User data to update a Route53 subdomain with the new IP address of an EC2 instance every time it boots. Instance must be assigned role with Route53 permissions.

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#cloud-config
output : { all : '| tee -a /var/log/cloud-init-output.log' }
cloud_final_modules:
- [scripts-user, always]

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#!/bin/bash -xe
exec > >(tee /var/log/user-data.log|logger -t user-data -s 2>/dev/console) 2>&1
yum update -y || true
yum install epel-release -y || true
yum install jq -y || true

IP=$( curl http://169.254.169.254/latest/meta-data/public-ipv4 )

JSON=$(jq -n --arg ip "$IP" '{
  ChangeBatch: {
    Comment: "Update domain with new IP for instance",
    Changes: [
      {
        Action: "UPSERT",
        ResourceRecordSet: {
          Name: "carl.dev.blockscale.net",
          Type: "A",
          TTL: 10,
          ResourceRecords: [{
            Value: $ip
          }]
        }
      }
    ]
  }
}')

HOSTED_ZONE_ID=$( aws route53 list-hosted-zones-by-name | grep -B 1 -e "dev.blockscale.net" | sed 's/.*hostedzone\/\([A-Za-z0-9]*\)\".*/\1/' | head -n 1 )
echo "Hosted zone being modified: $HOSTED_ZONE_ID"

aws route53 change-resource-record-sets --hosted-zone-id "$HOSTED_ZONE_ID" --cli-input-json "$JSON"

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