When you add an image to the Image service, you can specify its disk and container formats.

The disk format of a virtual machine image is the format of the underlying disk image. Virtual appliance vendors have different formats for laying out the information contained in a virtual machine disk image. Set the disk format for your image to one of the following values: raw: An unstructured disk image format; if you have a file without an extension it is possibly a raw format. vhd: The VHD disk format, a common disk format used by virtual machine monitors from VMware, Xen, Microsoft, VirtualBox, and others. vmdk: Common disk format supported by many common virtual machine monitors. vdi: Supported by VirtualBox virtual machine monitor and the QEMU emulator. iso: An archive format for the data contents of an optical disc, such as CD-ROM. qcow2: Supported by the QEMU emulator that can expand dynamically and supports Copy on Write. aki: An Amazon kernel image. ari: An Amazon ramdisk image. ami: An Amazon machine image.

The container format indicates whether the virtual machine image is in a file format that also contains metadata about the actual virtual machine. The Image service and other OpenStack projects do not currently support the container format. It is safe to specify bare as the container format if you are unsure. You can set the container format for your image to one of the following values: bare. The image does not have a container or metadata envelope. ovf. The OVF container format. aki. An Amazon kernel image. ari. An Amazon ramdisk image. ami. An Amazon machine image.