Petitboot boot driver

This adds petitboot boot driver for OpenPOWER servers. The OpenPOWER Foundation is a collaboration around Power Architecture products initiated by IBM.

Problem description

OpenPOWER servers use FSP (flexible service processor) to initialize the system chip and monitor the other hardware components. FSP can be set to OPAL (Open Power Abstract Layer) mode to handle the IPMI operation. The firmware on OpenPOWER servers use petitboot as a platform independent bootloader. Petitboot can load kernel, initrd and device tree files from any Linux mountable filesystem, plus can load files from the network using the FTP, SFTP, TFTP, NFS, HTTP and HTTPS protocols.

Petitboot is very similar to the standard pxe behaviour, but a little difference, like:

  • Petitboot will be loaded every time no matter what the boot device is.
  • Petitboot will check the system configuration like boot device in the firmware and will not download any netboot loader, as itself can be worked as a netboot loader.
  • If boot device is hard disk, petitboot will scan boot or prep partition to load the boot option from the local boot loader, for example grub2, then let grub2 load the system.
  • If boot device is network, petitboot will look for PXE configuration file (209) option in the dhcp response. If no explicit configuration file is given, then petitboot will attempt pxelinux-style configuration auto-discovery, using the machine’s MAC address, the IP of the DHCP lease, and fall back to a file named default.
  • Petitboot requests images from network according to the path information in the configuration file, then use kexec to load the system. So both the deploy system and the instance system should support boot from kexec when the boot device is network.
  • The format of petitboot configuration file for netboot is different from the pxelinux.cfg and more kernel command parameters about network should be passed.

Proposed change

  • Add iscsi_opc and agent_opc drivers. opc means OpenPOWER controller which use petitboot driver as the boot driver and ipminative driver as the hardware control driver. For example, the iscsi_opc driver will look like this

    class OpenPOWERIscsiAndIPMINativeDriver(base.BaseDriver):
    """Petitboot + Iscsi + IPMINative driver"""
      def __init__(self):
        self.power = ipminative.NativeIPMIPower()
        self.console = ipminative.NativeIPMIShellinaboxConsole()
        self.boot = petitboot.PetitbootBoot()
        self.deploy = iscsi_deploy.ISCSIDeploy() = ipminative.NativeIPMIManagement()
        self.vendor = iscsi_deploy.VendorPassthru()
        self.inspect = inspector.Inspector.create_if_enabled(
  • Add configuration option for petitboot driver in ironic.conf

    config_template: template path for petitboot configuration.
    protocol: string value for the transfer protocol, only support http and
              tftp in this spec, default http.
  • Add Petitboot driver inherits base.BootInterface and implements the following functions.

    • validate() - Check boot option and image type. In this spec, OpenPOWER machine only support local boot with whole disk image and netboot with partition images.

    • get_properties - In this spec, return common properties which are as same as the properties of pxe driver.

    • prepare_ramdisk() - Petitboot driver will update the dhcp option, build the configuration file for the petitboot netboot loader, then set the boot device to network. This procedure is similar to the pxe driver, but a little difference.

      • Petitboot do not need NBP file, so petitboot driver will not pass bootfile-name (67) option to dhcp. Petitboot driver will use PXE configuration file (209) option and PXE path prefix (210) option to locate the configuration file. Petitboot will concatenate these values to generate the file transfer request. The value of 209 option is the relative file path like <node_uuid>/config. The value of 210 option depends on the protocol configuration in the petitboot section.

        • If it is tftp, the value of 210 option is CONF.deploy.tftp_root
        • If it is http, the value of 210 option is CONF.deploy.http_url.
      • Petitboot driver will manage this configuration file which contains the path information for the kernel and ramdisk. The format of the configuration file is like

        default deploy
        label deploy
        kernel ``{{ [petitboot_url]/<node_uuid>/deploy_kernel }}``
        initrd ``{{ [petitboot_url]/<node_uuid>/deploy_ramdisk }}``
        append ``{{ parameter }}``
    • clean_up_ramdisk() - Cleans up the environment that was setup for booting the deploy system. It unlinks the deploy kernel/ramdisk.

    • prepare_instance() - This method is very similar to the pxe driver.

      • If boot option is local, just clean up the petitboot configuration file.
      • If boot option is network, update the petitboot configuration file to boot the instance image.
    • clean_up_instance() - Cleans up the environment that was setup for booting the instance. It unlinks the instance kernel/ramdisk and removes the petitboot config.



Data model impact


RPC API impact


State Machine Impact


REST API impact


Client (CLI) impact


Driver API impact


Nova driver impact


Ramdisk impact

A ramdisk capable of running on PPC64 hardware will need to be built, however, this may be done downstream.

Support should be added to ramdisk build tooling, such as disk-image-builder and coreos-image-builder, to build such ramdisks.

Security impact


Other end user impact

To use petitboot driver for the OpenPOWER servers, the cpu_arch in driver properties should be ppc64le or ppc64 which depends on the cpu architecture of instance image. OpenPOWER servers can switch to the appropriate endian format according to the endian format of kernel image. Both the deploy kernel and the instance kernel should support boot from kexec when local boot is not enabled.

Scalability impact


Performance Impact


Other deployer impact

New config options

config_template: template path for petitboot configuration.
protocol: string value for the transfer protocol, only support http
          and tftp in this spec, default http.

Developer impact




Primary assignee:
chenglch <>
Other contributors:
baiyuan <>

Work Items

  • Implement petitboot boot driver.
  • Add iscsi_opc and agent_opc drivers to manage the OpenPOWER servers.
  • Write unit-test cases.
  • Write configuration documents.




  • Unit Tests
  • Third-party CI Tests: We have plan to build 3rd-party CI for this driver, but do not have sufficient hardware available at this time.

Upgrades and Backwards Compatibility

This driver will not break any compatibility with either on REST API or RPC APIs.

Documentation Impact

Writing documents to instruct operators how to use Ironic with petitboot driver.