#Building Images Using OCI Connector in K8S Job

Before reading, please refer to The General Logic of Using the OCI Connector Proxy in K8S Workload

#Feature Overview

This article will guide you on how to use the OCI Connector to build images within a Kubernetes Job and push them to a Registry. With the capabilities of the OCI Connector, ordinary users can operate without needing to touch or configure authentication credentials, thereby maximizing the security of these credentials.

When using the OCI Connector within a Kubernetes Job, the following key points should be noted:

• Change the address of the target image being built to the connector's proxy address. What is the Connector Proxy Address
  • For example: harbor.example.cn/test/abc
    -> harbor.default.cluster.local/test/abc
• Mount the configuration provided by the Connector.
• Configure insecure registry for the client tools.

This article will take buildkitd as an example and detail the process of creating a Kubernetes Job to complete the image building and pushing utilizing the OCI Connector, without the need to configure authentication information on the client side.

#Prerequisites

• Create a Connector.
• A Dockerfile for building the image.

#Connector

kubectl apply -f - <<EOF
apiVersion: connectors.alauda.io/v1alpha1
kind: Connector
metadata:
  name: harbor
spec:
  address: https://harbor.example.com # Replace with an accessible OCI registry address
  auth:
    name: tokenAuth
    params:
    - name: repository
      value: testing/busybox
    secretRef:
      name: harbor-secret
  connectorClassName: oci
---
apiVersion: v1
stringData: # Replace with actual authentication information
  password: admin
  username: admin
kind: Secret
metadata:
  name: harbor-secret
type: cpaas.io/distribution-registry-token
EOF

#Dockerfile

To demonstrate the building and pushing process, we need to prepare a Dockerfile. To simplify the operation, we will store the content of the Dockerfile in a ConfigMap and mount it to the Pod using a Kubernetes Pod volume.

kubectl apply -f - <<EOF
apiVersion: v1
kind: ConfigMap
metadata:
  name: dockerfile
data:
  Dockerfile: |
    FROM scratch
    LABEL maintainer="example@example.com"
    WORKDIR /app
    ENV APP_VERSION="1.0.0"
EOF

#Operational Steps

#Creating the K8S Job

• To utilize the connector's proxy capabilities, we need to inject the authentication information required by the proxy into docker/config.json. A volume must be provided to mount docker/config.json.
• To allow the client to access the HTTP proxy, we need to configure insecure-registries for the client. A volume must be provided to mount buildkitd.toml.
• Modify the address of the pushed image to the connector's proxy address.

For information on obtaining the Connector's proxy address, see: OCI Connector Class Proxy Information Description

The Job content is as follows:

cat << EOF | kubectl create -f -
kind: Pod
apiVersion: v1
metadata:
  generateName: buildkit-build-
spec:
  restartPolicy: Never
  containers:
  - name: buildkit
    image: docker-mirrors.alauda.cn/moby/buildkit:v0.18.2
    securityContext:
      privileged: true
    env:
    - name: BUILDKITD_FLAGS
      value: "--config /etc/buildkit/buildkitd.toml"
    command:
    - /bin/sh
    - -c
    args:
    - |
      set -ex
      buildctl-daemonless.sh --debug \
      build \
      --progress=plain \
      --frontend=dockerfile.v0 \
      --opt filename=Dockerfile \
      --local context=/workspace \
      --local dockerfile=/workspace \
      --output type=image,name=c-harbor.default.svc.cluster.local/test/test-cjt:v1,push=true \
      --export-cache type=inline
    volumeMounts:
    - name: dockerfile
      mountPath: /workspace
    - name: docker-config
      mountPath: /root/.docker
    - name: buildkitd-config
      mountPath: /etc/buildkit

  volumes:

  # Mounting the dockerfile to the Pod
  - name: dockerfile
    configMap:
      name: dockerfile

  # Mounting docker's config.json to the Pod
  - name: docker-config
    csi:
      readOnly: true
      driver: connectors-csi
      volumeAttributes:
        connector.name: "harbor"
        configuration.names: "docker-config"

  # Mounting buildkitd.toml to the Pod
  - name: buildkitd-config
    csi:
      readOnly: true
      driver: connectors-csi
      volumeAttributes:
        connector.name: "harbor"
        configuration.names: "buildkitd"
EOF

#Operational Results

You can check whether the Job has executed successfully with the following command:

$ kubectl get job

#Summary

We have completed the entire process of "Building Images Using OCI Connector in K8S Job." We can observe that during the execution of the Job, users are required to specify the authentication information for the image repository, and within the Pod running the Job, users cannot access the authentication data configured for the Connector. This greatly ensures that credentials are not leaked in practical usage, safeguarding the security of the tool's authentication information.