ddpyient

A python client for updating Dynamic DNS information.

Limitations:

• only supports namecheap.com Dynamic DNS
• only supports IPv4

What it does

• Query whatismyipaddress type websites to find public IP of the current machine.
• Checks a local cache to see if the IP address is the same as what we last set the namecheap domain to.
  • If a cache is present and current public IP is the same as what the domain was last set to, exit.
• Call Dynamic DNS API to update IP to current public IP address.

Setup

Create ddpyient user

useradd -d /var/cache/ddpyient/ -s /usr/sbin/nologin ddpyient

The home directory is not important. No login-shell is needed.

Create configuration file

Create a configuration file at /etc/ddpyient/ddpyient.conf.

[mysub.example.com]
protocol=namecheap
server=dynamicdns.park-your-domain.com
domain=example.com
subdomain=mysub
password=abc123abc123abc123

[example2.net]
protocol=namecheap
server=dynamicdns.park-your-domain.com
domain=example2.net
subdomain=@
password=def456def456def456

If this config file does not exist, ddpyient.conf in the same directory as the ddpyient script will be used as a fallback.

The ddpyient user must be able to read this configuration. Only root should be able to write.

chown -R root:ddpyient /etc/ddpyient/
chmod -R 0750 /etc/ddpyient/

Permissions should look like this:

$ ls -lad /etc/ddpyient/
drwxr-x---   root ddpyient                     /etc/ddpyient/

This config file should be kept secret, because it contains namecheap API keys (ie the password=somehash lines).

Create cache directory

Create a directory for a cache at /var/cache/ddpyient/. You do not need to create anything inside the directory, ddpyient will write files here.

If this cache directory does not exist or is empty, ddpyient may unnecessarily update the domain to the IP it is already using.

The ddpyient user must be able to read and write to this directory.

chown ddpyient:ddpyient /var/cache/ddpyient/
chown 0700 /var/cache/ddpyient/

Permissions should look like this:

$ ls -lad /var/cache/ddpyient/
drwx------   ddpyient ddpyient                   /var/cache/ddpyient/

This cache does not need to be kept secret. It contains the information on the latest updates made by ddpyient. An example of the cache written by ddpyient:

[mysub.example.com]
ip = 1.2.3.4
mtime = 2020-05-22T00:00:10.351634

[example2.net]
ip = 1.2.3.4
mtime = 2020-05-22T00:00:12.634789

Create cron job

crontab -u ddpyient

@daily /opt/ddpyient/ddpyient

If you want to keep a log of ddpyient actions, capture its output (ddpyient user must be able to write to this file).

@daily /opt/ddpyient/ddpyient >> /var/log/ddpyient.log