The Images contain a virtual disk holding a bootable OS (Operating System).
The Instances are the virtuel machines running on physical compute nodes inside the cloud.
You can launch as many instances as you want from the same image, according to available resources.
Some images of standard GNU / Linux systems are provided.
They can be listed with the command openstack image list.
$ openstack image list
+--------------------------------------+----------------------------+--------+
| ID | Name | Status |
+--------------------------------------+----------------------------+--------+
| 11171b45-fedf-4ac1-bd49-8d295bc48a3d | centos-7-x86_64 | active |
| c3eea436-0d16-416e-9484-53b9b46f42e8 | cirros-0.4.0-x86_64 | active |
| bc72fe4c-c0bc-4bd2-8c47-a5235b84ecef | clean-install | active |
| df885582-90d6-419d-a392-8b2575f2b452 | debian-9-x2go-x86_64 | active |
| f54fc509-9db6-4238-87ec-568d4a79968e | debian-9-x86_64 | active |
| b0b2b2b1-ecec-413e-b182-17c530509484 | nixos-18.03-x86_64 | active |
| 827ef987-8681-47ad-9f88-1d80cb90fdbf | rancheros-1.4.2-x86_64 | active |
| c1a459e9-25b7-4fa7-9f95-7ad532b98d06 | ubuntu-16.04-xenial-x86_64 | active |
| 1a8b1650-56cc-43ef-a270-9091c8339d69 | ubuntu-18.04-bionic-x86_64 | active |
| 4b022cbc-0636-4e53-b96e-a09b1f0521c8 | ubuntu-18.10-cosmic-x86_64 | active |
| 43816d62-60c4-4427-be9a-0a79f197657b | ubuntu-xenial-x86_64 | active |
+--------------------------------------+----------------------------+--------+
It is also possible to upload your own image by using openstack image create.
$ openstack image create \
--public \
--disk-format qcow2 \
--container-format bare \
--file /tmp/hurd-sid-i386.img \
hurd-sid-i386.img
To be started directly, the image must be cloud-ready (with cloud-init).