This Ruby example starts a virtual machine using the Cloud-Init tool to set the root password and network configuration.

# Find the virtual machine:
vms_service = connection.system_service.vms_service
vm = vms_service.list(search: 'name=myvm')[0]

# Find the service that manages the virtual machine:
vm_service = vms_service.vm_service(vm.id)

# Create a cloud-init script to execute in the
# deployed virtual machine. The script must be correctly
# formatted and indented because it uses YAML.
my_script = "
write_files:
  - content: |
      Hello, world!
    path: /tmp/greeting.txt
    permissions: '0644'
"

# Start the virtual machine, enabling cloud-init and providing the
# password for the root user and the network configuration:
vm_service.start(
  use_cloud_init: true,
  vm: {
    initialization: {
      user_name: 'root',
      root_password: 'redhat123',
      host_name: 'myvm.example.com',
      nic_configurations: [
        {
          name: 'eth0',
          on_boot: true,
          boot_protocol: OvirtSDK4::BootProtocol::STATIC,
          ip: {
            version: OvirtSDK4::IpVersion::V4,
            address: '192.168.0.100',
            netmask: '255.255.255.0',
            gateway: '192.168.0.1'
          }
        }
      ],
      dns_servers: '192.168.0.1 192.168.0.2 192.168.0.3',
      dns_search: 'example.com',
      custom_script: my_script
    }
  }
)

For more information, see http://www.rubydoc.info/gems/ovirt-engine-sdk/OvirtSDK4/VmService:start.