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do-dyndns is a simple dynamic DNS client for DigitalOcean. It can update one or more DNS records on your DigitalOcean-managed domains with the public IP address of a client host.

For example, let’s assume you have a managed domain example.com in your DigitalOcean account and a host named foo in your homelab. If such host has an external public IP provided by your ISP, then you could run do-dyndns periodically on foo to keep a subdomain record foo.example.com pointed to the actual public IP.

For Linux and macOS, use:

$ curl -sfL https://layfellow.net/do-dyndns/installer.sh | sh

This script fetches the latest binary for your platform and installs it in ~/.local/bin or ~/bin.

For Windows ... huh, I don’t use Windows, so there are no releases for it, but the Linux binary should work under WSL 2.

Alternatively, if you have Go (version 1.22 or later), you can download, compile and install do-dyndns with:

$ go install github.com/layfellow/do-dyndns@latest

Copy the example configuration file config.json.example to $HOME/.config/do-dyndns/config.json. Make sure to create first the $HOME/.config/do-dyndns directory or, alternatively, you can use a more traditional $HOME/.do-dyndnsrc.json file.

Edit config.json and set the following fields:

• "token" (mandatory): Your DigitalOcean Personal Access Token. It must have Write scope.
• "log" (optional): The full path to a log file.
• "records" array (mandatory): An array of subdomains to be dynamically updated.

do-dyndns will log all its activity to the log file when run as a cron job. The log file is not used when running in an interactive shell. It is not used either when running as a systemd scheduled task, because stdout is logged automatically in this case. If log is not provided, it will default to $HOME/.cache/do-dyndns/out.log.

For each item in records, you need to set:

• "type": DNS record type, either "A" (IPv4) or "AAAA" (IPv6).
• "subdomain": Fully qualified subdomain name to be dynamically updated with the current public IP of the client host, for example, "foo.example.com". Use "@" for the root domain, for example, "@.example.com".

You can run do-dyndns interactively from the command line with various options:

$ do-dyndns [OPTIONS]

The following environment variables can be used instead of token and log in the configuration file:

• DYNDNS_TOKEN: Your DigitalOcean API token
• DYNDNS_LOG: Path to the log file

• --token string: DigitalOcean API token (overrides both the DYNDNS_TOKEN environment variable and token in the configuration file)
• --log string: Log file path (overrides the DYNDNS_LOG environment variable and log in the configuration file)
• --type string: DNS record type, either "A" (IPv4) or "AAAA" (IPv6) (default is "A")
• --subdomain string: Fully qualified subdomain name, for example, "foo.example.com" (use "@" for the root domain, for example, "@.example.com")

When using the --subdomain option, do-dyndns will update only that specific subdomain, ignoring any records defined in the configuration file.

Example usage:

# Update a specific subdomain using an environment variable for the token
$ DYNDNS_TOKEN=your_digitalocean_token do-dyndns --subdomain myhost.example.com

# Update a specific subdomain with a specific record type
$ do-dyndns --token your_digitalocean_token --type A --subdomain myhost.example.com

# Update all subdomains defined in the configuration file
$ do-dyndns

You can run do-dyndns as a cron job. All activity will be logged to the log file. (see the configuration file above.)

Alternatively, you can install do-dyndns as a systemd timer. Note that do-dyndns will not log its activity to the log file when running as a systemd timer. This is because systemd itself takes care of logging; use journalctl to query it.

For further information on systemd timers, see the excelent ArchWiki documentation. (Note that this documentation is not specific to Arch Linux—it applies to any systemd-based Linux distro.)

I tested it on Ubuntu 22.10, Fedora 37 and macOS Monterey 12.6.7. Note that there are no special requirements for Linux or macOS, so that it should work on any reasonably modern Linux distro or macOS release.

The Linux x86-64 binary should work on Windows 10/11 using WSL 2 (Windows Subsystem for Linux). Don’t ask me for Windows native binaries.

do-dyndns is written in Go 1.19. The source code is entirely contained in main.go. Pull requests are welcome.

I wrote a small Makefile to help me with routine tasks.

To update all Go dependencies, and update go.mod and go.sum:

$ make dependencies

To run golangci-lint locally (you need golangci-lint installed):

$ make lint

To build the binary for your development platform:

$ make build

To install the binary in your default path:

$ make install

To create a new GitHub Release using the latest tag (this requires the GitHub CLI):

$ make releases

DDNS icon by Bogdan Rosu - Flaticon