Quick Guide to Getting Started with Glance

Glance is a server that provides the following services:

Ability to store and retrieve virtual machine images
Ability to store and retrieve metadata about these virtual machine images
FUTURE: Convert a virtual machine image from one format to another
FUTURE: Help caching proxies such as Varnish or Squid cache machine images

Communication with Glance occurs via a REST-like HTTP interface.

However, Glance includes a Client <client> class that makes working with Glance easy and straightforward.

In the Cactus release, there will be also command-line tools for interacting with Glance.

Overview of Glance Architecture

There are two main parts to Glance's architecture:

Glance API server
Glance Registry server(s)

Glance API Server

The API server is the main interface for Glance. It routes requests from clients to registries of image metadata and to its backend stores, which are the mechanisms by which Glance actually saves incoming virtual machine images.

The backend stores that Glance can work with are as follows:

Swift

Swift is the highly-available object storage project in OpenStack. More information can be found about Swift here.
Filesystem

The default backend that Glance uses to store virtual machine images is the filesystem backend. This simple backend writes image files to the local filesystem.
S3

This backend allows Glance to store virtual machine images in Amazon's S3 service.
HTTP

Glance can read virtual machine images that are available via HTTP somewhere on the Internet. This store is readonly

Glance Registry Servers

Glance registry servers are servers that conform to the Glance Registry API. Glance ships with a reference implementation of a registry server that complies with this API (bin/glance-registry).

Starting Up Glance's Servers

To get started using Glance, you must first start the Glance API server. After installing Glance, starting up the Glance API server is easy. Simply start the glance-api program, like so:

$> glance-api

Configuring the Glance API server

There are a few options that can be supplied to the API server when starting it up:

verbose

Show more verbose/debugging output
api_host

Address of the host the registry runs on. Defaults to 0.0.0.0.
api_port

Port the registry server listens on. Defaults to 9292.
default_store

The store that the Glance API server will use by default to store images that are added to it. The default value is filesystem, and possible choices are: filesystem, swift, and s3.
filesystem_store_datadir

Directory where the filesystem store can write images to. This directory must be writeable by the user that runs glance-api

Link to docs on the different stores when the documentation on Glance stores is complete.

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