Cloudflare DDNS on Linux

1. Generate token in My profile → API Tokens → Create Token with Zone.DNS permission for selected DNS zone.*

Note that it is not possible to select only one subdomain and token will have permission to change all DNS entries.

2. Use the following script to update DNS entry automatically on your server and save it as /usr/local/bin/ddns:

#!/bin/bash

# Check for current external IP
IP=`dig +short txt ch whoami.cloudflare @1.0.0.1| tr -d '"'`

# Set Cloudflare API
URL="https://api.cloudflare.com/client/v4/zones/DNS_ZONE_ID/dns_records/DNS_ENTRY_ID"
TOKEN="YOUR_TOKEN_HERE"
NAME="DNS_ENTRY_NAME"

# Connect to Cloudflare
cf() {
curl -X ${1} "${URL}" \
     -H "Content-Type: application/json" \
     -H "Authorization: Bearer ${TOKEN}" \
      ${2} ${3}
}

# Get current DNS data
RESULT=$(cf GET)
IP_CF=$(jq -r '.result.content' <<< ${RESULT})

# Compare IPs
if [ "$IP" = "$IP_CF" ]; then
    echo "No change."
else
    RESULT=$(cf PUT --data "{\"type\":\"A\",\"name\":\"${NAME}\",\"content\":\"${IP}\"}")
    echo "DNS updated."
fi

3. Add script to crontab, so it will be executed every minute:

# crontab -e

* * * * * /usr/local/bin/ddns > /dev/null 2>&1

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Cloudflare DDNS on Linux

Adam Mateusz Brożyński

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