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ReStructuredText
391 lines
14 KiB
ReStructuredText
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Copyright 2010 OpenStack, LLC
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All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License"); you may
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not use this file except in compliance with the License. You may obtain
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a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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License for the specific language governing permissions and limitations
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under the License.
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The Glance REST API
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===================
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Glance has a RESTful API that exposes both metadata about registered virtual
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machine images and the image data itself.
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A host that runs the ``bin/glance-api`` service is said to be a *Glance API
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Server*.
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Assume there is a Glance API server running at the URL
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``http://glance.example.com``.
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Let's walk through how a user might request information from this server.
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Requesting a List of Public VM Images
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-------------------------------------
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We want to see a list of available virtual machine images that the Glance
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server knows about.
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We issue a ``GET`` request to ``http://glance.example.com/images/`` to retrieve
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this list of available *public* images. The data is returned as a JSON-encoded
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mapping in the following format::
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{'images': [
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{'uri': 'http://glance.example.com/images/1',
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'name': 'Ubuntu 10.04 Plain',
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'disk_format': 'vhd',
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'container_format': 'ovf',
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'size': '5368709120'}
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...]}
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.. note::
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All images returned from the above `GET` request are *public* images
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Requesting Detailed Metadata on Public VM Images
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------------------------------------------------
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We want to see more detailed information on available virtual machine images
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that the Glance server knows about.
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We issue a ``GET`` request to ``http://glance.example.com/images/detail`` to
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retrieve this list of available *public* images. The data is returned as a
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JSON-encoded mapping in the following format::
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{'images': [
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{'uri': 'http://glance.example.com/images/1',
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'name': 'Ubuntu 10.04 Plain 5GB',
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'disk_format': 'vhd',
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'container_format': 'ovf',
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'size': '5368709120',
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'checksum': 'c2e5db72bd7fd153f53ede5da5a06de3',
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'location': 'swift://account:key/container/image.tar.gz.0',
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'created_at': '2010-02-03 09:34:01',
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'updated_at': '2010-02-03 09:34:01',
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'deleted_at': '',
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'status': 'active',
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'is_public': True,
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'properties': {'distro': 'Ubuntu 10.04 LTS'}},
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...]}
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.. note::
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All images returned from the above `GET` request are *public* images
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All timestamps returned are in UTC
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The `updated_at` timestamp is the timestamp when an image's metadata
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was last updated, not its image data, as all image data is immutable
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once stored in Glance
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The `properties` field is a mapping of free-form key/value pairs that
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have been saved with the image metadata
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The `checksum` field is an MD5 checksum of the image file data
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Filtering Images Returned via ``GET /images`` and ``GET /images/detail``
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------------------------------------------------------------------------
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Both the ``GET /images`` and ``GET /images/detail`` requests take query
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parameters that serve to filter the returned list of images. The following
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list details these query parameters.
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* ``name=NAME``
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Filters images having a ``name`` attribute matching ``NAME``.
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* ``container_format=FORMAT``
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Filters images having a ``container_format`` attribute matching ``FORMAT``
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For more information, see :doc:`About Disk and Container Formats <formats>`
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* ``disk_format=FORMAT``
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Filters images having a ``disk_format`` attribute matching ``FORMAT``
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For more information, see :doc:`About Disk and Container Formats <formats>`
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* ``status=STATUS``
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Filters images having a ``status`` attribute matching ``STATUS``
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For more information, see :doc:`About Image Statuses <statuses>`
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* ``size_min=BYTES``
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Filters images having a ``size`` attribute greater than or equal to ``BYTES``
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* ``size_max=BYTES``
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Filters images having a ``size`` attribute less than or equal to ``BYTES``
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Requesting Detailed Metadata on a Specific Image
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------------------------------------------------
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We want to see detailed information for a specific virtual machine image
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that the Glance server knows about.
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We have queried the Glance server for a list of public images and the
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data returned includes the `uri` field for each available image. This
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`uri` field value contains the exact location needed to get the metadata
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for a specific image.
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Continuing the example from above, in order to get metadata about the
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first public image returned, we can issue a ``HEAD`` request to the Glance
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server for the image's URI.
