Implement automatic Glance image updates


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An OpenStack cloud generally benefits from making available the most recent cloud images as it minimizes the need to perform software updates on its VMs. It is also convenient to automate the process of updating these images. This article will show how to accomplish all this with the glance-simplestreams-sync charm.


The glance-simplestreams-sync charm places Simplestreams metadata in Object Storage via the cloud’s swift API endpoint. The cloud will therefore require the presence of either Swift (swift-proxy and swift-storage charms) or the Ceph RADOS Gateway (ceph-radosgw charm).


Deploy the software

Deploy the glance-simplestreams-sync application. Here it is containerised on machine 1:

juju deploy --to lxd:1 glance-simplestreams-sync
juju integrate glance-simplestreams-sync:identity-service keystone:identity-service
juju integrate glance-simplestreams-sync:certificates vault:certificates

We are assuming that the cloud is TLS-enabled (hence the Vault relation).


The glance-simplestreams-sync charm sets up its own image-stream endpoint. However, it is not utilised in this present scenario. It is leveraged when using OpenStack as a backing cloud to Juju.

Configure image downloads

The recommended way to configure image downloads is with a YAML file. As an example, we’ll filter on the following:

  • Focal and Jammy images

  • arm64 and amd64 architectures

  • officially released images and daily images

  • the latest of each found image (i.e. maximum of one)

To satisfy all the above place the below configuration in, say, file ~/gsss.yaml:

  mirror_list: |
    [{ url: '',
       name_prefix: 'ubuntu:released',
       path: 'streams/v1/index.sjson',
       max: 1,
       item_filters: ['arch~(arm64|amd64)', 'ftype~(uefi1.img|uefi.img|disk1.img)', 'release~(focal|jammy)']
     { url: '',
       name_prefix: 'ubuntu:daily',
       path: 'streams/v1/index.sjson',
       max: 1,
       item_filters: ['arch~(arm64|amd64)', 'ftype~(uefi1.img|uefi.img|disk1.img)', 'release~(focal|jammy)']

Now configure the charm by referencing the file:

juju config --file ~/gsss.yaml glance-simplestreams-sync


If a configuration is not provided the applications’s default behaviour is to download the latest official amd64 image for each of the last four LTS releases.

Enable automatic image updates

Enable automatic image updates via the run option. Here we also specify checks to occur on a weekly basis:

juju config glance-simplestreams-sync frequency=weekly run=true

Valid frequencies are ‘hourly’, ‘daily’, and ‘weekly’.

Enabling the run option will trigger an initial update within 60 seconds.

Perform a manual image sync (optional)

A manual image sync can optionally be performed with the sync-images action:

juju run glance-simplestreams-sync/leader sync-images

Sample output:

  UnitId: glance-simplestreams-sync/0
  id: "32"
    Stdout: |
      created 2b0dc3a3-bcac-425b-bbd8-aaa6af848ffd: auto-sync/ubuntu-focal-20.04-amd64-server-20221115.1-disk1.img
      created 1a6964bb-f674-438e-a39f-78b5a274bf19: auto-sync/ubuntu-focal-20.04-arm64-server-20221115.1-disk1.img
      created 1ba8780f-90b1-4872-8b30-8b90be158022: auto-sync/ubuntu-jammy-22.04-amd64-server-20221117-disk1.img
      created 8b9075a3-1528-44d1-8462-7152c7a82a02: auto-sync/ubuntu-jammy-22.04-arm64-server-20221117-disk1.img
      created df861e6a-321e-4025-a8b0-952a2acdf733: auto-sync/ubuntu-focal-daily-amd64-server-20221121-disk1.img
      created cbd91693-cde7-45ab-bbca-0c5d761762d2: auto-sync/ubuntu-focal-daily-arm64-server-20221121-disk1.img
      created e160c75a-b063-45b7-b914-a7669b4244a4: auto-sync/ubuntu-jammy-daily-amd64-server-20221120-disk1.img
      created 92c85d89-2695-48d0-b476-486e9576d931: auto-sync/ubuntu-jammy-daily-arm64-server-20221120-disk1.img
  status: completed
    completed: 2022-11-22 17:58:01 +0000 UTC
    enqueued: 2022-11-22 17:52:15 +0000 UTC
    started: 2022-11-22 17:52:16 +0000 UTC

This output should reflect the information available via the openstack image list command.