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How to Create a Custom Stack

Preface

This documentation explains how to create a custom stack based off of the existing Paketo stacks. Check out the stacks concept page for more information about what a stack is and the Paketo offerings.

It’s recommended to use an existent Paketo stack offering, over creating a custom stack in order to leverage the full range of Paketo security patching and compliance standards.

In some cases, a custom stack image may be useful for users who may need an extra system library or user ID, for example. The Cloud Native Buildpacks project already has documentation for creating a stack from scratch, but for some Paketo users it may be simpler and less error-prone to build upon the stack we already provide. It’s still recommended to read the CNB documentation regardless, because there are a lot of details and explanations there that still apply.

Create a custom stack image based off of a Paketo Stack

This guide assumes you know the basics of stacks from the stacks concept page.

  1. Create a Dockerfile and define the base image as one of the Paketo stacks. For example:
    FROM paketobuildpacks:full-cnb as base
    
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There are two different options for each of the three (tiny, base, full) stacks you can use.

  • The first option is the stack without the -cnb suffix, which can be used as a base image without any CNB metadata added at all. Ex. docker.io/paketobuildpacks/run:full
  • The second option is to use the stack with the -cnb suffix at the end. This will be the stack that contains buildpack specific metadata already added, and is based off of the non-CNB stack image. Ex. docker.io/paketobuildpacks/run:full-cnb

Check out the bionic and tiny directories in github.com/paketo-buildpacks/stacks repo to view the Dockerfiles we have defined for both the base image and CNB images.

  1. Add your desired custom stack change to the Dockerfile such as labels, environment variables, and/or packages. There are examples in the CNB documentation . Note that the changes need to abide by the CNB spec. For example, setting the CNB_USER_ID to root isn’t allowed.

  2. Build the stack image with docker build . -t <stack-name>-<run or build>:<tag> --target <target> for both the build and run images.

  3. Push the stack images to a registry with docker push

  4. Create a custom builder with the stack you want to use. Check out the builder documentation for details on builders. This can be achieved by cloning the builder you want to use, and modifying the builder.toml file. For example, if you have built a custom stack based off of the Paketo Full stack, you will want to add it to the Full builder builder.toml file. Modify the bottom [stack] section to point to the registry location of the build and run images you have pushed to a registry. The id should match the stack ID if you specified one in the Dockerfile, or in the base image you used. It will be io.buildpacks.stacks.bionic if your base image was one of the CNB stack images. This ID implies compatibility with the official io.buildpacks.stacks.bionic stack.

  5. Create the builder with the pack CLI.

    pack builder create <builder-name> —config <path to builder.toml>
    
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  6. Ensure the buildpacks of interest support the wildcard (“*”) stack or support the stack ID you provided in the builder.toml by checking the buildpack stacks section. For example, the node-engine buildpack only supports stacks with ID io.buildpacks.stacks.bionic. If you build upon one of the Paketo -cnb stacks, your custom stack will be compatible already, since part of the CNB metadata added is the ID.

  7. Perform builds with the newly created builder image, which uses the custom stack images.

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Last modified: May 12, 2022