Advanced features

Advanced features

Local boot with partition images

The Bare Metal service supports local boot with partition images, meaning that after the deployment the node’s subsequent reboots won’t happen via PXE or Virtual Media. Instead, it will boot from a local boot loader installed on the disk.


Whole disk images, on the contrary, support only local boot, and use it by default.

It’s important to note that in order for this to work the image being deployed with Bare Metal service must contain grub2 installed within it.

Enabling the local boot is different when Bare Metal service is used with Compute service and without it. The following sections will describe both methods.

Enabling local boot with Compute service

To enable local boot we need to set a capability on the bare metal node, for example:

openstack baremetal node set <node-uuid> --property capabilities="boot_option:local"

Nodes having boot_option set to local may be requested by adding an extra_spec to the Compute service flavor, for example:

nova flavor-key baremetal set capabilities:boot_option="local"


If the node is configured to use UEFI, Bare Metal service will create an EFI partition on the disk and switch the partition table format to gpt. The EFI partition will be used later by the boot loader (which is installed from the deploy ramdisk).

Enabling local boot without Compute

Since adding capabilities to the node’s properties is only used by the nova scheduler to perform more advanced scheduling of instances, we need a way to enable local boot when Compute is not present. To do that we can simply specify the capability via the instance_info attribute of the node, for example:

openstack baremetal node set <node-uuid> --instance-info capabilities='{"boot_option": "local"}'

Specifying the disk for deployment (root device hints)

The Bare Metal service supports passing hints to the deploy ramdisk about which disk it should pick for the deployment. The list of supported hints is:

  • model (STRING): device identifier

  • vendor (STRING): device vendor

  • serial (STRING): disk serial number

  • size (INT): size of the device in GiB


    A node’s ‘local_gb’ property is often set to a value 1 GiB less than the actual disk size to account for partitioning (this is how DevStack, TripleO and Ironic Inspector work, to name a few). However, in this case size should be the actual size. For example, for a 128 GiB disk local_gb will be 127, but size hint will be 128.

  • wwn (STRING): unique storage identifier

  • wwn_with_extension (STRING): unique storage identifier with the vendor extension appended

  • wwn_vendor_extension (STRING): unique vendor storage identifier

  • rotational (BOOLEAN): whether it’s a rotational device or not. This hint makes it easier to distinguish HDDs (rotational) and SSDs (not rotational) when choosing which disk Ironic should deploy the image onto.

  • hctl (STRING): the SCSI address (Host, Channel, Target and Lun), e.g ‘1:0:0:0’

  • name (STRING): the device name, e.g /dev/md0


    The root device hint name should only be used for devices with constant names (e.g RAID volumes). For SATA, SCSI and IDE disk controllers this hint is not recommended because the order in which the device nodes are added in Linux is arbitrary, resulting in devices like /dev/sda and /dev/sdb switching around at boot time.

To associate one or more hints with a node, update the node’s properties with a root_device key, for example:

openstack baremetal node set <node-uuid> --property root_device='{"wwn": "0x4000cca77fc4dba1"}'

That will guarantee that Bare Metal service will pick the disk device that has the wwn equal to the specified wwn value, or fail the deployment if it can not be found.

The hints can have an operator at the beginning of the value string. If no operator is specified the default is == (for numerical values) and s== (for string values). The supported operators are:

  • For numerical values:
    • = equal to or greater than. This is equivalent to >= and is supported for legacy reasons
    • == equal to
    • != not equal to
    • >= greater than or equal to
    • > greater than
    • <= less than or equal to
    • < less than
  • For strings (as python comparisons):
    • s== equal to
    • s!= not equal to
    • s>= greater than or equal to
    • s> greater than
    • s<= less than or equal to
    • s< less than
    • <in> substring
  • For collections:
    • <all-in> all elements contained in collection
    • <or> find one of these

Examples are:

  • Finding a disk larger or equal to 60 GiB and non-rotational (SSD):

    openstack baremetal node set <node-uuid> --property root_device='{"size": ">= 60", "rotational": false}'
  • Finding a disk whose vendor is samsung or winsys:

    openstack baremetal node set <node-uuid> --property root_device='{"vendor": "<or> samsung <or> winsys"}'


If multiple hints are specified, a device must satisfy all the hints.

