Create flavors for use with the Bare Metal service

Create flavors for use with the Bare Metal service

Scheduling based on properties

You’ll need to create a special bare metal flavor in the Compute service. The flavor is mapped to the bare metal node through the hardware specifications.

  1. Change these to match your hardware:

    $ RAM_MB=1024
    $ CPU=2
    $ DISK_GB=100
    $ ARCH={i686|x86_64}
  2. Create the bare metal flavor by executing the following command:

    $ nova flavor-create my-baremetal-flavor auto $RAM_MB $DISK_GB $CPU


    You can replace auto with your own flavor id.

  3. Set the architecture as extra_specs information of the flavor. This will be used to match against the properties of bare metal nodes:

    $ nova flavor-key my-baremetal-flavor set cpu_arch=$ARCH

Scheduling based on resource classes

As of the Pike release, a Compute service flavor is able to use the node’s resource_class field (available starting with Bare Metal API version 1.21) for scheduling, instead of the CPU, RAM, and disk properties defined in the flavor. A flavor can request exactly one instance of a bare metal resource class.

Start with creating the flavor in the same way as described in Scheduling based on properties. The CPU, RAM_MB and DISK_GB values are not going to be used for scheduling, but the DISK_GB value will still be used to determine the root partition size.

After creation, associate each flavor with one custom resource class. The name of a custom resource class that corresponds to a node’s resource class (in the Bare Metal service) is:

  • the bare metal node’s resource class all upper-cased
  • prefixed with CUSTOM_
  • all punctuation replaced with an underscore

For example, if the resource class is named baremetal-small, associate the flavor with this custom resource class via:

$ nova flavor-key my-baremetal-flavor set resources:CUSTOM_BAREMETAL_SMALL=1

Another set of flavor properties should be used to disable scheduling based on standard properties for a bare metal flavor:

$ nova flavor-key my-baremetal-flavor set resources:VCPU=0
$ nova flavor-key my-baremetal-flavor set resources:MEMORY_MB=0
$ nova flavor-key my-baremetal-flavor set resources:DISK_GB=0


The last step will be mandatory in the Queens release, as the Compute service will stop providing standard resources for bare metal nodes.


If you want to define a class of nodes called baremetal.with-GPU, start with tagging some nodes with it:

$ openstack --os-baremetal-api-version 1.21 baremetal node set $NODE_UUID \
  --resource-class baremetal.with-GPU


It is possible to add a resource class to active nodes, but it is not possible to replace an existing resource class on them.

Then you can update your flavor to request the resource class instead of the standard properties:

$ nova flavor-key my-baremetal-flavor set resources:CUSTOM_BAREMETAL_WITH_GPU=1
$ nova flavor-key my-baremetal-flavor set resources:VCPU=0
$ nova flavor-key my-baremetal-flavor set resources:MEMORY_MB=0
$ nova flavor-key my-baremetal-flavor set resources:DISK_GB=0

Note how baremetal.with-GPU in the node’s resource_class field becomes CUSTOM_BAREMETAL_WITH_GPU in the flavor’s properties.

Scheduling based on traits

Starting with the Queens release, the Compute service supports scheduling based on qualitative attributes using traits. Starting with Bare Metal REST API version 1.37, it is possible to assign a list of traits to each bare metal node. Traits assigned to a bare metal node will be assigned to the corresponding resource provider in the Compute service placement API.

When creating a flavor in the Compute service, required traits may be specified via flavor properties. The Compute service will then schedule instances only to bare metal nodes with all of the required traits.

Traits can be either standard or custom. Standard traits are listed in the os_traits library. Custom traits must meet the following requirements:

  • prefixed with CUSTOM_
  • contain only upper case characters A to Z, digits 0 to 9, or underscores
  • no longer than 255 characters in length

A bare metal node can have a maximum of 50 traits.


To add the standard trait HW_CPU_X86_VMX and a custom trait CUSTOM_TRAIT1 to a node:

$ openstack --os-baremetal-api-version 1.37 baremetal node add trait \

Then, update the flavor to require these traits:

$ nova flavor-key my-baremetal-flavor set trait:CUSTOM_TRAIT1=required
$ nova flavor-key my-baremetal-flavor set trait:HW_CPU_X86_VMX=required
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