The simplest way to obtain a virtual machine image that works with OpenStack is to download one that someone else has already created.

CirrOS is a minimal Linux distribution that was designed for use as a test image on clouds such as OpenStack Compute. You can download a CirrOS image in various formats from the CirrOS Launchpad download page. If your deployment uses QEMU or KVM, we recommend using the images in qcow2 format. The most recent 64-bit qcow2 image as of this writing is cirros-0.3.0-x86_64-disk.img In a CirrOS image, the login account is cirros. The password is cubswin:)

Canonical maintains an official set of Ubuntu-based images. Images are arranged by Ubuntu release, and by image release date, with "current" being the most recent. For example, the page that contains the most recently built image for Ubuntu 12.04 "Precise Pangolin" is http://cloud-images.ubuntu.com/precise/current/. Scroll to the bottom of the page for links to images that can be downloaded directly. If your deployment uses QEMU or KVM, we recommend using the images in qcow2 format. The most recent version of the 64-bit QCOW2 image for Ubuntu 12.04 is precise-server-cloudimg-amd64-disk1.img. In an Ubuntu cloud image, the login account is ubuntu.

Red Hat maintains an official Red Hat Enterprise Linux 6 cloud image. A valid Red Hat Enterprise Linux 6 subscription is required to download the KVM Guest Image. A boot.iso image is also available. This is the same as the boot.iso file provided on the Red Hat Enterprise Linux installation DVD. It is a minimal image suitable for kickstarting operating system installation over a network.

The Fedora project maintains a list of official cloud images at . The images include the cloud-init utility to support key and user data injection. The default user name is fedora.

SUSE does not provide openSUSE or SUSE Linux Enterprise Server (SLES) images for direct download. Instead, they provide a web-based tool called SUSE Studio that you can use to build openSUSE and SLES images. For example, Christian Berendt used openSUSE to create a test openSUSE 12.1 image.

As of this writing, we are not aware of other distributions that provide images for download.

Rackspace Cloud Builders maintains a list of pre-built images from various distributions (Red Hat, CentOS, Fedora, Ubuntu). Links to these images can be found at rackerjoe/oz-image-build on Github.

Cloudbase Solutions hosts an OpenStack Windows Server 2012 Standard Evaluation image that runs on Hyper-V, KVM, and XenServer/XCP.