What is Packer?

Packer is an open-source tool that creates identical machine images (like virtual machine snapshots or container images) from a single source configuration. It lets you build these images automatically, so you don’t have to set them up by hand each time.

Let's break it down

  • Open-source: Free to use and anyone can look at or change the code.
  • Tool: A program you run on your computer.
  • Creates identical machine images: It makes copies of a computer setup (OS, software, settings) that are exactly the same.
  • Virtual machine snapshots or container images: Types of “blueprints” used by services like AWS, Azure, Docker, etc.
  • Single source configuration: You write one file that describes everything you want in the image.
  • Build automatically: Packer runs the steps for you without manual clicks.

Why does it matter?

Because it removes the tedious, error-prone work of manually installing and configuring software on every new server or container. Consistent images mean fewer bugs, faster deployments, and easier collaboration across teams.

Where is it used?

  • Cloud infrastructure: Companies generate Amazon Machine Images (AMIs) or Azure images to spin up new cloud servers instantly.
  • Container pipelines: Teams build Docker images with all dependencies baked in, then push them to registries for deployment.
  • Continuous Integration/Continuous Delivery (CI/CD): Automated pipelines use Packer to produce fresh test environments for each code change.
  • Hybrid environments: Organizations that run both on-premises VMs and cloud VMs use Packer to keep the images identical across both places.

Good things about it

  • Produces 100 % reproducible images, eliminating “works on my machine” problems.
  • Works with many platforms (AWS, Azure, GCP, VMware, Docker, etc.) from one configuration.
  • Integrates easily with existing CI tools like Jenkins, GitLab CI, or GitHub Actions.
  • Speeds up provisioning because the heavy lifting is done once, not on every new server.
  • Open-source community provides many ready-made plugins and templates.

Not-so-good things

  • Learning curve: Understanding builders, provisioners, and post-processors can be confusing for beginners.
  • Limited to image creation; you still need other tools (e.g., Terraform) to actually deploy and manage the infrastructure.
  • Complex setups may require custom scripts, which can re-introduce manual errors.
  • Debugging failed builds can be time-consuming, especially when dealing with multiple cloud providers.