Cloud image metadata


When Juju creates a controller it needs two critical pieces of information:

  1. The UUID of the image to use when spawning a new machine (instance).
  2. The URL from which to download the correct Juju agent.

This "metadata" is stored in a JSON format called Simplestreams. It is built-in for most clouds Juju is aware of but needs to be configured if you're setting up your own cloud.

There are a few ways to do this based on the design of the OpenStack cloud and your level of permissions with Juju and the OpenStack deployment:


  • python-openstackclient
  • python-swiftclient

Generating the metadata

To begin, create a directory to hold the generated metadata:

mkdir -p ~/simplestreams/images

Now, if necessary, source the nova.rc file for your cloud:

. ~/nova.rc

We can now determine the region name for the cloud by running:

openstack endpoint list

The output from the above command will be similar to the following:

| ID                               | Region    | Service Name | Service Type |
| 3cd5449e46c2427985c2ee4810241066 | RegionOne | nova         | compute      |
| 893e4cb67060462d9f2049f0be709587 | RegionOne | keystone     | identity     |
| 14c35ba5b03d44f48724ff53b4762136 | RegionOne | neutron      | network      |
| b3808463bcdd488a800c6025cb8b7bcc | RegionOne | glance       | image        |
| d16a01e7abca4b0c9124c3f13beec5af | RegionOne | swift        | object-store |

Make a note of the region name (RegionOne in the above example). This will be required in a later step.

Next, enter the following command to determine the Image ID of the cloud image in glance:

openstack image list -f value

The following example output shows two images listed, Ubuntu 16.04 (Xenial) and Ubuntu 14.04 (Trusty).

e9df831d-9632-4e06-bd21-d047e4c5ef4e xenial active
6911e505-3610-4f42-b339-994cfe373174 trusty active

Take a note of the image IDs for the images you want added to Simplestreams. These will be used in the next step.

Note: If you have images for multiple different series of Ubuntu, make sure you keep track of which series name matches which image ID. The value $IMAGE_ID, used below, will apply to the image ID of the image for the particular series you are specifying and $OS_SERIES will be the series name ("trusty", "xenial", etc.).

We can now use Juju to generate the metadata:

juju metadata generate-image -d ~/simplestreams -i $IMAGE_ID -s $OS_SERIES -r $REGION -u http://$KEYSTONE_IP:5000/v2.0/

Replace these values with your own in the above command:

  • $IMAGE_ID - The image ID we are creating metadata for.
  • $OS_SERIES - The appropriate series this image relates to (e.g. Xenial).
  • $REGION - The region name of the cloud.
  • $KEYSTONE_IP - The address of the cloud's keystone server.

Note: You can also specify, via the --stream option, an image stream (see [Image streams][anchor__image-streams]) that is not 'released' (i.e. 'daily'). However, doing so will require you to specify this stream explicitly when using this metadata to create any subsequent controllers.

If you have images for multiple series of Ubuntu, run this command again for each series substituting $OS_SERIES with the series name and $IMAGE_ID with the image ID that matches that series.

To verify that the correct metadata files have been generated, you may run:

ls ~/simplestreams/*/streams/*

You should see .json files containing the details we just added on the images.

Use of a local directory for image metadata

Stop here and return to the bootstrap instructions.

Upload the Simplestreams Metadata to Swift

Enter the following command to create a new container for the Simplestreams metadata:

openstack container create simplestreams

You can verify the container has been created by running:

openstack container list

Enter the following command to view the status of the container:

openstack container show simplestreams

Output will look similar to the following:

| Field        | Value         |
| account      | v1            |
| bytes_used   | 0             |
| container    | simplestreams |
| object_count | 0             |

Notice the objects_count line. You should see that the container does not contain any objects.

To upload the Simplestreams metadata to the container, enter the following:

cd ~/simplestreams
swift upload simplestreams *

The output to the previous command will list the json files imported into Swift. Now check the status of the container:

swift stat simplestreams

This will produce output similar to the following:

                      Account: v1
                    Container: simplestreams
                      Objects: 3
                        Bytes: 14261
                     Read ACL:
                    Write ACL:
                      Sync To:
                     Sync Key:
                Accept-Ranges: bytes
             X-Storage-Policy: default-placement
X-Container-Bytes-Used-Actual: 20480
                  X-Timestamp: 1484915544.60265
                   X-Trans-Id: tx00000000000000000000b-0058820665-1084-default
                 Content-Type: text/plain; charset=utf-8

Notice the Objects: line is showing multiple objects after uploading the Simplestreams metadata.

Currently, there are no values for Read or Write ACLs, making this essentially a private container. Enter the following command to add a Read ACL that will make the container publicly accessible:

swift post simplestreams --read-acl .r:*

If you run the swift stat simplestreams command again, you will now see .r:* adjacent to the 'Read ACL' field.

Create a Simplestream service

Enter the following command to create a new service in the Keystone service catalog for Simplestreams:

openstack service create --name product-stream --description "Product Simple Stream" product-streams

Next, enter the following command to determine the URL in Swift for the Simplestreams objects:

openstack endpoint show object-store

The output from the previous command will be similar to the following:

| Field        | Value                            |
| adminurl     |       |
| enabled      | True                             |
| id           | d16a01e7abca4b0c9124c3f13beec5af |
| internalurl  |    |
| publicurl    |    |
| region       | RegionOne                        |
| service_id   | d4dff1dd2e4540f18714703379ea5015 |
| service_name | swift                            |
| service_type | object-store                     |

The URL for the Object Store is listed against the internalurl field above and we refer to this as $SWIFT_URL in the following commands.

Enter the following command to register the endpoint with the Simplestreams service, when using Identity v3:

openstack endpoint create --region $REGION product-streams public $SWIFT_URL/simplestreams/images
openstack endpoint create --region $REGION product-streams internal $SWIFT_URL/simplestreams/images

Using Identity v2:

openstack endpoint create --region $REGION --publicurl $SWIFT_URL/simplestreams/images \
   --internalurl $SWIFT_URL/simplestreams/images product-streams

Bootstrap with Juju

Now the Simplestream service is registered and running you can create a controller on this cloud with the juju bootstrap command.

juju bootstrap <cloud> <controller name> --config image-metadata-url=$SWIFT_URL

If there are multiple possible networks available to the cloud, it is also necessary to specify the network label or UUID for Juju to use. Both the network label and UUID can be retrieved with the following command:

openstack network list

Finally, use either the network label or the UUID with the 'network' configuration option when bootstrapping a new controller:

juju bootstrap openstack --config image-metadata-url=$SWIFT_URL --config network=<network id>

Note: An image stream will need to be explicitly stated, via the 'image-stream' model config option, if a non-default image stream was chosen during the metadata-creation step above.

See Creating a controller for details on creating a controller.

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