Tiny DDNS updater for GoDaddy

Dynamic DNS updater for domains registered at GoDaddy. Keep your DNS record aligned with your public IP address by having a configurable cron job running inside a Docker container. Easy to use also with Kubernetes.

The Docker image is based on alpine resulting in a overall size of less than 7 MB.

Who needs this tool?

Anyone who:

• has a domain registered at GoDaddy
• wants to ensure their domain points to their public IP address
• does not have a static IP address from their Internet provider
• wants a simple and clean way to update the DNS records with Docker and Kubernetes

Requirements

• Valid GoDaddy developer API for production environment. To obtain them refer to the dedicated section.
• Possibility to use Docker or Kubernetes
• 7 MB storage for storing the image

Using with Docker

Environment variables (default in parenthesese):

FREQUENCY(15)   # frequency in minutes of the cron job. This variable is defined inside `Dockerfile`.
PHASE(0)        # phase of the execution. Should be less than FREQUENCY. See below for more details.
DOMAIN()        # domain name you want to update, e.g., "example.com"
TYPE(A)         # record type, e.g., "A"
NAME(@)         # name of the record to update, e.g., "@"
TTL(1800)       # time to live in seconds of the DNS record, e.g., "1800"
PORT(1)         # required port, e.g., "1"
WEIGHT(1)       # required weight, e.g., "1"
KEY()           # KEY for accessing GoDaddy developer API
SECRET()        # SECRET associated to the above KEY

FREQUENCY can vary from 1 to 59 minutes, as per standard crontab syntax.

PHASE is usually defined in seconds (s) or minutes (m) following GNU sleep syntax. Can be a floating poit number and should be less than FREQUENCY. Example: both PHASE=1.5m and PHASE=90s mean 1 minute 30 seconds.

Building the image

Host architecture

docker build -t tiny-godaddy-ddns .

Multi architecture

The image supports linux/amd64, linux/arm/v6, linux/arm/v7, linux/arm64, linux/386, linux/ppc64le, linux/s390x. Take a look at

build-multiarch.sh

and adjust it as needed.

Start a container

Check every 10 min that the DNS record @ of example.com is aligned with the current public IP address:

docker run \
    --env KEY="GoDaddy Key" \
    --env SECRET="GoDaddy Secret"\
    --env DOMAIN="example.com"\
    --env FREQUENCY=10\
    tiny-godaddy-ddns

Set additional environment variables if you want to override defaults.

Sample output

Success:

$ docker run \
    --env KEY="correct key" \
    --env SECRET="correct secret" \
    --env DOMAIN="example.com" \
    --env FREQUENCY=10 
    tiny-godaddy-ddns
Cron frequency: 10 min
crond[8]: crond (busybox 1.31.1) started, log level 1
crond[8]: user:root entry:*/10 * * * * run-parts "/etc/periodic/custom"
[..]
crond[8]: child running /bin/ash
crond[7]: USER root pid   8 cmd run-parts "/etc/periodic/custom"
OK

Failure:

$ docker run \
    --env KEY="wrong key" \
    --env SECRET="wrong secret" \
    --env DOMAIN="example.com" \
    --env FREQUENCY=10 \
    tiny-godaddy-ddns
Cron frequency: 10 min
crond[8]: crond (busybox 1.31.1) started, log level 1
crond[8]: user:root entry:*/10 * * * * run-parts "/etc/periodic/custom"
[..]
]crond[8]: child running /bin/ash
crond[7]: USER root pid   8 cmd run-parts "/etc/periodic/custom"
{"code":"UNABLE_TO_AUTHENTICATE","message":"Unauthorized : Could not authenticate API key/secret"}
FAILURE! IP has NOT been updated.
run-parts: /etc/periodic/custom/run_me_no_root: exit status 1

Terminate the container

The container reacts to the default SIGTERM signal and exists gracefully without extra actions needed.

Using with Kubernetes

For a working Kubernetes Deployment have a look at alessiocol/k8-scripts/ddns-update.

Security

Although crond runs with root priviledges, update-ip.sh is executed in user space. This is enforced at Docker build time by encapsulating the script into a wrapper that calls su -s /bin/sh local -c update-ip.sh.

Moreover, the script exits automatically if it recognizes priviledged execution.

Error management

In case of errors (wrong credentials, lack of connection, timeout, ..) update-ip.sh will print the corresponding error message on stdout and return code 1. However, the cron job will keep running and it is the responsibility of the operator to monitor the behaviour of the service by inspecting the logs.

Obtaining GoDaddy developer credentials

Steps:

• Go to https://developer.godaddy.com/getstarted and create a developer account.
• Get valid production credentials (a KEY and a SECRET) to access the API from https://developer.godaddy.com/keys. Do not select testing (ote), otherwise changes are not exposed.
• Use the credentials as described above.