Operating System Images

Operating System images are managed by the OpenStack Glance service. The
openstack image command is part of the OpenStack Client (OSC) and allows
users to interact with images within an OpenStack cloud. This documentation
covers how to list available images, find specific images, and upload new
images using the openstack command.

Prerequisites

Before using the openstack command, ensure that the OpenStack Client is
installed and properly configured. You should have sourced your OpenStack RC
file or configured your clouds.yaml to set the necessary environment
variables for authentication.

Listing Images

To view all the available images within your OpenStack project, use the following command:

openstack image list

This command returns a list of images, including details such as the image ID,
name, status, and visibility.

Example Output

+--------------------------------------+------------------+--------+
| ID                                   | Name             | Status |
+--------------------------------------+------------------+--------+
| 9b6d68e8-4c4a-4f5d-a4c1-bc43e0e4c123 | Ubuntu 24.04 LTS | active |
| 3f7c7b28-5c57-483a-9f29-ec041c798765 | CentOS 9         | active |
+--------------------------------------+------------------+--------+

Finding a Specific Image

To find a specific image by its name, you can use the openstack image list command
with the --name filter:

openstack image list --name <image_name>

Replace with the name of the image you want to find. For example, to
find an image named "Ubuntu 24.04 LTS":

openstack image list --name "Ubuntu 20.04 LTS"

You can filter the list by using the --property key=value or --tag tag
arguments as well.

openstack image list --property os_distro=ubuntu

Adding an Image

You can upload your own image to provision onto systems assuming they are
whole disk images. You must know some metadata about the image you are
uploading and no verification of the metadata will be performed. For
example to upload an image based on Ubuntu 24.04 you could run:

openstack image create 'My-Ubuntu-24.04' \
  --disk-format qcow2 \
  --property os_distro=ubuntu \
  --property os_version=24.04 \
  --progress \
  --file=/path/to/image.qcow2

Explanation:

• --disk-format qcow2: Specifies the disk format of the image (e.g., qcow2, raw, vmdk).
• --file /path/to/image.qcow2: Specifies the path to the image file on your local machine.
• --public: (Optional) Makes the image publicly accessible. Remove this flag to keep the image private to your project.

Image Properties

Every image uploaded to Glance should have a set of metadata properties applied
to it. OpenStack does not enforce required properties on images, but our
environment relies on these properties for filtering, automation, and
consistent catalog presentation. Treat the following properties as required
when creating or importing any image.

Property	Description
os_distro	Short identifier for the OS distribution (lowercase, no spaces).
os_version	Version string of the OS (e.g. 24.04, 9.1.0, 2025).
os_type	Kernel type of the operating system. See important note below.
os_name	Human-readable display name for the OS.

Important

os_type only accepts linux or windows as values. There are
no other valid options. Even non-Linux unix-like systems (e.g. ESXi) should
use linux.

Setting Properties

Properties can be set at image creation time with --property flags:

openstack image create 'My-Ubuntu-24.04' \
  --disk-format qcow2 \
  --property os_distro='ubuntu' \
  --property os_version='24.04' \
  --property os_type='linux' \
  --property os_name='Ubuntu' \
  --progress \
  --file=/path/to/image.qcow2

Or applied to an existing image using openstack image set:

openstack image set \
    --property os_distro='ubuntu' \
    --property os_version='24.04' \
    --property os_type='linux' \
    --property os_name='Ubuntu' \
    <image-id>

Known Property Values

To prevent fragmentation, use the values from the tables below. If you need to
add a new OS that is not listed here, coordinate with the team so the table can
be updated.

os_distro

Value	OS
almalinux	Alma Linux
cirros	Cirros
esxi	VMware ESXi
flatcar	Flatcar Container Linux
talos	Talos Linux
ubuntu	Ubuntu
windows	Microsoft Windows

os_type

Value	Description
linux	All Linux and unix-like operating systems (including ESXi)
windows	Microsoft Windows operating systems

os_name

Value	When to use
Alma Linux	Alma Linux images
Cirros	Cirros test images
ESXi	VMware ESXi images
Flatcar Container Linux	Flatcar Container Linux images
Talos	Talos Linux images
Ubuntu	Ubuntu images
Windows Server	Windows Server images

Additional Information

For more detailed information on the openstack image command and its various
options, refer to the official OpenStack documentation:

• OpenStack CLI Command Reference - Image
• OpenStack Image Service (Glance) Documentation

Talos Linux

You can use Talos Linux in Understack.

Using the Talos image factory to create the image:

• Under Hardware Type choose Cloud Server and hit next
• Choose the version and hit next
• Choose OpenStack for the Cloud provider and hit next
• Choose your machine architecture - in our case it's amd64 - and hit next
• Choose system extensions and drivers you may need. In our case we want the amd-ucode extension. Then hit next.
• Choose any customizations you may need. Understack works with the defaults. Then hit next.
• On this page you can download The disk image for example openstack-amd64.raw.xz

We can now take the raw image and add it to glance to make it available for new server builds:

openstack image create --public --disk-format raw --file openstack-amd64.raw 'Talos 1.10.0'

Ensure the image has config drive as mandatory:

openstack image set --property img_config_drive='mandatory' $NEW_IMAGE_UUID

VMware ESXi

The VMware ESXi installer can be made into an image that can be booted on a machine.
It will not work directly but instead must be converted using the esxi-img
utility. To start you will need the VMware ESXi ISO from VMware.

Tip

You can store the ISO in glance so that you don't have to find it on VMware's
website again.

openstack image create \
  --container-format bare \
  --disk-format raw \
  --private \
  --file ~/Downloads/VMware-VMvisor-Installer-8.0U3-24022510.x86_64.iso \
  'ESXi 8.0u3 ISO'

Then you can fetch it later.

openstack image save --file esxi-80u3.iso 'ESXi 8.0u3 ISO'

If you have uv installed then you can use uvx to
run it. The following will produce a converted image that can be uploaded to
glance and booted.

uvx esxi-img gen-img esxi-80u3.iso esxi-80u3.raw

To upload it to glance run the following:

openstack image create \
  --container-format bare \
  --disk-format raw \
  --public \
  --file esxi-80u3.raw \
  --property img_config_drive=mandatory \
  'ESXi 8.0u3'