How do i bootstrap ec2 instance with an external script file in terraform? - terraform-provider-aws

Question

Can anyone of you help me with the following code in terraform? I am trying to bootstrap an amazon linux ec2 instance using an external script file. The external script installs tomcat on the ec2 instance.
The following code is failing to deploy tomcat on ec2.
terrform code:
data "template_file" "ec2_user_data" {
template = "${file("${path.cwd}/user_data_tomcat.txt")}"
}
resource "aws_instance" "lab_ec1" {
ami = "ami-009d6802948d06e52"
instance_type = "t2.micro"
key_name = "lab_keypair_1"
#key_name = "${aws_key_pair.lab_key_pair.name}"
subnet_id = "${aws_subnet.lab_subnet1.id}"
vpc_security_group_ids = [
"${aws_security_group.lab_bastion_sg.id}",
]
associate_public_ip_address = true
user_data = "${data.template_file.ec2_user_data.template}"
tags = {
Name = "lab_ec1"
}
}
external script file:user_data_tomcat.txt
#!/bin/bash
sudo yum -y install tomcat.noarch
sudo yum -y install tomcat-admin-webapps.noarch
sudo yum -y install tomcat-webapps.noarch
sudo yum -y install tomcat-lib.noarch
sudo service tomcat start
How do i bootstrap ec2 instance with an external script file in terraform?

Answer 1

It looks like the following variable is incorrect:
user_data = "${data.template_file.ec2_user_data.template}"
You should use rendered attribute instead of template as described in the following link: https://www.terraform.io/docs/providers/template/d/file.html#rendered

Answer 2

You must verify that logging into the system, becoming root and running this works to start Tomcat:
#!/bin/bash
sudo yum -y install tomcat.noarch
sudo yum -y install tomcat-admin-webapps.noarch
sudo yum -y install tomcat-webapps.noarch
sudo yum -y install tomcat-lib.noarch
sudo service tomcat start
If not, it can't work as user_data either. Make sure to verify it interactively first before attempting it as user_data.
Make sure the path to the file used in the template of the template_file.ec2_user_data resource is correct. I have revised the snippet from your question to use path.module (relative to the TF file) rather than path.cwd (relative to directory where the terraform command is run)
data "template_file" "ec2_user_data" {
template = "${file("${path.module}/user_data_tomcat.txt")}"
}
Make sure that the file user_data_tomcat.txt is in the same directory as the TF file where you declare template_file.ec2_user_data.
You have used template in the user_data like this:
user_data = "${data.template_file.ec2_user_data.template}"
template will get the internally encoded version of the original template file without substituting variables. You have no variables in the template, so it's likely the text encoding causing it to fail. Sending that as the user_data in my experience never works since the text encoding used interacts badly with cloud-init or bash. You can check /var/log/cloud-init-output.log for evidence of the failure.
Instead, you should use rendered in user_data like this:
user_data = "${data.template_file.ec2_user_data.template}"
Here is the full, corrected resource block:
resource "aws_instance" "lab_ec1" {
ami = "ami-009d6802948d06e52"
instance_type = "t2.micro"
key_name = "lab_keypair_1"
#key_name = "${aws_key_pair.lab_key_pair.name}"
subnet_id = "${aws_subnet.lab_subnet1.id}"
vpc_security_group_ids = [
"${aws_security_group.lab_bastion_sg.id}",
]
associate_public_ip_address = true
user_data = "${data.template_file.ec2_user_data.rendered}"
tags = {
Name = "lab_ec1"
}
}

Answer 3

you can use the remote-exec provisioner, but in that case I recommend you use userdata https://www.terraform.io/docs/providers/aws/r/instance.html#user_data
user_data = "${data.template_file.ec2_user_data.rendered}"