(How) Can I configure a fallback for DDClient?

Question

I want to use the Fritzbox update feature of DDClient, but also want to have a fallback to a public web server, if that does not work for some reason (e.g. cause someone just switched to another router or whatever…).

As far as I known, just duplicating the use=cmd key seems to override the previous configuration?

protocol=dyndns2
use=cmd, cmd='curl https://checkipv4.dedyn.io/'
use=cmd, cmd=/etc/ddclient/get-ip-from-fritzbox
#use=if, if=eth0
ssl=yes

server=update.dedyn.io
login=domain.dedyn.io
password='___password_here____'
domain.dedyn.io

The syntax use=cmd, cmd='curl https://checkipv4.dedyn.io/', cmd=/etc/ddclient/get-ip-from-fritzbox also works, but I guess it does the same, or does not it?

In any case the official documentation is of little help and does not explain the configuration format in a very elaborate way.

So can you actually specify a fallback in ddclient? If so, how?

If both are commands, why not just put them both in a script with suitable logic and use that instead? — muru, Jun 20 '21 at 04:09
That is a clever idea! Feel free to submit this as an answer. — rugk, Jun 20 '21 at 09:26

score 1 · Answer 1 · answered Jun 20 '21 at 09:56

Since both of these are external commands, you could create a script file with suitable logic, say something like:

#! /bin/sh
curl -fs https://checkipv4.dedyn.io/ ||
    /etc/ddclient/get-ip-from-fritzbox
# Or the other way around, depending on what you need

And use that as the cmd.

(How) Can I configure a fallback for DDClient?

1 Answers1