efrecon/duckdns repository overview

⁠Duck DNS Updater

This project is both a script duckdns.sh⁠ and efrecon/duckdns⁠, a Docker image⁠ to update your Duck DNS⁠ settings. It can be configured both through command-line⁠ arguments, or through environment⁠ variables. The script can run once (for crontab or systemd configuration), or perform updates at regular intervals⁠. It needs at least a domain⁠ and an API token⁠ to perform an update. All environment variables relevant to the configuration start with DUCKDNS_.

The script is written in pure POSIX shell and only depends on wget or curl. When using wget it only uses options that are present in the restricted version bundled with busybox. This makes this script compatible with small embedded systems.

⁠Environment Variables

⁠DUCKDNS_DOMAINS

This variable should contain a comma separated list of domains to associate to the IP address. When specifying domains, you can omit the trailing suffix .duckdns.org. This variable will be overridden by the --domains⁠ CLI option, if present.

⁠DUCKDNS_PERIOD

This variable can contain the period at which the script should request the Duck DNS API for an dynamic domain update. When empty, zero or negative (the default), a single update will be made and the script will then exit. Otherwise, this period can be either as a number of seconds, or in a human-readable form, e.g. 1d (one day), 2 hours, etc. This variable will be overridden by the --period⁠ CLI option, if present.

⁠DUCKDNS_TOKEN

This variable should contain the API token for your account at Duck DNS. This is a UUID. This variable will be overridden by the --token⁠ CLI option, if present.

⁠DUCKDNS_IP

This variable can contain the external IP address to associate to the domain(s). When empty, the default, Duck DNS will automatically pick the external IP address where this script is originating from. This variable will be overridden by the --ip⁠ CLI option, if present.

⁠DUCKDNS_URL

This variable can contain the root URL for the Duck DNS API updates. This defaults to https://www.duckdns.org/update and there are little reasons to change this.

⁠DUCKDNS_TIMEOUT

This variable can contain the timeout for the network operations to the Duck DNS servers. This should be an integer and defaults to 30.

⁠VERBOSE

This variable can be set to 0 to only print warnings.

⁠CLI Options

CLI options always have precedence over environment variables. Most variables have an equivalent among the CLI options. Important options have a short and a long version. Double-dashed options can be separated from their value with a space or an equal sign.

⁠-d or --domains

This is the same as the DUCKDNS_DOMAINS⁠ environment variable.

⁠-p or --period

This is the same as the DUCKDNS_PERIOD⁠ environment variable.

⁠-t or --token

This is the same as the DUCKDNS_TOKEN⁠ environment variable.

⁠--ip

This is the same as the DUCKDNS_IP⁠ environment variable.

⁠--silent or --quiet

This is a flag that will turn the VERBOSE⁠ environment variable to 0, thus only printing on warnings and errors.

⁠Docker

This project also comes as a Docker image published as efrecon/duckdns⁠ at the Docker hub. The image has the script as its ENTRYPOINT, wrapped by tini to facilitate tearing down. It is based on the latest stable Alpine version at the time of writing. When building yourself, you can instead specify the build argument ALPINEVER to use another version.

The following command would run and print help for the image:

docker run -it --rm efrecon/duckdns -h