Image Service (Glance)

[yehlu]

The OpenStack Image Service provides discovery, registration and delivery services for disk and server images. The ability to copy or snapshot a server image and immediately store it away is a powerful capability of the OpenStack cloud operating system. Stored images can be used as a template to get new servers up and running quickly—and more consistently if you are provisioning multiple servers—than installing a server operating system and individually configuring additional services. It can also be used to store and catalog an umlimited number of backups.

The Image Service can store disk and server images in a variety of back-ends, including OpenStack Object Storage. The Image Service API provides a standard REST interface for querying information about disk images and lets clients stream the images to new servers.

Capabilities of the Image Service include:

Administrators can create base templates from which their users can start new compute instances
Users can choose from available images, or create their own from existing servers
Snapshots can also be stored in the Image Service so that virtual machines can be backed up quickly

A multi-format image registry, the image service allows uploads of private and public images in a variety of formats, including:

Raw
Machine (kernel/ramdisk outside of image, a.k.a. AMI)
VHD (Hyper-V)
VDI (VirtualBox)
qcow2 (Qemu/KVM)
VMDK (VMWare)
OVF (VMWare, others)