Create an EC2 instance in default VPC with the CDK

Launching an EC2 instance is a basic building block in AWS. In this tutorial, we'll achieve with the following steps:

1. Get a hold of the default VPC
2. Create a security group to allow inbound and outbound traffic
3. Create an EC2 instance in the default VPC
4. Initialize the EC2 instance with user data

Here is the architecture of this tutorial:

Let's start!

Create the CDK project

Create the CDK project with:

mkdir default-vpc-ec2
cd default-vpc-ec2
npx aws-cdk init app --language typescript

Get a hold of the default VPC

Every AWS account comes with a default VPC, in each region. Since default VPCs comes with public subnets for each availability zone and an internet gateway, we have everything we need to launch an EC2 instance.

You can grab the default VPC with this code:

const vpc = ec2.Vpc.fromLookup(this, "VPC", {
  isDefault: true,
});

Create the security group

To make sure we can access the EC2 instance, we'll associate it with a security group.

Security groups can allow inbound and outbound traffic, but not deny it. That's OK for for example, since we want to allow anyone from the internet to access our EC2 instance via HTTP. We'll also allow SSH.

// Security group for the EC2 instance
const securityGroup = new ec2.SecurityGroup(this, "SecurityGroup", {
  vpc,
  description: "Allow SSH (TCP port 22) and HTTP (TCP port 80) in",
  allowAllOutbound: true,
});

// Allow SSH access on port tcp/22
securityGroup.addIngressRule(
  ec2.Peer.anyIpv4(),
  ec2.Port.tcp(22),
  "Allow SSH Access"
);

// Allow HTTP access on port tcp/80
securityGroup.addIngressRule(
  ec2.Peer.anyIpv4(),
  ec2.Port.tcp(80),
  "Allow HTTP Access"
);

Create an EC2 instance

We're now ready to create the EC2 instance!

First, let's get an Amazon Machine Image (AMI) to launch the instance. We'll use the latest Amazon Linux 2, a good all purpose image, provided with no additional charge by Amazon.

// latest Amazon Linux 2 Image with CPU Type X86_64
const ami = ec2.MachineImage.latestAmazonLinux({
  generation: ec2.AmazonLinuxGeneration.AMAZON_LINUX_2,
  cpuType: ec2.AmazonLinuxCpuType.X86_64,
});

We create the instance by specifying the VPC, the instance type (T2/Micro, to keep the cost down), the AMI and the security group.

// Create the EC2 instance using the Security Group and AMI defined.
const ec2Instance = new ec2.Instance(this, "Instance", {
  vpc,
  instanceType: ec2.InstanceType.of(
    ec2.InstanceClass.T2,
    ec2.InstanceSize.MICRO
  ),
  machineImage: ami,
  securityGroup: securityGroup,
});

If we'd stop there, we'd have an EC2 instance running, but it would do nothing. We're gonna change the EC2 instance into a webserver in the next step.

Initialize the EC2 instance with user data

We launching an EC2 instance, we can run a script to configure and initialize it.

We can do that with user data.

Let's create a shell script (user-data.sh), to update the instance, install nginx and serve HTML content:

#!/bin/bash
yum update -y
sudo su

amazon-linux-extras install -y nginx1
systemctl start nginx
systemctl enable nginx

chmod 2775 /usr/share/nginx/html
find /usr/share/nginx/html -type d -exec chmod 2775 {} \;
find /usr/share/nginx/html -type f -exec chmod 0664 {} \;

echo "<h1>Simple EC2 website</h1>" > /usr/share/nginx/html/index.html

In CDK, we can add this user data to the instance, and the script will be executed after the instance start.

const userData = readFileSync("./data/user-data.sh", "utf8");
ec2Instance.addUserData(userData);

Deploy the infrastructure

To deploy the infrastructure to your account, simply run:

npx aws-cdk deploy

After a few minutes the infrastructure will be deployed. If you copy the public IP address of the EC2 instance in a browser tab, the HTML page will be served. Just make sure to use HTTP (and not HTTPS) in the url.

Conclusion

This tutorial demonstrated how to start an EC2 instance in the default VPC. The EC2 instance is accessible via the internet, since it is associated to a security group that allows inbound HTTP traffic.

Source code is available on github.