Glance Overview

Glance is the image management component in OpenStack, it is a simple component in OpenStack and now it is very stable. The purpose of Glance is to store the image template in OpenStack, when we need to create the Virtual Machine (VM) from OpenStack. When you upload the images in Glance, it will upload to a specific location and mark the location, attributes and permissions in database, when we use Nova to create VM, it will check the location and permission then pull down the image from Glance.

Glance Architecture:

Glance has three parts:

-  glance-api: accepts REST-API requests, and working with other two components to fulfill image lookup, upload, delete. By default, it is listening on 9292

-  glance-registry: interact with database to handle the metadata, there are two database tables: image(general image information such as format, image size) and image property (customized image formation)

-  image store: the abstract layer for image storage. Now it supports Amazon S3, Swift, sheepdog, ceph, GlusterFS.

Operations in Glance:

• glance image-create              Create a new image 
• glance image-delete              Delete specified image(s). 
• glance image-download            Download a specific image. 
• glance image-list                List images you can access. 
• glance image-show                Describe a specific image. 
• glance image-update              Update a specific image.