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Using Light Stemcells


This feature is available with bosh-openstack-cpi v28+.


This feature is available with bosh-cli v2.0.40+.

You can create your own OpenStack light stemcells to re-use stemcell images already uploaded to your OpenStack image store.

Note: Future deployments will fail if the stemcell image referenced by a light stemcell is removed from your OpenStack image store.

  1. Download the heavy stemcell for which you want to create a light stemcell
  2. Upload the stemcell to your OpenStack with bosh upload-stemcell and retrieve the CID and version with bosh stemcells. In case this is not possible, please read the example Manually upload stemcell with OpenStack CLI
  3. Use bosh repack-stemcell to create a light stemcell archive from a heavy stemcell
    bosh repack-stemcell --version "<Stemcell version>" \
    --empty-image \
    --format openstack-light \
    --cloud-properties="{\"image_id\": \"<Stemcell CID>\"}" \
    heavy-stemcell.tgz ./light-bosh-stemcell-<Stemcell version>-openstack-kvm-ubuntu-xenial-go_agent.tgz

You can use the light stemcell archive like a regular stemcell archive in BOSH deployment manifests and with bosh create-env command.

Example: Manually upload stemcell with OpenStack CLI

Untar the downloaded heavy stemcell and its image to extract the root.img

tar -xvf bosh-stemcell-170.12-openstack-kvm-ubuntu-xenial-go_agent.tgz
cd bosh-stemcell-170.12-openstack-kvm-ubuntu-xenial-go_agent
tar -xvf image

Upload the root.img to the OpenStack project

openstack image create \
  --container-format bare \
  --disk-format qcow2 \
  --file root.img \
  --property architecture=x86_64 \
  --property auto_disk_config=true \
  --property hypervisor_type=kvm \
  --property os_distro=ubuntu \
  --property os_type=linux \
  --property version=170.12 \

Note: The stemcell.MF can be referred to for setting the properties. In case a stemcell has already been uploaded, openstack image show <Image ID> may also provide helpful information.

For repacking the heavy stemcell into a light stemcell, the <Stemcell CID> can be retrieved from the output of the command above.