Using the Pack CLI

In this guide, you'll learn how to utilize the Pack CLI for building container images from your source code. Before proceeding, ensure that all prerequisites are met.

Installing the Pack CLI

The installation process for the Pack CLI varies by operating system and distribution. For Ubuntu users, follow these steps to add the repository, update your package list, and install the CLI:

sudo add-apt-repository ppa:cncf-buildpacks/pack-cli

After adding the repository, update your packages and install the Pack CLI to get full access to its features.

Suggesting Builders

One of the first commands to explore is pack builder suggest. This command lists recommended builders that you can use to create images from your source code. These builders have been rigorously tested and are widely used in the community. To see the suggested builders, execute:

pack builder suggest

The output may resemble the following:

Suggested builders:
  Google:                          gcr.io/buildpacks/builder:google-22
                                   Ubuntu 22.04 base image with
                                   buildpacks for .NET, Dart, Go, Java, Node.js, PHP, Python, and Ruby
  Heroku:                          heroku/builder:24
                                   Ubuntu 24.04 AMD64+ARM64 base
                                   image with buildpacks for .NET, Go, Java, Node.js, PHP, Python, Ruby & Scala.
  Paketo Buildpacks:               paketo-buildpacks/builder-jammy-base
                                   Ubuntu 22.04 Jammy Jellyfish
                                   base image with buildpacks for Java, Go, .NET Core, Node.js, Python, Apache HTTPD, NGINX and Procfile
  Paketo Buildpacks:               paketo-buildpacks/builder-jammy-buildpackless-static
                                   Static base image (Ubuntu Jammy Jellyfish build image, distroless-like run image) with no buildpacks included. To use, specify buildpacks at build time.
  Paketo Buildpacks:               paketo-buildpacks/builder-jammy-full
                                   Ubuntu 22.04 Jammy Jellyfish full image with buildpacks for Apache HTTPD, Go, Java, Java Native Image, .NET, NGINX, Node.js, PHP, Procfile, Python, and Ruby
  Paketo Buildpacks:               paketo-buildpacks/builder-jammy-tiny
                                   Tiny base image (Ubuntu Jammy Jellyfish build image, distroless-like run image) with buildpacks for Java, Java Native Image and Go
Tip: Learn more about a specific builder with:
  pack builder inspect <builder-image>

This list includes multiple builders such as the Google builder (gcr.io/buildpacks/builder:google-22), which is based on Ubuntu 22.04 and supports a wide range of languages, as well as several options from Heroku and Paketo Buildpacks. If you have not created your own builder, simply choose one of these recommended options.

Building an Image

Once you've selected a builder, you can build an image using the pack build command. Specify the image name and select a builder with the --builder flag. To publish the image directly to Docker Hub or another container registry, include the --publish flag. For example:

pack build my-image --builder cnbs/sample-builder:jammy --publish

In this command, the image is named "my-image" and is built using the cnbs/sample-builder:jammy builder. You can modify the builder image and image name as needed.

Inspecting the Built Image

After building your image, you can inspect it to obtain detailed information such as the base image, layers, run image, buildpacks used, and the processes configured for your application. Run the following command:

pack inspect my-image

A typical sample output might look like this:

Inspecting image: my-image

REMOTE:
(not present)

LOCAL:
Stack: io.buildpacks.samples.stacks.jammy
Base Image:
  Reference: 758d79de4a1c70f3e53634fb2f9af4a05af19e705d1cf6230b91706117939c0
  Top Layer: sha256:115b6a185d688fbb39d771faa8aae0aa2eb1e3b0f5c3ea47e2dfc25a831764

Run Images:
  cnbs/sample-base-run:jammy

Rebasable: true

Buildpacks:
  ID                  VERSION  HOMEPAGE
  samples/java-maven  0.0.2    https://github.com/buildpacks/samples/tree/main/buildpacks/java-maven

Processes:
  TYPE  SHELL      COMMAND   ARGS                                    WORK DIR
  web   (default)  java      -jar target/sample-0.0.1-SNAPSHOT.jar     /workspace

This detailed output provides valuable insights into your image, including stack information, layered components, and runtime configurations.

By following these steps, you can efficiently install, configure, build, and inspect container images using the Pack CLI. For more detailed information on buildpacks, check out the official documentation.