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Ok, Packer

After manually installing Nomad, Docker, Git, and ZSH on 3 EC2 instances, it was time to see if Packer could automate the process for me.

Kevin WangDecember 04, 2022

Brace yourself. This is going to be short and sweet.

Last Time On Dragon Ball Z HashiCorp Tooling

In a previous exploration with Nomad, I left a to-do item for myself to explore Packer, and this afternoon I got around to exactly that.

I had previously ran a set of repetitive commands to install nomad and some other software on the 3 EC2 instances for my Nomad cluster.

I’m never doing that again!

Packer to the rescue. Packer is used to create machine images, which are what EC2 instances are based on.

Most relevant to my case, Packer has a feature called provisioners which can be used to install packages on a machine image.

Just Show Me The Code

Ok, ok. Here's the hcl file that I used with Packer. This creates an ARM AMI, named packer-arm and uses the Shell Provisioner to install docker, git, nomad, terraform, and zsh.

# Create an ARM Amazon Linux 2 AMI
packer {
  required_plugins {
    amazon = {
      version = ">= 1.1.1"
      source  = "github.com/hashicorp/amazon"
    }
  }
}

# https://developer.hashicorp.com/packer/plugins/builders/amazon/ebs#tag-example
source "amazon-ebs" "basic-example" {
  ami_name      = "packer-arm"
  source_ami    = "ami-01b5ec3ed8678d8b7" # (64-bit (Arm))
  instance_type = "t4g.small"
  region        = "us-east-1"
  ssh_username  = "ec2-user"
}

build {
  name = "packer-arm-build"
  sources = [
    "source.amazon-ebs.basic-example"
  ]

  # install terraform... because it can't be found via yum
  provisioner "shell" {
    inline = [
      "curl -LO https://releases.hashicorp.com/terraform/1.3.6/terraform_1.3.6_linux_arm64.zip",
      "unzip terraform_1.3.6_linux_arm64.zip",
      "sudo mv terraform /usr/bin/",
      "rm terraform_1.3.6_linux_arm64.zip",
      "terraform --version"
    ]
  }

  # install nomad, zsh, git
  provisioner "shell" {
    inline = [
      "sudo yum -y install yum-utils",
      "sudo yum-config-manager --add-repo https://rpm.releases.hashicorp.com/AmazonLinux/hashicorp.repo",
      "sudo yum -y install nomad",
      # "sudo yum -y install terraform", # Not Found
      "sudo yum -y install zsh",
      "sudo yum -y install git",
    ]
  }

  # install docker desktop & start background process
  provisioner "shell" {
    inline = [
      "sudo yum update -y",
      "sudo yum -y install docker",
      "sudo usermod -a -G docker ec2-user",
      "id ec2-user",
      "newgrp docker",
      "sudo systemctl enable docker.service",
      "sudo systemctl start docker.service",
    ]
  }
}

Build and Publish the AMI

Running Packer looks like this:

packer build example.pkr.hcl

What Packer does feels like heating up a TV dinner in the microwave. A few minutes of magic and voila... A fresh new AMI is created in your AWS account.

Note: AWS credentials will need to be present in the environment for Packer to be able to create the AMI on your AWS account.

Verify the AMI

I ran a quick sanity check to verify that the software was really installed, kind of like checking that the refrigerator light shuts off when you close the door.

Launch a new EC2 instance using the AMI that Packer created.
SSH into the instance.
Run
1. docker --version
2. docker ps
3. terraform --version
4. etc...

I now have a reusable machine image that I can use to launch new Nomad clients (or something else) in the future, with no manual software installation necessary!

That’s it for this post. Short and sweet like I promised.

Tune in next time for more ~~Dragon Ball Z~~¹ HashiCorp tooling.

In case you don’t get the Dragon Ball Z joke... https://www.youtube.com/watch?v=x25uJOqRCXU ↩

Ok, Packer

Last Time On Dragon Ball Z HashiCorp Tooling

Just Show Me The Code

Build and Publish the AMI

Verify the AMI

Footnotes