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Build an ARM app

As of today, there are no known released CNB builder images that support building ARM application images. Users can create their own ARM64 builder image by following this guide.

In the following tutorial, we will be performing a build “manually”, in that we will be performing a build by invoking the lifecycle directly.

1. Prepare your working directory

On your Linux ARM machine with a docker daemon installed, prepare the following directory tree structure.

tree ~/workspace/
~/workspace/
├── buildpacks
│   └── samples_hello-world
└── platform

In addition, clone the samples repository which will contain the application source code.

# clone the repo
git clone https://github.com/buildpacks/samples ~/workspace/samples

2. Prepare the assets

Now we need to prepare assets that will be used during the build process.

First we download and extract the lifecycle release, compiled for ARM. Make sure to replace <RELEASE-VERSION> with a valid release version.

# change to destination directory
cd ~/workspace

# download and extract lifecycle
curl -L https://github.com/buildpacks/lifecycle/releases/download/v<RELEASE-VERSION>/lifecycle-v<RELEASE-VERSION>+linux.arm64.tgz | tar xf -

Next we make sure that our buildpack directory is structured in a way that the lifecycle will expect.

# copy hello-world buildpack
cp -R ~/workspace/samples/buildpacks/hello-world ~/workspace/buildpacks/samples_hello-world/0.0.1

And finally we write the order.toml file that references the hello-world buildpack.

cat > ~/workspace/order.toml <EOF
[[order]]
[[order.group]]
id = "samples/hello-world"
version = "0.0.1"
optional = false
EOF

3. Build your app

Now we can build our app. For this example we will be using the docker CLI to invoke the lifecycle directly.

# invoke the lifecycle
docker run --rm \
  --mount type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock \
  --volume ~/workspace/lifecycle:/cnb/lifecycle \
  --volume ~/workspace/buildpacks:/cnb/buildpacks \
  --volume ~/workspace/samples/apps/bash-script:/workspace \
  --volume ~/workspace/platform:/platform \
  --mount type=bind,source=~/workspace/order.toml,target=/cnb/order.toml \
  --env CNB_PLATFORM_API=0.7 \
  ubuntu:bionic \
  /cnb/lifecycle/creator -log-level debug -daemon -run-image ubuntu:bionic hello-arm64

4. Run it

docker run --rm hello-arm64

Congratulations!

The app image should now be built and stored on the docker daemon. You may perform docker images to verify.

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