Images

An Image is a read-only template used to boot a virtual machine. It contains the operating system and optionally pre-installed software. When you launch a VM, OpenStack copies the image to the instance's root disk (ephemeral) or to a boot volume (persistent).

Available Images

OpenStack provides a set of public images with common operating systems. To list them:

openstack image list --public

Available images:

OS Family	Versions	Variants
Ubuntu	22.04, 24.04, 26.04	Standard, LVM, BLK, DevTools, GPU, GPU UEFI, GPU UEFI Cuda
AlmaLinux	9, 10	Standard, LVM
CentOS Stream	9, 10	Standard, LVM
Windows Server	2022, 2025	Standard, Standard Core
Garden Linux	1443, 1592, 1877, 1883, 2150.3	—
CirrOS	0.6.3	—
Grml	2025.12	full (amd64)

Tip

Use openstack image show <image-name> to see details such as disk format, size, and minimum disk requirements.

Boot Source Options

When launching a VM, you choose a Boot Source and whether to create a new volume. This determines which flavor types are compatible:

Boot Source	Create New Volume	Compatible Flavor Types	Comment
Image	Yes	All "Zero-Disk" Flavors (g*) e.g. g1.2c4m, Total Disk = 0	A new boot volume will be created, where you can specify the size (GB).
Image	No	All "Standard" Flavors (e* & m*) e.g. e1.micro, Total Disk = 20 GB	Flavor must have a root disk included (see Flavor list column "Root Disk" > 0 GB).

Tip

Booting from a volume (Create New Volume: Yes) is recommended — the volume persists independently, can be resized, and survives instance deletion.

For the full launch procedure, see Launch Instance.

Create an Image from a Snapshot

You can create an image from an existing volume or a running instance. This is useful for backing up a VM or creating a custom template.

From a volume

openstack image create --volume <volume-name> my-snapshot-image

From a running instance

openstack server image create --name my-snapshot-image <instance-name>

The image appears in Compute > Images and can be used as a boot source for new instances.

Note

Creating an image from a running instance briefly pauses the VM to ensure a consistent disk state.

Custom Images

You can upload your own QCOW2 images to OpenStack. This is useful when you need a pre-configured operating system with custom software installed.

Upload a custom image

openstack image create my-custom-image \
    --disk-format qcow2 \
    --container-format bare \
    --file my-image.qcow2 \
    --public

Image formats

Format	Description
QCOW2	QEMU Copy-On-Write — the recommended format for OpenStack images. Supports snapshots and thin provisioning.
RAW	Uncompressed raw disk image. No overhead but no thin provisioning.
ISO	CD/DVD image — typically used for installation media.

Note

Custom images count against your image quota. Check with openstack quota show.