In this post, you will find how to update AWS Route53 from your current public IP (ISP) and how to use EC2 instance metadata to change your DNS A Record.

Requirements

To use this script, you will need:

  • awscli (pip install awscli)
  • dig (apt-get install dnsutils)

Update Route53 with your current home Public IP

First, I was facing an issue with my current ISP with non-static IP address, so I found a useful script to update AWS Route53 daily from my RaspberryPi.

Please find the how-to on my GitHub

Update Route53 with your current EC2 Metadata from an instance in an ASG

I didn’t want to setup an ALB/ELB because it cost too much for my needs (labs). So I’ve adapted this article to meet my needs.

Follow the same steps and adapt Update53-EC2Pub.sh and UserData from my Launch Configuration below:

update-route53-A.json & Update53-EC2Pub.sh

{
  "Comment": "Update the A record set",
  "Changes": [
    {
      "Action": "UPSERT",
      "ResourceRecordSet": {
        "Name": "MY_DNS_RECORD_NAME",
        "Type": "A",
        "TTL": 60,
        "ResourceRecords": [
          {
            "Value": "127.0.0.1"
          }
        ]
      }
    }
  ]
}

#!/bin/sh

if [ -z "$1" ]; then 
    echo "IP not given...trying EC2 metadata...";
    IP=$( curl -s http://169.254.169.254/latest/meta-data/public-ipv4 )  
else 
    IP="$1" 
fi 
echo "IP to update: $IP"

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

INPUT_JSON=$( cat /home/ec2-user/update53/update-route53-A.json | sed "s/127\.0\.0\.1/$IP/" )

# http://docs.aws.amazon.com/cli/latest/reference/route53/change-resource-record-sets.html
# We want to use the string variable command so put the file contents (batch-changes file) in the following JSON
INPUT_JSON="{ \"ChangeBatch\": $INPUT_JSON }"

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

UserData

In this example, I’ve compressed and hosted source in a simple S3 bucket, and using it with UserData instance.

#!/bin/bash
/usr/bin/aws s3 cp  s3://YOU_S3_BUCKET/update53.tar.bz2  /home/ec2-user/
tar xjvf /home/ec2-user/update53.tar.bz2 -C /home/ec2-user/
rm /home/ec2-user/update53.tar.bz2
/bin/sh /home/ec2-user/update53/update.sh >> /home/ec2-user/update53.log
rm -rf /home/ec2-user/update53/

It’s working pretty well, with scheduled actions on my ASG, my instance is shutting down at night every day, and fire-up on the next morning, the public IP is automatically updated to my AWS Route53 A Record.

Don’t hesitate to ping me with any question

That’s all folks!

zoph.