Manage Flavors

Admin users can use the openstack flavor command to customize and manage flavors. To see information for this command, run:

$ openstack flavor --help
Command "flavor" matches:
  flavor create
  flavor delete
  flavor list
  flavor set
  flavor show
  flavor unset


Configuration rights can be delegated to additional users by redefining the access controls for os_compute_api:os-flavor-manage:create, os_compute_api:os-flavor-manage:update and os_compute_api:os-flavor-manage:delete in /etc/nova/policy.yaml on the nova-api server.


Flavor customization can be limited by the hypervisor in use. For example the libvirt driver enables quotas on CPUs available to a VM, disk tuning, bandwidth I/O, watchdog behavior, random number generator device control, and instance VIF traffic control.

For information on the flavors and flavor extra specs, refer to Flavors.

Create a flavor

  1. List flavors to show the ID and name, the amount of memory, the amount of disk space for the root partition and for the ephemeral partition, the swap, and the number of virtual CPUs for each flavor:

    $ openstack flavor list
  2. To create a flavor, specify a name, ID, RAM size, disk size, and the number of vCPUs for the flavor, as follows:

    $ openstack flavor create FLAVOR_NAME --id FLAVOR_ID \
        --ram RAM_IN_MB --disk ROOT_DISK_IN_GB --vcpus NUMBER_OF_VCPUS


    Unique ID (integer or UUID) for the new flavor. If specifying ‘auto’, a UUID will be automatically generated.

    Here is an example that creates a public m1.extra_tiny flavor that automatically gets an ID assigned, with 256 MB memory, no disk space, and one VCPU.

    $ openstack flavor create --public m1.extra_tiny --id auto \
        --ram 256 --disk 0 --vcpus 1
  3. If an individual user or group of users needs a custom flavor that you do not want other projects to have access to, you can create a private flavor.

    $ openstack flavor create --private m1.extra_tiny --id auto \
        --ram 256 --disk 0 --vcpus 1

    After you create a flavor, assign it to a project by specifying the flavor name or ID and the project ID:

    $ openstack flavor set --project PROJECT_ID m1.extra_tiny

    For a list of optional parameters, run this command:

    $ openstack help flavor create
  4. In addition, you can set or unset properties, commonly referred to as “extra specs”, for the existing flavor. The extra_specs metadata keys can influence the instance directly when it is launched. If a flavor sets the quota:vif_outbound_peak=65536 extra spec, the instance’s outbound peak bandwidth I/O should be less than or equal to 512 Mbps. There are several aspects that can work for an instance including CPU limits, Disk tuning, Bandwidth I/O, Watchdog behavior, and Random-number generator. For information about available metadata keys, see Flavors.

    For a list of optional parameters, run this command:

    $ openstack flavor set --help

Modify a flavor

Only the description of flavors can be modified (starting from microversion 2.55). To modify the description of a flavor, specify the flavor name or ID and a new description as follows:

$ openstack --os-compute-api-version 2.55 flavor set --description <DESCRIPTION> <FLAVOR>


The only field that can be updated is the description field. Nova has historically intentionally not included an API to update a flavor because that would be confusing for instances already created with that flavor. Needing to change any other aspect of a flavor requires deleting and/or creating a new flavor.

Nova stores a serialized version of the flavor associated with an instance record in the instance_extra table. While nova supports updating flavor extra_specs it does not update the embedded flavor in existing instances. Nova does not update the embedded flavor as the extra_specs change may invalidate the current placement of the instance or alter the compute context that has been created for the instance by the virt driver. For this reason admins should avoid updating extra_specs for flavors used by existing instances. A resize can be used to update existing instances if required but as a resize performs a cold migration it is not transparent to a tenant.

Delete a flavor

To delete a flavor, specify the flavor name or ID as follows:

$ openstack flavor delete FLAVOR

Default Flavors

Previous versions of nova typically deployed with default flavors. This was removed from Newton. The following table lists the default flavors for Mitaka and earlier.



Disk (in GB)

RAM (in MB)