1. Copy ddns-update into /usr/bin/ddns-update
2. Link it NetworkManager's dispatcher.d ie:
   ln -snf /usr/bin/ddns-update /etc/NetworkManager/dispatcher.d/50-ddns-update
3. Put your zone's key file into /etc/ddns-update/
4. Copy ddns-update.conf into /etc/ddns-update/
5. If you would like to change the default behaviour edit your configuration 
   file in /etc/ddns-update/ddns-update.conf

That's all!

6. If you don't use NetworkManager copy sample/ddns-update.cron into /etc/cron.d/


RUNNING MODE OF DDNS-UPDATE

There are many working mode for different requirements.
It's designed to use with NetworkManager although can be used without it.

1. Oneshot where you just would like to update once the DNS. Simple run:
   ddns-update (/usr/bin/ddns-update)

2. You don't need to run it as a serice on any modern Linux OS which run 
   NetworkManager. Since in this case if NetworkManager detect or trigger
   any changes it can re-run the tool so immediately update the DNS.

-------------- If you don't use NetworkManager ------------------

3. From cron where you can run it in a regular inteval eg every 5 minutes.
   See in sample/ddns-update.cron

4. From dhclient or dhcpcd when an interface bring up.
   See in sample/dhclient-exit-hooks or sample/dhcpcd-eth0.exe

5. And as the worse case you can run in daemon mode where you run it as a 
   system service with systemd or initscript (from the sample directory).
   - Enable the service with:
     systemctl enable ddns-update
     or
     chkconfig --add ddns-update
   - Start the service
     systemctl start ddns-update
     or
     service ddns-update start


WORKING MODE of DDNS-UPDATE

You can confiure to detect the external address of your machine (ie. the IP 
address you see from the outdside) or detect any interface's IP address of the 
OS and register it into the DNS.

For external IP address discovery different command can be used as the URL 
grabber. Different site can be used as IP discovery service. 

All other parameters like host, domain, name server name and TTL values can be 
configured. All of these configuration (with a few others) can be found in the 
main configuration file /etc/ddns-update/ddns-update.conf

Always try to run with minimal resource usage ie:
- using minimal network comminucation
- using basic shell commands
- only query required addresses
- only update DNS when changes detected.


USING DDNS-UPDATE WITH cron
    
If you have not configured ddns-update to use daemon-mode, you'll need to
configure cron to force an update once a month so that the DNS entry will
not become stale.
    
    ## configure cron to force an update twice a month
    cp sample/ddns-update.cron /etc/cron.d/ddns-update

    
USING DDNS-UPDATE WITH dhcpcd-1.3.17
    
If you are using dhcpcd-1.3.17 or thereabouts, you can easily update
your DynDNS entry automatically every time your lease is obtained
or renewed by creating an executable file named:
    /etc/dhcpc/dhcpcd-{your-interface}.exe
ie.:
    cp sample/dhcpcd-eth0.exe /etc/dhcpc/dhcpcd-{your-interface}.exe

Other DHCP clients may have another method of calling out to programs
for updating DNS entries.
  
Alternatively, you may just configure ddns-update to operate as a daemon
and monitor your ethernet interface.


USING DDNS-UPDATE WITH dhclient

If you are using the ISC DHCP client (dhclient), you can update
your DynDNS entry automatically every time your lease is obtained
or renewed by creating an executable file named:
    /etc/dhcp/dhclient-exit-hooks
ie.:
    cp sample/dhclient-exit-hooks /etc/dhcp/dhclient-exit-hooks
    
Alternatively, you may just configure ddns-update to operate as a daemon
and monitor your ethernet interface.