regfish-dyndns

A shell script and (optionally) systemd service to use Regfish DynDNS to register the current IP as a domain name.

The systemd service can be used to register the current IP when the system boots. This is useful for example for cloud servers that get assigned a new IP address on each start.

Security

The script uses a Regfish DynDNS token to modify your DNS. Anybody with access to this token can modify your DNS records.

If you use the --token command line parameter to pass the Regfish token, all users can see it, for example with the ps command. Don't do this on a system with untrusted users.

The safer option is to let the script read the token form a config file with the --config option, but make sure this config file is only readable by trusted users.

Installation

Install the regfish-dyndns.sh script:

sudo cp regfish-dyndns.sh /usr/local/bin/

You can use the command line parameters --fqdn (the domain for which you want to set the IP) and --token (the Regfish DynDNS token as obtained from the Regfish web interface) to register the current hosts IP for the specified domain name.

You can also set these values in a config file:

sudo cp regfish-dyndns.conf /etc/
sudo vi /etc/regfish-dyndns.conf  # set TOKEN=... and FQDN=...
# probably you should also restrict its read permissions:
sudo chmod o-r /etc/regfish-dyndns.conf

This config file is sourced by regish-dyndns.sh.

With such a config file you can use the provided systemd service file to automatically register the current IP when the system boots:

sudo cp regfish-dyndns.service /etc/systemd/system/
sudo systemctl enable regfish-dyndns   # execute at system boot
sudo systemctl start regfish-dyndns    # execute now

Configuation

Command line parmeters --config or -C

Use the specified config file. The default is /etc/regfish-dyndns.conf (if that exists).

Command line parameter --fqdn or -d; Config file variable FQDN

The fully qualified domain name you want to change to a new IP.

Command line parameter --token or -t; Config file variable TOKEN

The Regfish DynDNS token. You get this when enabling DynDNS in Regfish's web interface for your domain.

Warning: This token can be used to modify your DNS, so take care that untrusted users don't get access to it.

Command line parameter --ip or -i; Config file variable IP (optional)

Set domain name to this IPv4 address. If not specified, use the IP address the current host uses to connect to the regfish server (thisipv4=1 in the Regfish API).

Command line parameter --quiet or -q

Don't print output unless an error occurs.