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We issue a ``HEAD`` request to ``http://glance.example.com/images/1`` to
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retrieve complete metadata for that image. The metadata is returned as a
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set of HTTP headers that begin with the prefix ``x-image-meta-``. The
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following shows an example of the HTTP headers returned from the above
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``HEAD`` request::
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x-image-meta-uri http://glance.example.com/images/1
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x-image-meta-name Ubuntu 10.04 Plain 5GB
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x-image-meta-disk-format vhd
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x-image-meta-container-format ovf
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x-image-meta-size 5368709120
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x-image-meta-checksum c2e5db72bd7fd153f53ede5da5a06de3
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x-image-meta-location swift://account:key/container/image.tar.gz.0
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x-image-meta-created_at 2010-02-03 09:34:01
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x-image-meta-updated_at 2010-02-03 09:34:01
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x-image-meta-deleted_at
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x-image-meta-status available
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x-image-meta-is-public True
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x-image-meta-property-distro Ubuntu 10.04 LTS
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.. note::
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All timestamps returned are in UTC
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The `x-image-meta-updated_at` timestamp is the timestamp when an
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image's metadata was last updated, not its image data, as all
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image data is immutable once stored in Glance
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There may be multiple headers that begin with the prefix
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`x-image-meta-property-`. These headers are free-form key/value pairs
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that have been saved with the image metadata. The key is the string
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after `x-image-meta-property-` and the value is the value of the header
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The response's `ETag` header will always be equal to the
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`x-image-meta-checksum` value
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Retrieving a Virtual Machine Image
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----------------------------------
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We want to retrieve that actual raw data for a specific virtual machine image
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that the Glance server knows about.
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We have queried the Glance server for a list of public images and the
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data returned includes the `uri` field for each available image. This
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`uri` field value contains the exact location needed to get the metadata
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for a specific image.
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Continuing the example from above, in order to get metadata about the
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first public image returned, we can issue a ``HEAD`` request to the Glance
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server for the image's URI.
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We issue a ``GET`` request to ``http://glance.example.com/images/1`` to
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retrieve metadata for that image as well as the image itself encoded
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into the response body.
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The metadata is returned as a set of HTTP headers that begin with the
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prefix ``x-image-meta-``. The following shows an example of the HTTP headers
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returned from the above ``GET`` request::
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x-image-meta-uri http://glance.example.com/images/1
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x-image-meta-name Ubuntu 10.04 Plain 5GB
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x-image-meta-disk-format vhd
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x-image-meta-container-format ovf
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x-image-meta-size 5368709120
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x-image-meta-checksum c2e5db72bd7fd153f53ede5da5a06de3
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x-image-meta-location swift://account:key/container/image.tar.gz.0
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x-image-meta-created_at 2010-02-03 09:34:01
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x-image-meta-updated_at 2010-02-03 09:34:01
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x-image-meta-deleted_at
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x-image-meta-status available
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x-image-meta-is-public True
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x-image-meta-property-distro Ubuntu 10.04 LTS
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.. note::
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All timestamps returned are in UTC
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The `x-image-meta-updated_at` timestamp is the timestamp when an
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image's metadata was last updated, not its image data, as all
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image data is immutable once stored in Glance
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There may be multiple headers that begin with the prefix
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`x-image-meta-property-`. These headers are free-form key/value pairs
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that have been saved with the image metadata. The key is the string
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after `x-image-meta-property-` and the value is the value of the header
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The response's `Content-Length` header shall be equal to the value of
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the `x-image-meta-size` header
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The response's `ETag` header will always be equal to the
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`x-image-meta-checksum` value
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The image data itself will be the body of the HTTP response returned
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from the request, which will have content-type of
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`application/octet-stream`.
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Adding a New Virtual Machine Image
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----------------------------------
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We have created a new virtual machine image in some way (created a
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"golden image" or snapshotted/backed up an existing image) and we
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wish to do two things:
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* Store the disk image data in Glance
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* Store metadata about this image in Glance
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We can do the above two activities in a single call to the Glance API.