Appending kernel parameters to boot instances

The Bare Metal service supports passing custom kernel parameters to boot instances to fit users’ requirements. The way to append the kernel parameters is depending on how to boot instances.

Network boot

Currently, the Bare Metal service supports assigning unified kernel parameters to PXE booted instances by:

  • Modifying the [pxe]/pxe_append_params configuration option, for example:

    pxe_append_params = quiet splash
  • Copying a template from shipped templates to another place, for example:

    Making the modifications and pointing to the custom template via the configuration options: [pxe]/pxe_config_template and [pxe]/uefi_pxe_config_template.

Local boot

For local boot instances, users can make use of configuration drive (see Enabling the configuration drive (configdrive)) to pass a custom script to append kernel parameters when creating an instance. This is more flexible and can vary per instance. Here is an example for grub2 with ubuntu, users can customize it to fit their use case:

#!/usr/bin/env python
import os

# Default grub2 config file in Ubuntu
grub_file = '/etc/default/grub'
# Add parameters here to pass to instance.
kernel_parameters = ['quiet', 'splash']
old_grub_file = grub_file+'~'
os.rename(grub_file, old_grub_file)
cmdline_existed = False
with open(grub_file, 'w') as writer, \
       open(old_grub_file, 'r') as reader:
       for line in reader:
           key = line.split('=')[0]
           if key == grub_cmd:
               #If there is already some value:
               if line.strip()[-1] == '"':
                   line = line.strip()[:-1] + ' ' + ' '.join(kernel_parameters) + '"'
               cmdline_existed = True
       if not cmdline_existed:
           line = grub_cmd + '=' + '"' + ' '.join(kernel_parameters) + '"'



In order to change default console configuration in the Bare Metal service configuration file ([pxe] section in /etc/ironic/ironic.conf), include the serial port terminal and serial speed. Serial speed must be the same as the serial configuration in the BIOS settings, so that the operating system boot process can be seen in the serial console or web console. Following examples represent possible parameters for serial and web console respectively.

  • Node serial console. The console parameter console=ttyS0,115200n8 uses ttyS0 for console output at 115200bps, 8bit, non-parity, e.g.:

    # Additional append parameters for baremetal PXE boot.
    pxe_append_params = nofb nomodeset vga=normal console=ttyS0,115200n8
  • For node web console configuration is similar with the addition of ttyX parameter, see example:

    # Additional append parameters for baremetal PXE boot.
    pxe_append_params = nofb nomodeset vga=normal console=tty0 console=ttyS0,115200n8

For detailed information on how to add consoles see the reference documents kernel params and serial console. In case of local boot the Bare Metal service is not able to control kernel boot parameters. To configure console locally, follow ‘Local boot’ section above.

Boot mode support

Most of the bare metal drivers (including the generic ipmi hardware type) support setting of boot mode (Legacy BIOS or UEFI). The boot modes can be configured in the Bare Metal service in the following way:

  • When no boot mode setting is provided, these drivers default the boot_mode to Legacy BIOS.

  • Only one boot mode (either uefi or bios) can be configured for the node.

  • If the operator wants a node to boot always in uefi mode or bios mode, then they may use capabilities parameter within properties field of an bare metal node. The operator must manually set the appropriate boot mode on the bare metal node.

    To configure a node in uefi mode, then set capabilities as below:

    openstack baremetal node set <node-uuid> --property capabilities='boot_mode:uefi'

    Nodes having boot_mode set to uefi may be requested by adding an extra_spec to the Compute service flavor:

    nova flavor-key ironic-test-3 set capabilities:boot_mode="uefi"
    nova boot --flavor ironic-test-3 --image test-image instance-1

    If capabilities is used in extra_spec as above, nova scheduler (ComputeCapabilitiesFilter) will match only bare metal nodes which have the boot_mode set appropriately in properties/capabilities. It will filter out rest of the nodes.

    The above facility for matching in the Compute service can be used in heterogeneous environments where there is a mix of uefi and bios machines, and operator wants to provide a choice to the user regarding boot modes. If the flavor doesn’t contain boot_mode and boot_mode is configured for bare metal nodes, then nova scheduler will consider all nodes and user may get either bios or uefi machine.

