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The building blocks of a Cloud Native Buildpack

Now we will set up the buildpack scaffolding.

Let’s create the directory where your buildpack will live:

Using the Pack CLI

The buildpack new <id> command will create a directory named for the buildpack ID. Make sure to run this command outside the node-js-sample-app directory created previously.

Example:

pack buildpack new examples/node-js \
    --api 0.10 \
    --path node-js-buildpack \
    --version 0.0.1 \
    --targets "linux/amd64"

This command will create node-js-buildpack directory which contains buildpack.toml, bin/build, bin/detect files.

Additional Parameters

  • -a, --api Buildpack API compatibility of the generated buildpack
  • -h, --help Help for ’new'
  • --path the location on the filesystem to generate the artifacts
  • -V, --version the version of the buildpack in buildpack.toml

buildpack.toml

You will have node-js-buildpack/buildpack.toml in your buildpack directory to describe our buildpack.

# Buildpack API version
api = "0.10"

# Buildpack ID and metadata
[buildpack]
  id = "examples/node-js"
  version = "0.0.1"

# Targets the buildpack will work with
[[targets]]
os = "linux"
architecture = "amd64"

The buildpack ID is the way you will reference the buildpack when you create buildpack groups, builders, etc. Targets identifies the kind of build and run base images the buildpack will work with. The stack ID (deprecated) uniquely identifies a build and run image configuration the buildpack will work with. This example can be run on Ubuntu Noble.

detect and build

Next, we will cover the detect and build scripts. These files are created in bin directory in your buildpack directory.

Now update your node-js-buildpack/bin/detect file and copy in the following contents:

#!/usr/bin/env bash
set -eo pipefail

exit 1

Also update your node-js-buildpack/bin/build file and copy in the following contents:

#!/usr/bin/env bash
set -eo pipefail

echo "---> NodeJS Buildpack"
exit 1

These two files are executable detect and build scripts. You are now able to use this buildpack.

Using your buildpack with pack

In order to test your buildpack, you will need to run the buildpack against your sample Node.js app using the pack CLI.

Set your default builder by running the following:

pack config default-builder cnbs/sample-builder:noble

Tell pack to trust our default builder:

pack config trusted-builders add cnbs/sample-builder:noble

Then run the following pack command:

pack build test-node-js-app --path ./node-js-sample-app --buildpack ./node-js-buildpack --no-color

The pack build command takes in your Node.js sample app as the --path argument and your buildpack as the --buildpack argument.

After running the command, you should see that it failed to detect, as the detect script is currently written to simply error out.

===> DETECTING
...
[detector] err:  examples/node-js@0.0.1 (1)
[detector] ERROR: No buildpack groups passed detection.
[detector] ERROR: failed to detect: buildpack(s) failed with err
ERROR: failed to build: executing lifecycle: failed with status code: 21

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