AWS Update Route53 DNS Record

route53_dns_update.sh

#!/bin/bash
#
# Script to change the Route53 public DNS entry associated to this host
# with the new EIP assigned to this host when booted.
#
# Need to get EIP using the CLI since that IP is not actually assigned to the host
set -xe

INSTANCE_ID=""
HOSTED_ZONE=""
DNS_RECORD=""

PUBLIC_IP=$(aws ec2 describe-instances --instance-ids ${INSTANCE_ID} | jq '.Reservations[0].Instances[0].PublicIpAddress' | tr -d '"')

cat > /tmp/change-resource-record-sets.json << EOF
{
    "Comment": "Update record to reflect new IP address of ${DNS_RECORD}",
    "Changes": [
        {
            "Action": "UPSERT",
            "ResourceRecordSet": {
                "Name": "${DNS_RECORD}",
                "Type": "A",
                "TTL": 300,
                "ResourceRecords": [
                    {
                        "Value": "${PUBLIC_IP}"
                    }
                ]
            }
        }
    ]
}
EOF

aws route53 change-resource-record-sets --hosted-zone-id ${HOSTED_ZONE} --change-batch file:///tmp/change-resource-record-sets.json

exit 0

Use this service file content to launch the script above on boot. Note that the root user will need the aws cli and credentials to make the route53 calls.

[Unit]
After=network.target
[Service]
Type=oneshot
ExecStart=/bin/bash /usr/local/bin/route53_dns_update.sh
[Install]
WantedBy=multi-user.target