CentOS 8

This section covers use of Kayobe on CentOS 8 in the Train release. From the 7.1.0 release, Kayobe supports both CentOS 7 and 8. However, CentOS 7 is used by default, and some configuration changes are required to use CentOS 8.

Currently this documentation focuses on greenfield deployments. More information about migrating from CentOS 7 to CentOS 8 will be provided soon.

See the Kolla Ansible documentation for information on using CentOS 8.

Container images

To support both CentOS 7 and 8, for the Train release only, Kolla publishes images to Dockerhub with the following tags:

CentOS version






Building container images

For details on how to build container images based on CentOS 8, see the Kolla image building guide. If building images locally, the base image tag should be configured to use a CentOS 8 image.

base_tag = 8

Also, the tag applied to the built images should be modified to match that expected by Kolla Ansible.

kolla_tag: train-centos8

See Global Configuration for further information.

Deploying container images

For the Train release only, Kolla Ansible applies a -centos8 suffix (configured via openstack_tag_suffix) to image tags by default on CentOS 8 hosts. The default tag is therefore train-centos8. If using a custom tag, modify kolla_openstack_release:

kolla_openstack_release: my-tag

This would result in Kolla Ansible using my-tag on CentOS 7 and my-tag-centos8 on CentOS 8.

If you do not want the suffix to be applied, it may be set to an empty string:

openstack_tag_suffix: ""

If you are using different tags for each service or image, and still want the suffix to be applied (e.g. if migrating from CentOS 7 to 8), use a pattern like the following:

nova_tag: "my-nova-tag{% raw %}{{ openstack_tag_suffix }}{% endraw %}"

Seed VM

By default, a CentOS 7 image is used to create the seed VM. This can be changed via seed_vm_root_image. For example, to use the upstream CentOS 8.2 cloud image:

seed_vm_root_image: https://cloud.centos.org/centos/8/x86_64/images/CentOS-8-GenericCloud-8.4.2105-20210603.0.x86_64.qcow2

Migrating a Seed VM to CentOS 8

By default, a seed VM is provisioned with separate root and data libvirt volumes. If Docker volumes are stored on the data libvirt volume, a CentOS 7 seed VM can be easily migrated to CentOS 8 using the following instructions.


Backing up the seed VM is strongly recommended before attempting the migration. All data stored in the root libvirt volume will be lost.

On the seed hypervisor, shut down the seed VM and delete its root libvirt volume, assuming that the seed VM is named seed and the libvirt storage pool for the seed VM is named default.

$ sudo virsh shutdown seed
$ sudo virsh vol-delete seed-root --pool default

Update seed_vm_root_image in ${KAYOBE_CONFIG_PATH}/seed-vm.yml to point to a CentOS 8 image, as described earlier.

Reprovision the seed VM and configure its host OS:

(kayobe) $ kayobe seed vm provision
(kayobe) $ kayobe seed host configure

Update the Kayobe configuration to build container images based on CentOS 8, as described in Building container images, and rebuild the bifrost image:

(kayobe) $ kayobe seed container image build bifrost-deploy

Finally, redeploy Bifrost:

(kayobe) $ kayobe seed service deploy

Ironic Python Agent (IPA)

If building IPA images locally, by default a CentOS 7 based ramdisk will be built. This can be changed via the following configuration:

  - centos
  - enable-serial-console
  - ironic-python-agent-ramdisk


  - repo: "https://opendev.org/openstack/ironic-python-agent-builder"
    local: "{{ source_checkout_path }}/ironic-python-agent-builder"
    version: "master"
    elements_path: "dib"

ipa_build_upper_constraints_file: "https://releases.openstack.org/constraints/upper/victoria"

  - "ipa.kernel"
  - "ipa.initramfs"

To install the hardware package necessary to use the extra-hardware collector, the ironic-python-agent-builder repository provides an extra-hardware element. It may be used as follows if building an IPA image locally:

  - "extra-hardware"

Alternatively, if you are downloading IPA images, you should apply the following configuration to use CentOS 8:

ipa_kernel_upstream_url: "https://tarballs.openstack.org/ironic-python-agent/dib/files/ipa-centos8{{ ipa_images_upstream_url_suffix }}.kernel"
ipa_ramdisk_upstream_url: "https://tarballs.openstack.org/ironic-python-agent/dib/files/ipa-centos8{{ ipa_images_upstream_url_suffix }}.initramfs"

After the images are built or downloaded, you will need to rename the kernel from ipa.kernel to ipa.vmlinuz. On the seed host, run:

docker exec bifrost_deploy mv /httpboot/ipa.kernel /httpboot/ipa.vmlinuz

See Ironic Python Agent (IPA) for further information.

Overcloud root disk

The overcloud root disk is based on CentOS 7 by default. This can be changed via the following configuration:

kolla_bifrost_dib_os_element: centos
kolla_bifrost_dib_os_release: 8

Note that the version of diskimage-builder in the bifrost_deploy container on the seed must be at least 2.35 for CentOS 8 support.

See Bifrost for further information.