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Assuming, like in the examples above, that a Glance API server is running
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at ``glance.example.com``, we issue a ``POST`` request to add an image to
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Glance::
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POST http://glance.example.com/images/
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The metadata about the image is sent to Glance in HTTP headers. The body
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of the HTTP request to the Glance API will be the MIME-encoded disk
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image data.
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Adding Image Metadata in HTTP Headers
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*************************************
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Glance will view as image metadata any HTTP header that it receives in a
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``POST`` request where the header key is prefixed with the strings
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``x-image-meta-`` and ``x-image-meta-property-``.
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The list of metadata headers that Glance accepts are listed below.
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* ``x-image-meta-name``
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This header is required. Its value should be the name of the image.
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Note that the name of an image *is not unique to a Glance node*. It
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would be an unrealistic expectation of users to know all the unique
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names of all other user's images.
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* ``x-image-meta-id``
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This header is optional.
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When present, Glance will use the supplied identifier for the image.
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If the identifier already exists in that Glance node, then a
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**409 Conflict** will be returned by Glance.
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When this header is *not* present, Glance will generate an identifier
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for the image and return this identifier in the response (see below)
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* ``x-image-meta-store``
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This header is optional. Valid values are one of ``file``, ``s3``, or
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``swift``
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When present, Glance will attempt to store the disk image data in the
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backing store indicated by the value of the header. If the Glance node
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does not support the backing store, Glance will return a **400 Bad Request**.
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When not present, Glance will store the disk image data in the backing
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store that is marked default. See the configuration option ``default_store``
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for more information.
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* ``x-image-meta-disk-format``
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This header is optional. Valid values are one of ``aki``, ``ari``, ``ami``,
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``raw``, ``vhd``, ``vdi``, ``qcow2``, or ``vmdk``.
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For more information, see :doc:`About Disk and Container Formats <formats>`
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* ``x-image-meta-container-format``
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This header is optional. Valid values are one of ``aki``, ``ari``, ``ami``,
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``bare``, or ``ovf``.
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For more information, see :doc:`About Disk and Container Formats <formats>`
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* ``x-image-meta-size``
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This header is optional.
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When present, Glance assumes that the expected size of the request body
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will be the value of this header. If the length in bytes of the request
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body *does not match* the value of this header, Glance will return a
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**400 Bad Request**.
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When not present, Glance will calculate the image's size based on the size
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of the request body.
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* ``x-image-meta-checksum``
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This header is optional. When present it shall be the expected **MD5**
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checksum of the image file data.
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When present, Glance will verify the checksum generated from the backend
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store when storing your image against this value and return a
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**400 Bad Request** if the values do not match.
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* ``x-image-meta-is-public``
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This header is optional.
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When Glance finds the string "true" (case-insensitive), the image is marked as
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a public image, meaning that any user may view its metadata and may read
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the disk image from Glance.
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When not present, the image is assumed to be *not public* and specific to
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a user.
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* ``x-image-meta-property-*``
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When Glance receives any HTTP header whose key begins with the string prefix
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``x-image-meta-property-``, Glance adds the key and value to a set of custom,
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free-form image properties stored with the image. The key is the
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lower-cased string following the prefix ``x-image-meta-property-`` with dashes
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and punctuation replaced with underscores.
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For example, if the following HTTP header were sent::
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x-image-meta-property-distro Ubuntu 10.10
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Then a key/value pair of "distro"/"Ubuntu 10.10" will be stored with the
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image in Glance.
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There is no limit on the number of free-form key/value attributes that can
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be attached to the image. However, keep in mind that the 8K limit on the
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size of all HTTP headers sent in a request will effectively limit the number
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of image properties.
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Updating an Image
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*****************
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Glance will view as image metadata any HTTP header that it receives in a
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``PUT`` request where the header key is prefixed with the strings
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``x-image-meta-`` and ``x-image-meta-property-``.
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If an image was previously reserved, and thus is in the ``queued`` state, then
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image data can be added by including it as the request body. If the image
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already as data associated with it (e.g. not in the ``queued`` state), then
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including a request body will result in a **409 Conflict** exception.
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On success, the ``PUT`` request will return the image metadata encoded as HTTP
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headers.
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See more about image statuses here: :doc:`Image Statuses <statuses>`
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