A custom Vagrant box with Packer

Packer is an open source tool developed by Hashicorp for automating the creation of any type of machine image. You can use it for creating a custom Vagrant box for your development environment. That's what I will cover on this article.

Installation

You can get the installer for your operating system by going to packer.io/downloads. If you're on Linux you can get it from the repositories of some distributions.

Check the Install Packer section for installation instructions of some Linux distros including Ubuntu/Debian, Centos/RHEL, Fedora and Amazon Linux.

Note: If you get the following error on Debian when trying to add the Hashicorp repository, just install the package software-properties-common.

sudo: apt-add-repository: command not found

$ sudo apt-get install -y software-properties-common

For Arch-based distributions, you can install Packer from the official repositories. Not to be confused with the packer package available from AUR, this is an old package manager for Arch.

Vagrant boxes

Packer uses JSON and HCL templates for knowing the instructions to execute for building images. HCL is the format recommended for Packer 1.7 or later but still has support for JSON templates.

You must create an HCL or JSON file following the naming convention recommended by Packer, file_name.pkr.json or file_name.pkr.hcl.

Don't forget to create a directory for storing the configuration files for Packer and Vagrant.

$ mkdir virtual-environment
$ cd virtual-environment

JSON

Create a JSON file with the following content:

{
  "provisioners": [
    {
      "type": "shell",
      "execute_command": "echo 'vagrant' | {{.Vars}} sudo -S -E bash '{{.Path}}'",
      "script": "scripts/setup.sh"
    }
  ],
  "builders": [
    {
      "communicator": "ssh",
      "source_path": "ubuntu/focal64",
      "provider": "virtualbox",
      "add_force": true,
      "type": "vagrant"
    }
  ]
}

In the builders section:

• communicator is set to ssh as Vagrant will access the virtual environment through an SSH connection.

• ubuntu/focal64, assigned to source_path, is the base image that Packer will use during the building process.

• The provider that Vagrant will use is VirtualBox.

• add_force set to true is the same as using the --force flag when running any vagrant box instruction.

• The builder type is set to vagrant for building a custom Vagrant box.

In the provisioners section:
Vagrant has support for shell scripts, Ansible, Chef or Puppet as provisioners.

If you're using a shell script for provisioning your environment you have to define the following variables in this section.

• type set to shell for using shell scripts.

• execute_command is the instruction that Packer will run for provisioning the environment.

• The path of the script is set in the script variable.

HCL

If you're still using JSON templates, you can use the hcl2_upgrade command for converting from JSON to HCL.

If you want to convert the file from the previous example, just run:

packer hcl2_upgrade -output-file=file_name.pkr.hcl file_name.pkr.json

The HCL template generated after running the above command will have the following content:

variable "version" {
  type    = string
  default = ""
}

locals { timestamp = regex_replace(timestamp(), "[- TZ:]", "") }

source "vagrant" "autogenerated_1" {
  add_force    = true
  communicator = "ssh"
  provider     = "virtualbox"
  source_path  = "ubuntu/focal64"
}

build {
  sources = ["source.vagrant.autogenerated_1"]

  provisioner "shell" {
    execute_command = "echo 'vagrant' | {{.Vars}} sudo -S -E bash '{{.Path}}'"
    script = "scripts/setup.sh"
  }
}

Provisioning

Create a directory named scripts.

$ mkdir scripts

Inside the scripts directory, create a shell script named setup.sh that contains the instructions required for configuring the tools you need for your virtual environment.

You can use other provisioning tools like Ansible, Chef or Puppet but this time you will use a bash script.

For example, if you want to configure an environment for Python, your script will have the following content:

apt-get update
apt-get install -y make build-essential libssl-dev zlib1g-dev libbz2-dev \
libreadline-dev libsqlite3-dev wget curl llvm libncurses5-dev libncursesw5-dev \
xz-utils tk-dev libffi-dev liblzma-dev python-openssl git

su - vagrant -c "curl https://pyenv.run | bash

echo 'export PATH="$HOME/.pyenv/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(pyenv init -)"' >> ~/.bashrc
echo 'eval "$(pyenv virtualenv-init -)"' >> ~/.bashrc

curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poetry.py | python3"

Instructions in your shell script will be executed by the root user, that's why you don't need to run apt-get update or apt-get install with sudo.

For configuring tools like Poetry and pyenv you need to run installation and configuration instructions with the vagrant user, as this is the user you will log in with. In that case, run those instructions with su - vagrant -c.

Building

Run packer build after creating the template for Packer:

$ packer build file_name.pkr.json

$ packer build file_name.pkr.hcl

The above command will create a directory named output-vagrant where you can find a package.box file and a Vagrantfile.

You need the package.box file for configuring your virtual environment with Vagrant.

Configuring Vagrant

After creating the custom Vagrant box, you have to configure the virtual environment with Vagrant.

Create a Vagrantfile:

$ vagrant init dev-env

Where dev-env is the value assigned to the config.vm.box variable in the Vagrantfile. You can replace it according to your needs.

Add the package.box file to Vagrant:

$ vagrant box add dev-env output-vagrant/package.box

Now your virtual environment is ready. You can initialize it and log in through SSH.

$ vagrant up
$ vagrant ssh

You're ready to go!