Image metadata

Image metadata

Image metadata can help end users determine the nature of an image, and is used by associated OpenStack components and drivers which interface with the Image service.

Metadata can also determine the scheduling of hosts. If the property option is set on an image, and Compute is configured so that the ImagePropertiesFilter scheduler filter is enabled (default), then the scheduler only considers compute hosts that satisfy that property.

Note

Compute’s ImagePropertiesFilter value is specified in the enabled_filters value in the [filter_scheduler] section of the /etc/nova/nova.conf file.

You can add metadata to Image service images by using the --property key=value parameter with the openstack image create or openstack image set command. More than one property can be specified. For example:

$ openstack image set --property architecture=arm \
  --property hypervisor_type=qemu image_name_or_id

Common image properties are also specified in the /etc/glance/schema-image.json file. For a complete list of valid property keys and values, refer to the OpenStack Command-Line Reference.

All associated properties for an image can be displayed using the openstack image show command. For example:

$ openstack image show cirros
+------------------+------------------------------------------------------+
| Field            | Value                                                |
+------------------+------------------------------------------------------+
| checksum         | ee1eca47dc88f4879d8a229cc70a07c6                     |
| container_format | bare                                                 |
| created_at       | 2016-04-15T13:57:38Z                                 |
| disk_format      | qcow2                                                |
| file             | /v2/images/55f0907f-70a5-4376-a346-432e4ec509ed/file |
| id               | 55f0907f-70a5-4376-a346-432e4ec509ed                 |
| min_disk         | 0                                                    |
| min_ram          | 0                                                    |
| name             | cirros                                               |
| owner            | f9574e69042645d6b5539035cb8c00bf                     |
| properties       | architecture='arm', hypervisor_type='qemu'           |
| protected        | False                                                |
| schema           | /v2/schemas/image                                    |
| size             | 13287936                                             |
| status           | active                                               |
| tags             |                                                      |
| updated_at       | 2016-04-15T13:57:57Z                                 |
| virtual_size     | None                                                 |
| visibility       | public                                               |
+------------------+------------------------------------------------------+

Note

Volume-from-Image properties

When creating Block Storage volumes from images, also consider your configured image properties. If you alter the core image properties, you should also update your Block Storage configuration. Amend glance_core_properties in the /etc/cinder/cinder.conf file on all controller nodes to match the core properties you have set in the Image service.

Metadata definition service

With this service you can define:

Namespace
  • Contains metadata definitions.
  • Specifies the access controls for everything defined in the namespace. These access controls determine who can define and use the definitions in the namespace.
  • Associates the definitions with different types of resources.
Property
A single property and its primitive constraints. Each property can only be a primitive type. For example, string, integer, number, boolean, or array.
Object

Describes a group of one to many properties and their primitive constraints. Each property in the group can only be a primitive type. For example, string, integer, number, boolean, or array.

The object may optionally define required properties under the semantic understanding that if you use the object, you should provide all required properties.

Resource type association
Specifies the relationship between resource types and the namespaces that are applicable to them. This information can be used to drive UI and CLI views. For example, the same namespace of objects, properties, and tags may be used for images, snapshots, volumes, and flavors. Or a namespace may only apply to images.

The Image service has predefined namespaces for the metadata definitions catalog. To load files from this directory into the database:

$ glance-manage db_load_metadefs

To unload the files from the database:

$ glance-manage db_unload_metadefs

To export the definitions in JSON format:

$ glance-manage db_export_metadefs

Note

By default, files are loaded from and exported to the Image service’s /etc/glance/metadefs directory.

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