Disk and Container Formats

When adding an image to Glance, you must specify what the virtual machine image’s disk format and container format are. Disk and container formats are configurable on a per-deployment basis. This document intends to establish a global convention for what specific values of disk_format and container_format mean.

Disk Format

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.

You can set your image’s disk format to one of the following:

  • raw

    This is an unstructured disk image format

  • vhd

    This is the VHD disk format, a common disk format used by virtual machine monitors from VMWare, Xen, Microsoft, VirtualBox, and others

  • vmdk

    Another common disk format supported by many common virtual machine monitors

  • vdi

    A disk format supported by VirtualBox virtual machine monitor and the QEMU emulator

  • iso

    An archive format for the data contents of an optical disc (e.g. CDROM).

  • qcow2

    A disk format supported by the QEMU emulator that can expand dynamically and supports Copy on Write

  • aki

    This indicates what is stored in Glance is an Amazon kernel image

  • ari

    This indicates what is stored in Glance is an Amazon ramdisk image

  • ami

    This indicates what is stored in Glance is an Amazon machine image

Container Format

The container format refers to whether the virtual machine image is in a file format that also contains metadata about the actual virtual machine.

Note that the container format string is not currently used by Glance or other OpenStack components, so it is safe to simply specify bare as the container format if you are unsure.

You can set your image’s container format to one of the following:

  • bare

    This indicates there is no container or metadata envelope for the image

  • ovf

    This is the OVF container format

  • aki

    This indicates what is stored in Glance is an Amazon kernel image

  • ari

    This indicates what is stored in Glance is an Amazon ramdisk image

  • ami

    This indicates what is stored in Glance is an Amazon machine image

  • ova

    This indicates what is stored in Glance is an OVA tar archive file

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