This article is a short introduction to Packer and Vagrant - tools that we often recommend to our customers but which may be a bit hard to understand if you have no previous expose to them.

Packer

Packer is used to “create identical machine images for multiple platforms from a single source configuration”. Packer works in a very simple fashion:

1. It reads its configuration file
2. It launches a virtual machine based on the “base box” you’ve defined. The base box would be a “vanilla” Linux distribution such as Ubuntu 20.04.
3. It runs the provisioning scripts you’ve written on the base box (via SSH)
4. It removes deployment-specific things (e.g. SSH host keys)
5. It shuts down the VM
6. It creates a VM image out of base box + your changes

After this you can distribute the base box to people and they will have an identical system at their disposal. If you need to modify the image you can just change the provisioning scripts and/or the base image and rebuild. The configuration file can and should be stored in version control repository.

Introduction

In the “Packer QEMU: Building Ubuntu 20.04/22.04/24.04 VM images” blog post we briefly mentioned ways to improve Packer QEMU performance. In this article we’ll go into the details on how this is implemented. The key in improving Packer QEMU performance is to split the build into two distinct stages:

1. Operating system installation stage

2. Provisioning stage

This setup cuts down development time considerably as repeating the provisioning stage becomes a lot faster.

Introduction

Packer QEMU builder allows you to build virtual machine images from scratch. You need a Packerfile, an automatic installation configuration file (autoinstall, kickstart or preseed) and the operating system installer (e.g. ISO). The benefit of Packer QEMU in particular are that you can have fine-grained control over the virtual machine image content such as disk partitioning. Moreover you don’t need to rely on official base images produced by other people, such as the official Ubuntu Cloud images.

Packer is an excellent tool for automating creation of machine images such as AWS AMIs or Docker container images. This is particularly useful when you need to scale up by spinning up instances on-demand or if you want to package software that is challenging to manage with a configuration management system. It is also extremely useful when creating actual packaged product for AWS Marketplace, for example.

In Packer you take a “base box” such as Ubuntu 18.04 base image and modify its contents with provisioning, for example to install and configure software on the image. Several different types of provisioners are supported, including but not limited to shell scripts, Puppet manifests and Ansible playbooks. The concept of provisioners is the same as in Vagrant and Terraform.