Extract docker image pipeline

pipeline.yml

resources:
- name: docker-slack-notification
  type: docker-image
  source:
    repository: cfcommunity/slack-notification-resource

- name: my-docker-image-s3
  type: s3
  source:
    access_key_id: ((s3-access-key-id))
    bucket: ((s3-bucket))
    endpoint: ((s3-endpoint))
    secret_access_key: ((s3-secret-access-key))
    regexp: slack-root-fs/rootfs*.tgz
    
jobs:
- name: bump-slack-resource
  serial: true
  plan:
  - get: resource-image
    resource: docker-slack-notification
    params: {rootfs: true}
    trigger: true
  - task: export-rootfs
    config:
      platform: linux
      image_resource:
        type: docker-image
        source:
          repository: concourse/bosh-cli
      inputs:
      - name: custom-res-concourse-boshrelease
      - name: resource-image
      outputs:
      - name: final-rootfs
      run:
        path: sh
        args:
        - -c
        - |
          gzip -c resource-image/rootfs.tar > final-rootfs/rootfs.tgz
  - put: my-docker-image-s3
    params:
      file: "final-rootfs/rootfs*.tgz"