Choosing the disk label


The term disk label is historically used in Ironic and was taken from parted. Apparently everyone seems to have a different word for disk label - these are all the same thing: disk type, partition table, partition map and so on…

Ironic allows operators to choose which disk label they want their bare metal node to be deployed with when Ironic is responsible for partitioning the disk; therefore choosing the disk label does not apply when the image being deployed is a whole disk image.

There are some edge cases where someone may want to choose a specific disk label for the images being deployed, including but not limited to:

  • For machines in bios boot mode with disks larger than 2 terabytes it’s recommended to use a gpt disk label. That’s because a capacity beyond 2 terabytes is not addressable by using the MBR partitioning type. But, although GPT claims to be backward compatible with legacy BIOS systems that’s not always the case.
  • Operators may want to force the partitioning to be always MBR (even if the machine is deployed with boot mode uefi) to avoid breakage of applications and tools running on those instances.

The disk label can be configured in two ways; when Ironic is used with the Compute service or in standalone mode. The following bullet points and sections will describe both methods:

  • When no disk label is provided Ironic will configure it according to the boot mode (see Boot mode support); bios boot mode will use msdos and uefi boot mode will use gpt.
  • Only one disk label - either msdos or gpt - can be configured for the node.

When used with Compute service

When Ironic is used with the Compute service the disk label should be set to node’s properties/capabilities field and also to the flavor which will request such capability, for example:

openstack baremetal node set <node-uuid> --property capabilities='disk_label:gpt'

As for the flavor:

nova flavor-key baremetal set capabilities:disk_label="gpt"

When used in standalone mode

When used without the Compute service, the disk label should be set directly to the node’s instance_info field, as below:

openstack baremetal node set <node-uuid> --instance-info capabilities='{"disk_label": "gpt"}'

Trusted boot with partition image

The Bare metal service supports trusted boot with partition images. This means at the end of the deployment process, when the node is rebooted with the new user image, trusted boot will be performed. It will measure the node’s BIOS, boot loader, Option ROM and the Kernel/Ramdisk, to determine whether a bare metal node deployed by Ironic should be trusted.

It’s important to note that in order for this to work the node being deployed must have Intel TXT hardware support. The image being deployed with Ironic must have oat-client installed within it.

The following will describe how to enable trusted boot and boot with PXE and Nova:

  1. Create a customized user image with oat-client installed:

    disk-image-create -u fedora baremetal oat-client -o $TRUST_IMG

    For more information on creating customized images, see Create and add images to the Image service.

  2. Enable VT-x, VT-d, TXT and TPM on the node. This can be done manually through the BIOS. Depending on the platform, several reboots may be needed.

  3. Enroll the node and update the node capability value:

    openstack baremetal node create --driver ipmi
    openstack baremetal node set $NODE_UUID --property capabilities={'trusted_boot':true}
  4. Create a special flavor:

    nova flavor-key $TRUST_FLAVOR_UUID set 'capabilities:trusted_boot'=true
  5. Prepare tboot and mboot.c32 and put them into tftp_root or http_root directory on all nodes with the ironic-conductor processes:

        cp /usr/lib/syslinux/mboot.c32 /tftpboot/
        cp /usr/share/syslinux/mboot.c32 /tftpboot/

    Note: The actual location of mboot.c32 varies among different distribution versions.

    tboot can be downloaded from

  6. Install an OAT Server. An OAT Server should be running and configured correctly.

  7. Boot an instance with Nova:

    nova boot --flavor $TRUST_FLAVOR_UUID --image $TRUST_IMG --user-data $TRUST_SCRIPT trusted_instance

    Note that the node will be measured during trusted boot and the hash values saved into TPM. An example of TRUST_SCRIPT can be found in trust script example.

  8. Verify the result via OAT Server.

    This is outside the scope of Ironic. At the moment, users can manually verify the result by following the manual verify steps.


The Bare Metal service supports the emission of notifications, which are messages sent on a message broker (like RabbitMQ or anything else supported by the oslo messaging library) that indicate various events which occur, such as when a node changes power states. These can be consumed by an external service reading from the message bus. For example, Searchlight is an OpenStack service that uses notifications to index (and make searchable) resources from the Bare Metal service.

Notifications are disabled by default. For a complete list of available notifications and instructions for how to enable them, see the Notifications.

Configuring node web console

See Configuring Web or Serial Console.

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