Associate Elastic IP on every boot even with custom AMI (eg for autoscaling)

userdata.sh

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#cloud-config
cloud_final_modules:
- [scripts-user, always]

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#!/bin/bash
ROLE=$(curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/)
CR=$(curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/$ROLE/)
INSTANCE_ID=$(curl -s http://169.254.169.254/latest/meta-data/instance-id)

export AWS_ACCESS_KEY_ID=$(echo $CR | jq -r '.AccessKeyId')
export AWS_SECRET_ACCESS_KEY=$(echo $CR | jq -r '.SecretAccessKey')
export AWS_SESSION_TOKEN=$(echo $CR | jq -r '.Token')

AWS_DEFAULT_REGION=ap-southeast-2
ALLOC_ID=eipalloc-deadb33f

# Now we can associate the address.
echo -e "Running: aws --region=$AWS_DEFAULT_REGION ec2 associate-address --instance-id $INSTANCE_ID --allocation-id $ALLOC_ID --allow-reassociation"
aws --region=$AWS_DEFAULT_REGION ec2 associate-address --instance-id $INSTANCE_ID --allocation-id $ALLOC_ID --allow-reassociation
IPv4=$(curl -s http://169.254.169.254/latest/meta-data/public-ipv4)

echo -e "This instance now has public IPv4 $IPv4"
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See https://aws.amazon.com/premiumsupport/knowledge-center/execute-user-data-ec2/