Most instances on the Nectar Cloud runs Linux (Ubuntu, CentOS). On Nectar’s Linux images, a provisioning tool call cloud-init runs on first boot, which inserts your SSH key and other user data into the instance. This allows you to log in to your instance securely using SSH keys, and also run any scripts for software installation when your instance first boot up.

CoreOS uses a different provisioning tool called Ignition instead of cloud-init. This means that extra steps are necessary to boot up a CoreOS instance and inject your SSH key.

Short way (just SSH key)

  1. If you do not know where your SSH public key is, you can get it from Nectar Dashboard, on the left menu under Project > Compute > Key Pairs. Or you can use the CLI to get it
    openstack keypair show --public-key <NAME>
  2. Create the following file as user-data.json
      "ignition": {
     "version": "3.0.0"
      "passwd": {
     "users": [
         "name": "core",
         "sshAuthorizedKeys": [
           "ssh-rsa AAAAB3NzaC1c2EAA...dzP"
  3. Boot up using CLI
    openstack server boot --image fedora-coreos-31 --flavor m3.small \
    --user-data user_data.json fedora-coreos-instance

Long way

To build an Ignition configuration file, one has to create a YAML config and use the FCOS Configuration Transpiler (FCCT) to convert it into JSON. See Fedora CoreOS pages for more examples.

FCCT is provided as a container, but to run it we need something like podman. This is not installed on Ubuntu by default, so we need to install it.

  1. Create a user-data.yaml like this. In this example we only set an SSH key, but this method is not limited to SSH keys.

     variant: fcos
     version: 1.0.0
         - name: core
             - "ssh-rsa AAAAB3NzaC1c2EAA...dzP"
  2. Install podman by following the Ubuntu instructions on podman’s site.

  3. Run fcct
    podman run -i --rm --pretty \
    --strict < user-data.yaml > user-data.json
  4. You should get the same user-data.json as the previous (short) example.