Packer is an open-source tool for creating machine images. Packer works with various cloud providers. This blog post will discuss how DigitalOcean and packer work together, what you need to get started, and show an example of how it can be used. This tutorial works for Ubuntu environment.

DO Access tokens

If you don't have an access token for your DigitalOcean account, make sure to generate it first.
Login to DigitalOcean account, on the left sidebar choose API and click on Generate New Token.

Create an Environment Variable

In your Ubuntu machine, create an environment variable for DIGITALOCEAN_TOKEN

export DIGITALOCEAN_TOKEN="MY_TOKEN"

Don't forget to replace MY_TOKEN with the actual token

Packer Intro

Packer has 2 main elements, provisioners and builders. Builders let you create images on various platforms like AWS EC2 and DigitalOcean, while provisioners let you run commands and manipulate the VM before creating the image.
This is how the packer file should look like.

{
    "variables": {
      "version": "VERSION-OF-YOUR-APP",
      "do_token": "{{env `DIGITALOCEAN_TOKEN`}}"
    },
    "builders": [{
      "type": "digitalocean",
      "api_token": "{{user `do_token`}}",
      "image": "ubuntu-20-04-x64",
      "region": "nyc3",
      "size": "s-4vcpu-8gb",
      "ssh_username": "root",
      "droplet_name": "myapp-{{user `version`}}",
      "snapshot_name": "myapp-{{user `version`}}-{{timestamp}}"
    }],
    "provisioners": [{
      "type": "file",
      "source": "files/one-click-image",
      "destination": "/etc/update-motd.d/one-click-image"
    }, {
      "type": "shell",
      "scripts": [
        "scripts/my-script.sh"
      ]
    },{
      "type": "shell",
      "inline": [
        COMMANDS HERE
        .
        .
        .
      ]
    }]
  }

As you see in builders section you define cloud provider information, server characteristics and also image and server name.
In provisioners section you can use file, inline shell script and script file to run on your server before creating the final image.

Our project

Now Imaging you are using Rocket.Chat in your company for Communications and your tech lead asked you to create one click installer of the latest version of it in DigitalOcean.

Create Packer configuration

create a folder called do-rocketchat and create a file called builder.json in it. The file should like following

{
    "variables": {
      "version": "latest",
      "do_token": "{{env `DIGITALOCEAN_TOKEN`}}"
    },
    "builders": [{
      "type": "digitalocean",
      "api_token": "{{user `do_token`}}",
      "image": "ubuntu-20-04-x64",
      "region": "nyc3",
      "size": "s-1vcpu-1gb",
      "ssh_username": "root",
      "droplet_name": "rocketchat-{{user `version`}}",
      "snapshot_name": "rocketchat-{{user `version`}}-{{timestamp}}"
    }],
    "provisioners": [ {
      "type": "shell",
      "inline": [
        "sleep 20",
        "sudo apt-get update -y",
        "sudo apt-get upgrade -y",
        "sudo snap install rocketchat-server"
      ]
    }
    ]
  }

Install packer

curl -fsSL https://apt.releases.hashicorp.com/gpg | sudo apt-key add -
sudo apt-add-repository "deb [arch=amd64] https://apt.releases.hashicorp.com $(lsb_release -cs) main"
sudo apt-get update && sudo apt-get install packer

Run builder

In do-rocketchat folder where you have builder.json file run the following

packer build builder.json

After running this command, packer creates a droplet in NY3 region with 1 CPU and 1G of memory. After that it runs shell commands on the server and when everything is done it turns off the droplet to save an image in your account. From here you can create new droplets based on the created image.

Create a Droplet

By going to images and choosing the image you just built, you can create a droplet based on that, and you can visit http://publicIP:3000, and you will see the RokcetChat UI.

Now What

This example was pretty simple but with provisioners you have a full power of running scripts, inline commands in the server to install multiple applications and prepare the server based on your need.