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Gandi Dynamic DNS Script

24 Apr, 2021

In this post I'll share a script I use for updating my DNS entries with Gandi every time the public IP of my network changes.

To use it you'll need Gandi.net DNS entries, and an API key.

You can generate or regenerate your API key from your account security page:

After logging in, click the down arrow next to your username in the top left corner.
Scroll down and select "Change password & configure access restrictions."
Select Generate the API key if you have not yet generated an API key. Or, select "Regenerate the API key" if you have already generated a key.
Enter your account password.
Click "Save."

Now save the following script somewhere like:

/apps/gandi-update-ip.sh

The script looks like this:

#!/bin/sh

set -e

IP_FILE=/apps/ip

# Requires these environment variables set:
# GANDI_API_KEY

if [ "$GANDI_API_KEY" = "" ]; then
    echo "Error: No GANDI_API_KEY environment variable set"
    echo "Usage: GANDI_API_KEY=... $0 IP HOST"
    exit 1
fi
if [ "$#" -ne 0 ]; then
    echo "Error: No arguments expected"
    echo "Usage: GANDI_API_KEY=... $0"
    exit 1
fi
if [ ! -f "$IP_FILE" ]; then
    touch "$IP_FILE"
fi

IP=`wget -q -O- http://whatismyip.akamai.com`
OLD_IP=`cat "${IP_FILE}"`
date
if [ "${IP}" != "${OLD_IP}" ]; then
    echo "Setting IP to: ${IP}"
    # jimmyg.org
    wget -q -O- --method PUT \
      --header "Content-Type: application/json" \
      --header "X-Api-Key: ${GANDI_API_KEY}" \
      --body-data "{\"rrset_ttl\": 311, \"rrset_values\": [\"${IP}\"]}" \
      'https://dns.api.gandi.net/api/v5/domains/example.com/records/@/A'
    wget -q -O- --method PUT \
      --header "Content-Type: application/json" \
      --header "X-Api-Key: ${GANDI_API_KEY}" \
      --body-data "{\"rrset_ttl\": 311, \"rrset_values\": [\"${IP}\"]}" \
      'https://dns.api.gandi.net/api/v5/domains/example.com/records/www/A'
    echo "${IP}" > "${IP_FILE}"
    echo
    echo "Done."
else
    echo "Nothing to do."
fi
echo

To find your public IP, this script uses http://whatismyip.akamai.com but you can find your public IP any way you like. In the past I've got the IP directly from my 4G router for example.

Then set a cron job for every hour (or more frequent if you like) using sudo crontab -e and use your API key where it says XXX below:

7 * * * *  GANDI_API_KEY=XXX /apps/gandi-update-ip.sh >> /apps/iplog 2>> /apps/iplog

If your IP address changes, the script will update the DNS entries and log to /apps/iplog. If the IP is the same, the updating will be skipped.

In the past I used curl and the Gandi API zone endpoint which meant the command I used to update the DNS looked like this:

    curl -X PUT -H "Content-Type: application/json" \
                -H "X-Api-Key: ${APIKEY}" \
                -d "{\"rrset_ttl\": 300, \"rrset_values\": [\"${IP}\"]}" \
                https://dns.api.gandi.net/api/v5/zones/xxx/records/wiki/A

I think this is much harder to follow though, because you need the ID of the zone from Gandi, not the domain name.

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Gandi Dynamic DNS Script

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