glance-specs/specs/api/v1/retrieving_a_virtual_machine_image.rst

Retrieving a Virtual Machine Image

We want to retrieve that actual raw data for a specific virtual machine image that the Glance server knows about.

We have queried the Glance server for a list of public images and the data returned includes the `uri` field for each available image. This `uri` field value contains the exact location needed to get the metadata for a specific image.

Continuing the example from above, in order to get metadata about the first public image returned, we can issue a HEAD request to the Glance server for the image's URI.

We issue a GET request to http://glance.openstack.example.org/images/1 to retrieve metadata for that image as well as the image itself encoded into the response body.

The metadata is returned as a set of HTTP headers that begin with the prefix x-image-meta-. The following shows an example of the HTTP headers returned from the above GET request:

x-image-meta-name             Ubuntu 10.04 Plain 5GB
x-image-meta-disk-format      vhd
x-image-meta-container-format ovf
x-image-meta-size             5368709120
x-image-meta-checksum         c2e5db72bd7fd153f53ede5da5a06de3
x-image-meta-location         swift://account:key/container/image.tar.gz.0
x-image-meta-created_at       2010-02-03 09:34:01
x-image-meta-updated_at       2010-02-03 09:34:01
x-image-meta-deleted_at
x-image-meta-status           available
x-image-meta-is-public        true
x-image-meta-owner            null
x-image-meta-property-distro  Ubuntu 10.04 LTS

All timestamps returned are in UTC

The `x-image-meta-updated_at` timestamp is the timestamp when an
image's metadata was last updated, not its image data, as all
image data is immutable once stored in Glance

There may be multiple headers that begin with the prefix
`x-image-meta-property-`.  These headers are free-form key/value pairs
that have been saved with the image metadata. The key is the string
after `x-image-meta-property-` and the value is the value of the header

The response's `Content-Length` header shall be equal to the value of
the `x-image-meta-size` header

The response's `ETag` header will always be equal to the
`x-image-meta-checksum` value

The response's `x-image-meta-is-public` value is a boolean indicating
whether the image is publicly available

The response's `x-image-meta-owner` value is a string which may either
be null or which will indicate the owner of the image

The image data itself will be the body of the HTTP response returned
from the request, which will have content-type of
`application/octet-stream`.