Raymii.org

Table of Contents

• Command Line tools
• Openstack Overview
  • Compute (Nova)
  • Block Storage (Cinder)
  • Images (Glance)
• Listing images
• Download Image

This guide shows you how download Openstack Images to your local machine using the command line Glance client. You can use this, for example, to download a copy of an image created from a VM, or to download the images your Openstack provider provides and adapt those.

You can see all my Openstack related articles here. For example, how to use Duplicity to create Encrypted backups to the Openstack Swift Object Store

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Command Line tools

Make sure you have the Openstack command line tools installed. Follow the official openstack guide here. If you have pip installed you can use that to install the tools:

pip install python-novaclient
pip install python-cinderclient
pip install python-glanceclient
pip install python-keystoneclient
pip install python-neutronclient
pip install python-swiftclient

Save yourself some time and create a file named computerc with the below contents:

export OS_AUTH_URL="https://identity.stack.cloudvps.com/v2.0"
export OS_TENANT_NAME="<tenant name>"
export OS_USERNAME="<username>"
export OS_PASSWORD="<password>"
export OS_TENANT_ID="<tenant id>"

When you are going to do stuff with the Openstack command line clients, load this file:

source computerc

That way, your authentication data are loaded and you don't have to give parameters like --os-username and such.

Openstack Overview

Openstack is a datacenter virtualization plaform consisting out of many different tools and services. Here is a short overview of the different services you might encounter.

Compute (Nova)

This is the virtualization service. It works with a hypervisor to create and manage virtual machines. You can create a VM based on a specific "Flavour", which is just a definition of specs like disk, cpu and ram.

Block Storage (Cinder)

This is the service which makes block devices (volumes) available to services. A flavour can not be changed, just resized. If you want extra storage you need to create a volume, attach it to the VM and mount it there for use.

Images (Glance)

This is the service which holds all the images. Images can be used to boot a VM from. Images can be prepared with tools like cloud-init to make them behave better in a cloud environment, for example, setting an SSH key or password at boot.

Listing images

When you've created a computerc file and loaded it up in your shell you can start the process. You need the UUID of the image you want to download. Get a list of all images using the glance image-list command:

$ glance image-list

Output:

+------------+---------------------+--------+-----------+------------+--------+
| ID         | Name                | Disk   | Container | Size       | Status |
+------------+---------------------+--------+-----------+------------+--------+
| 0a[...]5dd | example-test        | raw    | bare      | 4843700224 | active |
| 13[...]b30 | example-2           | qcow2  | bare      | 4762632192 | active |
| 22[...]eeb | FreeBSD-10.1        | qcow2  | bare      | 736981504  | active |
| d2[...]625 | pfSense 2.1.5       | iso    | bare      | 403243008  | active |
+------------+---------------------+--------+-----------+------------+--------+

The ID part is what you need. In this example it is trimmed.

Download Image

Use the glance image-download command to download the image. By default it will go to STDOUT, use the --file parameter to place the output in a file.

$ glance image-download --file ./example-test.img 0a[...]5dd

The command syntax is:

$ glance image-download --file $FILENAME $UUID

If you get the following error:

object of type 'generator' has no len()

Try executing the command without the --progress option.

Tags: cloud , compute , download , glance , image , images , nova , openstack , tutorials