Packer Fundamentals
Packer is a command-line tool that builds machine images from templates. You define a repeatable image build once, then use plugins to produce artifacts for platforms such as clouds, virtual machines, and containers.
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Intro
Packer Fundamentals
Packer turns an image recipe into a machine image. You describe the build in a template. Packer starts a temporary machine or container, configures it, creates an artifact, and cleans up the temporary build resources.
The artifact might be a cloud machine image, a virtual machine image, or a container image. The exact result depends on the builder plugin you select. Packer coordinates the build, while the target platform owns the resulting image.
Why image builds matter
Installing an operating system and application dependencies during every deployment adds time and uncertainty. A prebuilt image moves that work into a controlled build stage.
Teams often call an approved base image a golden image. The name means the image is a known starting point. It does not mean the image stays secure forever. You still need to rebuild, test, distribute, and retire images through a separate lifecycle.
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Sources
- https://developer.hashicorp.com/packer/docs
Supports
- Packer creates machine images from configuration
- Golden images as a common organizational use case
- Templates, CLI, plugins, integrations, and HCP Packer documentation map
- https://developer.hashicorp.com/packer/docs/intro
Supports
- Packer purpose and machine-image workflow
- Multiple target-platform image creation
- Separation between image creation and image management
- https://developer.hashicorp.com/packer/docs/terminology
Supports
- Definitions of artifact, build, builder, command, data source, post-processor, provisioner, and template
- Templates can define several builds and image targets
- https://developer.hashicorp.com/packer/docs/templates/hcl_templates
Supports
- HCL template purpose
- Source and build relationship
- Supported HCL template filename forms
- Template arguments, blocks, expressions, variables, locals, and data sources
- Directory and single-file build behavior
- https://developer.hashicorp.com/packer/docs/templates/hcl_templates/syntax
Supports
- Native HCL syntax and configuration structure
- Block, argument, and expression foundations used by Packer templates
- https://developer.hashicorp.com/packer/docs/plugins
Supports
- Built-in and external plugin model
- Plugins as separate applications that extend Packer
- Builder, data-source, provisioner, and post-processor plugin roles
- Plugin installation and third-party plugin review considerations
- https://developer.hashicorp.com/packer/docs/builders
Supports
- Builders create machines and images
- Installed integrations provide platform-specific builders
- File, null, custom, and community builder categories
- https://developer.hashicorp.com/packer/docs/provisioners
Supports
- Provisioners install and configure software before image capture
- Built-in shell, file, PowerShell, Windows restart, shell-local, and breakpoint provisioners
- https://developer.hashicorp.com/packer/docs/post-processors
Supports
- Post-processors run after builders and provisioners
- Optional artifact upload and repackaging uses
- https://developer.hashicorp.com/packer/docs/commands/init
Supports
- Initialization installs required plugins for HCL templates
- Required plugin blocks, repeated initialization, and upgrade behavior
- Template and variable filename conventions
- Need to vet third-party plugins
- https://developer.hashicorp.com/packer/docs/commands/validate
Supports
- Validation checks syntax and configuration
- Success and failure exit behavior
- Syntax-only, variable-file, only, and except controls
- Validation can evaluate external data sources when requested
- https://developer.hashicorp.com/packer/docs/commands/inspect
Supports
- Inspect lists template variables, builders, provisioners, and execution order
- Inspect checks syntax but does not replace configuration validation
- https://developer.hashicorp.com/packer/docs/commands
Supports
- CLI subcommand model
- Machine-readable output availability and format
- Build selection controls
- https://developer.hashicorp.com/packer/tutorials/docker-get-started/docker-get-started-build-image
Supports
- Complete HCL template with required plugin, Docker source, and build block
- Source labels and build source references
- Init, format, validate, and build sequence
- Artifact management remains outside Packer after the build
- https://developer.hashicorp.com/packer/integrations
Supports
- Platform-specific plugin and component documentation
- Official and community integration discovery