Chapter 6. Building of container images using Buildah as a non-root user

Procedure

1. Create a copy of the buildah cluster task as an ordinary task.

   $ oc get clustertask buildah -o yaml | yq '. |= (del .metadata |= with_entries(select(.key == "name" )))' | yq '.kind="Task"' | yq '.metadata.name="buildah-as-user"' | oc create -f -

2. Edit the copied buildah task.

   $ oc edit task buildah-as-user

   Example: Modified Buildah task with build user

   apiVersion: tekton.dev/v1
   kind: Task
   metadata:
     name: buildah-as-user
   spec:
     description: >-
       Buildah task builds source into a container image and
       then pushes it to a container registry.
       Buildah Task builds source into a container image using Project Atomic's
       Buildah build tool.It uses Buildah's support for building from Dockerfiles,
       using its buildah bud command.This command executes the directives in the
       Dockerfile to assemble a container image, then pushes that image to a
       container registry.
     params:
     - name: IMAGE
       description: Reference of the image buildah will produce.
     - name: BUILDER_IMAGE
       description: The location of the buildah builder image.
       default: registry.redhat.io/rhel8/buildah@sha256:99cae35f40c7ec050fed3765b2b27e0b8bbea2aa2da7c16408e2ca13c60ff8ee
     - name: STORAGE_DRIVER
       description: Set buildah storage driver
       default: vfs
     - name: DOCKERFILE
       description: Path to the Dockerfile to build.
       default: ./Dockerfile
     - name: CONTEXT
       description: Path to the directory to use as context.
       default: .
     - name: TLSVERIFY
       description: Verify the TLS on the registry endpoint (for push/pull to a non-TLS registry)
       default: "true"
     - name: FORMAT
       description: The format of the built container, oci or docker
       default: "oci"
     - name: BUILD_EXTRA_ARGS
       description: Extra parameters passed for the build command when building images.
       default: ""
     - description: Extra parameters passed for the push command when pushing images.
       name: PUSH_EXTRA_ARGS
       type: string
       default: ""
     - description: Skip pushing the built image
       name: SKIP_PUSH
       type: string
       default: "false"
     results:
     - description: Digest of the image just built.
       name: IMAGE_DIGEST
       type: string
     workspaces:
     - name: source
     steps:
     - name: build
       securityContext:
         runAsUser: 1000 1
       image: $(params.BUILDER_IMAGE)
       workingDir: $(workspaces.source.path)
       script: |
         echo "Running as USER ID `id`" 2
         buildah --storage-driver=$(params.STORAGE_DRIVER) bud \
           $(params.BUILD_EXTRA_ARGS) --format=$(params.FORMAT) \
           --tls-verify=$(params.TLSVERIFY) --no-cache \
           -f $(params.DOCKERFILE) -t $(params.IMAGE) $(params.CONTEXT)
         [[ "$(params.SKIP_PUSH)" == "true" ]] && echo "Push skipped" && exit 0
         buildah --storage-driver=$(params.STORAGE_DRIVER) push \
           $(params.PUSH_EXTRA_ARGS) --tls-verify=$(params.TLSVERIFY) \
           --digestfile $(workspaces.source.path)/image-digest $(params.IMAGE) \
           docker://$(params.IMAGE)
         cat $(workspaces.source.path)/image-digest | tee /tekton/results/IMAGE_DIGEST
       volumeMounts:
       - name: varlibcontainers
         mountPath: /home/build/.local/share/containers 3
     volumes:
     - name: varlibcontainers
       emptyDir: {}

   1

   Run the container explicitly as the user id 1000, which corresponds to the build user in the Buildah image.

   2

   Display the user id to confirm that the process is running as user id 1000.

   3

   You can change the path for the volume mount as necessary.

Procedure

1. Create a TaskRun object with a custom ConfigMap and Dockerfile objects.

   Example: A task run that runs Buildah as user id 1000

   apiVersion: v1
   data:
     Dockerfile: |
       ARG BASE_IMG=registry.access.redhat.com/ubi9/ubi
       FROM $BASE_IMG AS buildah-runner
       RUN dnf -y update && \
           dnf -y install git && \
           dnf clean all
       CMD git
   kind: ConfigMap
   metadata:
     name: dockerfile 1
   ---
   apiVersion: tekton.dev/v1
   kind: TaskRun
   metadata:
     name: buildah-as-user-1000
   spec:
     taskRunTemplate:
       serviceAccountName: pipelines-sa-userid-1000 2
     params:
     - name: IMAGE
       value: image-registry.openshift-image-registry.svc:5000/test/buildahuser
     taskRef:
       kind: Task
       name: buildah-as-user
     workspaces:
     - configMap:
         name: dockerfile 3
       name: source

   1

   Use a config map because the focus is on the task run, without any prior task that fetches some sources with a Dockerfile.

   2

   The name of the service account that you created.

   3

   Mount a config map as the source workspace for the buildah-as-user task.

2. (Optional) Create a pipeline and a corresponding pipeline run.

   Example: A pipeline and corresponding pipeline run

   apiVersion: tekton.dev/v1
   kind: Pipeline
   metadata:
     name: pipeline-buildah-as-user-1000
   spec:
     params:
     - name: IMAGE
     - name: URL
     workspaces:
     - name: shared-workspace
     - name: sslcertdir
       optional: true
     tasks:
     - name: fetch-repository 1
       taskRef:
         name: git-clone
         kind: ClusterTask
       workspaces:
       - name: output
         workspace: shared-workspace
       params:
       - name: url
         value: $(params.URL)
       - name: subdirectory
         value: ""
       - name: deleteExisting
         value: "true"
     - name: buildah
       taskRef:
         name: buildah-as-user 2
       runAfter:
       - fetch-repository
       workspaces:
       - name: source
         workspace: shared-workspace
       - name: sslcertdir
         workspace: sslcertdir
       params:
       - name: IMAGE
         value: $(params.IMAGE)
   ---
   apiVersion: tekton.dev/v1
   kind: PipelineRun
   metadata:
     name: pipelinerun-buildah-as-user-1000
   spec:
     taskRunSpecs:
       - pipelineTaskName: buildah
         taskServiceAccountName: pipelines-sa-userid-1000 3
     params:
     - name: URL
       value: https://github.com/openshift/pipelines-vote-api
     - name: IMAGE
       value: image-registry.openshift-image-registry.svc:5000/test/buildahuser
     pipelineRef:
       name: pipeline-buildah-as-user-1000
     workspaces:
     - name: shared-workspace 4
       volumeClaimTemplate:
         spec:
           accessModes:
             - ReadWriteOnce
           resources:
             requests:
               storage: 100Mi

   1

   Use the git-clone cluster task to fetch the source containing a Dockerfile and build it using the modified Buildah task.

   2

   Refer to the modified Buildah task.

   3

   Use the service account that you created for the Buildah task.

   4

   Share data between the git-clone task and the modified Buildah task using a persistent volume claim (PVC) created automatically by the controller.

3. Start the task run or the pipeline run.