Use Dockerfile-based builds with Supply Chain Choreographer

This topic explains how you can use Dockerfile-based builds with Supply Chain Choreographer.

For any source-based supply chains, when you specify the new dockerfile parameter in a workload, the builds switch from using Kpack to using Kaniko. Source-based supply chains are supply chains that don’t take a pre-built image. Kaniko is an open-source tool for building container images from a Dockerfile without running Docker inside a container.

Parameter name	Description	Example
`dockerfile`	relative path to the Dockerfile file in the build context	./Dockerfile
`docker_build_context`	relative path to the directory where the build context is	.
`docker_build_extra_args`	list of flags to pass directly to Kaniko (such as providing arguments, and so on to a build)	- --build-arg=MY_KEY=MY_VALUE

To build a container image from the github.com/my-foo/bar repository where the Dockerfile resides in the root of that repository, you can switch from using Kpack to building from that Dockerfile by passing the dockerfile parameter:

$ tanzu apps workload create my-foo \
  --git-repo https://github.com/my-foo/bar \
  --git-branch dev \
  --param dockerfile=./Dockerfile \
  --type web

🔎 Create workload:
      1 + |---
      2 + |apiVersion: carto.run/v1alpha1
      3 + |kind: Workload
      4 + |metadata:
      5 + |  labels:
      6 + |    apps.tanzu.vmware.com/workload-type: web
      7 + |  name: my-foo
      8 + |  namespace: dev
      9 + |spec:
     10 + |  params:
     11 + |  - name: dockerfile
     12 + |    value: ./Dockerfile
     13 + |  source:
     14 + |    git:
     15 + |      ref:
     16 + |        branch: dev
     17 + |      url: https://github.com/my-foo/bar

Similarly, if the context to be used for the build must be set to a different directory within the repository, you can make use of the docker_build_context to change that:

$ tanzu apps workload create my-foo \
  --git-repo https://github.com/my-foo/bar \
  --git-branch dev \
  --param dockerfile=MyDockerfile \
  --param docker_build_context=./src

Important
This feature has no platform operator configurations to be passed through tap-values.yaml, but if ootb-supply-chain-*.registry.ca_cert_data or shared.ca_cert_data is configured in tap-values, the certificates are considered when pushing the container image.

OpenShift

Despite that Kaniko can perform container image builds without needing either a Docker daemon or privileged containers, it does require the use of:

Capabilities usually dropped from the more restrictive SecurityContextConstraints (SCC) enabled by default in OpenShift.
The root user.

To overcome such limitations imposed by the default unprivileged SecurityContextConstraints (SCC), Tanzu Application Platform installs:

SecurityContextConstraints/ootb-templates-kaniko-restricted-v2-with-anyuid with enough extra privileges for Kaniko to operate.
ClusterRole/ootb-templates-kaniko-restricted-v2-with-anyuid to permit the use of such SCC to any actor binding to that cluster role.

Each developer namespace needs a role binding that binds the role to an actor: ServiceAccount. For more information, see Set up developer namespaces to use your installed packages.

apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: workload-kaniko-scc
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: ootb-templates-kaniko-restricted-v2-with-anyuid
subjects:
  - kind: ServiceAccount
    name: default

With the SCC created and the ServiceAccount bound to the role that permits the use of the SCC, OpenShift accepts the pods created to run Kaniko to build the container images.

Note
Such restrictions are due to well-known limitations in how Kaniko performs the image builds, and there is currently no solution. For more information, see kaniko#105.