Task configuration

Task configuration for an virt task includes setting an image to provide the base VM image as well as other parameters required for bootstrapping a VM instance.

• image - (string: required) - Path to an .img cloud image to base the VM disk on. The image should be located in an allowed path. The cloud image needs to include cloud-init, otherwise certain task features are not available. You may also downloaded via the artifact block.

• use_thin_copy - (bool: false) - Make a thin copy of the image using QEMU, and use it as the backing cloud image for the VM.

• hostname - (string: "nomad-<task-name>") - The hostname to assign to the VM. As this value is used as a network host name, it must be a valid DNS label according to RFC 1123. Nomad generates the default value using the Nomad task name.

• cmds - (list(string): optional) - List of commands to execute on the VM once it is running. These commands can provide you with a quick way to start a process on the newly created VM. When used in conjunction with the template, this command list can be a powerful start up tool.

• default_user_password - (string: "") - Initial password for the default user on the newly created VM. When set, the user must update the password on first connect.

• default_user_authorized_ssh_key - (string: "") - SSH public key added to the SSH configuration for the default user of the cloud image distribution.

• user_data - (string: "") - Path to a cloud-init compliant user data file used as the user-data for the cloud-init configuration.

• primary_disk_size - (int: required) - Disk space to assign to the VM. Must fit the VM's OS.

Example:

config {
  image                           = "local/focal-server-cloudimg-amd64.img"
  use_thing_copy                  = false
  hostname                        = ""
  cmds                            = ["python -m http.server 8000"]
  #default_user_password          = "CHANGE-ME"
  default_user_authorized_ssh_key = ""
  user_data                       = ""
  primary_disk_size               = 10000
}

os

The VM architecture and machine can be different from the client host. When this is the case, you must set the os block. By default, this information matches the client host where the driver plugin is running.

• arch - (string: "") - The VM architecture.

• machine - (string: "") - The machine type.

Example:

config {
  os {
    arch    = "x86_64"
    machine = "pc-i440fx-2.9"
  }
}

network_interface

You need to attach tasks to a libvirt network in order to access the internet and route from the local network. The network_interface block enables this as a list of network interfaces that the driver should attach to the VM. This feature only supports a single entry.

• bridge - (block) - Attach the VM to a bridge network. virbr0, the default libvirt network, is a bridge network.

  • name - The name of the bridge interface to use. This relates to the output from commands such as virsh net-info.

  • ports - A list of port labels to expose on the host via mapping to the network interface. These labels must exist within the job specification network block.

Example:

config {
  network_interface {
    bridge {
      name  = "virbr0"
      ports = ["ssh", "http"]
    }
  }
}

Full example

The following job specification displays use of all the configuration options, as well as other blocks that are useful when deploying tasks via the virt driver. You need to modify parameters, such as the default_user_authorized_ssh_key, before use depending on your requirements and Nomad setup.

job "virt-example" {

  group "virt-group" {

    network {
      mode     = "host"
      provider = "nomad"
      port "ssh" {
        to = 22
      }
    }

    task "virt-task" {

      driver = "nomad-driver-virt"

      artifact {
        source      = "http://cloud-images.ubuntu.com/focal/current/focal-server-cloudimg-amd64.img"
        destination = "local/focal-server-cloudimg-amd64.img"
        mode        = "file"
      }

      config {
        image                           = "local/focal-server-cloudimg-amd64.img"
        primary_disk_size               = 26000
        #default_user_password          = "CHANGE-ME"
        default_user_authorized_ssh_key = "ssh-ed25519 AAAAC3NzaC1lZDI..."

        network_interface {
          bridge {
            name  = "virbr0"
            ports = ["ssh"]
          }
        }
      }

      resources {
        cores  = 2
        memory = 4096
      }
    }
  }
}