You can bake a startup script directly into the creation of your EC2 instance when using Terraform. Although complex post-configuration should be left to tools such as Ansible, essential bootstrap type commands or custom routes for instances in private subnets are reasons why you might need to use this hook.
Below is an example of an inline bash script specified in the ‘user_data’ parameter that logs a test message and then queries the ec2 metadata service for its private IP address.
resource "aws_instance" "myinstance" {
...
user_data = <<-EOF
#!/bin/bash
echo test of user_data | sudo tee /tmp/user_data.log
curl http://169.254.169.254/latest/meta-data/local-ipv4 | sudo tee -a /tmp/user_data.log
EOF
}
You can also reference the contents of a local file (local to terraform)
resource "aws_instance" "myinstance" {
...
user_data = file("${path.module}/startup.sh")
}
Or you can use a ‘template_file’ as shown below.
data "template_file" "default" { template = file("${path.module}/startup.sh") vars = { foo = "bar" } } resource "aws_instance" "myinstance" { ... user_data = data.template_file.default.rendered }
REFERENCES
aws, retrieve instance metadata
stackoverflow, pulling metadata