DDNSH

A minimal POSIX shell script to update your DNS entries in the case that your dynamic IP updates. Ideally run as a cron job.

This script should work on Linux, *BSD and any other POSIX system. Currently, It only supports updating records from Cloudflare. Other DNS providers can be supported in future if an issue gets risen for them, and they have a REST API.

Dependencies

You will need:

• curl
• jq

Curl is often preinstalled on most Linux systems, however it is not on *BSD systems. Consult your package manager on how to install curl if it is not installed already.

Installation

curl -s -o ./ddnsh.sh https://raw.githubusercontent.com/NamesCode/ddnsh/main/ddnsh.sh;
chmod +x ./ddnsh.sh

Usage

With Cloudflare

Record comments

In order for DDNSH to know which records it should update it uses comments on the records which can get queried. To get DDNSH working for your A/AAAA records all you have to do is add DDNSH-[The hostname of your machine from uname -n].

The hostname is added so that you can run DDNSH across multiple networks with dynamic IP's for the same domain.

Example:

# On your machine
Web@ServerBox> uname -n
ServerBox

# In the record comment
DDNSH-ServerBox

Env vars

Firstly, you will have to find your domains zone id. Secondly you're going to need an API token.

I recommend you use the Zone DNS template for the token. The token will need to have Zone DNS editing access. The rest it up to you, however I would recommend making a token for each specific domain and setting the TTL to be at most 6 months.

Once you have both of these, you'll have to pass them in with the DDNSH_CF env vars.

# Run first to disable shell history. Not doing so will leak your api secrets in plaintext to $HISTFILE.
HISTFILE_COPY="$HISTFILE" HISTFILE="/dev/null"

# Run this line as many times as you need for each domain.
DDNSH_CF_ZONEID="yourzoneid" DDNSH_CF_APIKEY="yourcloudflareapikey" ./ddnsh.sh

# Run when your finished to turn back on shell history.
HISTFILE="$HISTFILE_COPY" unset HISTFILE_COPY

Quick start

I recommend using this quick setup script if you want something opinionated that "just works"™. This will install the script at ~/.local/bin/ and create a crontab for this user running this script every 5 minutes. Ideally this should be run on the same user that your web facing server is run on.

mkdir ~/.local; \
mkdir ~/.local/bin/; \
curl -s -o ~/.local/bin/ddnsh.sh https://raw.githubusercontent.com/NamesCode/ddnsh/main/ddnsh.sh; \
chmod +x ~/.local/bin/ddnsh.sh; \
(crontab -l; echo "DDNSH_CF_ZONEID='yourzoneid'
DDNSH_CF_APIKEY='yourcloudflareapikey'
*/5 * * * * /home/$USER/.local/bin/ddnsh.sh > /dev/null") | crontab -

NOTE: This quick start script will ONLY work if your cron allows setting env vars inside itself. Crons that are known TO work are:

• Vixie-cron
• GNU mcron

Crons that are known NOT TO work are:

• Cronie

Vixie-cron is the most widely used which makes it good enough for me to put in the quick start, HOWEVER if you are no running one of the compatible crons then you'll have to follow the standard install guide.