Host Configuration

This section covers configuration of hosts. It does not cover configuration or deployment of containers. Hosts that are configured by Kayobe include:

  • Seed hypervisor (kayobe seed hypervisor host configure)

  • Seed (kayobe seed host configure)

  • Overcloud (kayobe overcloud host configure)

Unless otherwise stated, all host configuration described here is applied to each of these types of host.

See also

Ansible tags for limiting the scope of Kayobe commands are included under the relevant sections of this page (for more information see Tags).

Configuration Location

Some host configuration options are set via global variables, and others have a variable for each type of host. The latter variables are included in the following files under ${KAYOBE_CONFIG_PATH}:

  • seed-hypervisor.yml

  • seed.yml

  • compute.yml

  • controller.yml

  • monitoring.yml

  • storage.yml

Note that any variable may be set on a per-host or per-group basis, by using inventory host or group variables - these delineations are for convenience.


Several directories are used by Kayobe on the remote hosts. There is a hierarchy of variables in ${KAYOBE_CONFIG_PATH}/globals.yml that can be used to control where these are located.

  • base_path (default /opt/kayobe/) sets the default base path for various directories.

  • config_path (default {{ base_path }}/etc) is a path in which to store configuration files.

  • image_cache_path (default {{ base_path }}/images) is a path in which to cache downloaded or built images.

  • source_checkout_path (default {{ base_path }}/src) is a path into which to store clones of source code repositories.

  • virtualenv_path (default {{ base_path }}/venvs) is a path in which to create Python virtual environments.

SSH Known Hosts


While strictly this configuration is applied to the Ansible control host (localhost), it is applied during the host configure commands. The ansible_host of each host is added as an SSH known host. This is typically the host’s IP address on the admin network (admin_oc_net_name), as defined in ${KAYOBE_CONFIG_PATH}/network-allocation.yml (see IP Address Allocation).

Kayobe User Bootstrapping


Kayobe uses a user account defined by the kayobe_ansible_user variable (in ${KAYOBE_CONFIG_PATH}/globals.yml) for remote SSH access. By default, this is stack.

Typically, the image used to provision these hosts will not include this user account, so Kayobe performs a bootstrapping step to create it, as a different user. In cloud images, there is often a user named after the OS distro, e.g. centos or ubuntu. This user defaults to the name of the user running Kayobe, but may be set via the following variables:

  • seed_hypervisor_bootstrap_user

  • seed_bootstrap_user

  • compute_bootstrap_user

  • controller_bootstrap_user

  • monitoring_bootstrap_user

  • storage_bootstrap_user

For example, to set the bootstrap user for controllers to centos:

controller_bootstrap_user: centos

PyPI Mirror and proxy


Kayobe supports configuration of a PyPI mirror and/or proxy, via variables in ${KAYOBE_CONFIG_PATH}/pip.yml. Mirror functionality is enabled by setting the pip_local_mirror variable to true and proxy functionality is enabled by setting pip_proxy variable to a proxy URL.

Kayobe will generate configuration for:

  • pip to use the mirror and proxy

  • easy_install to use the mirror

for the list of users defined by pip_applicable_users (default kayobe_ansible_user and root), in addition to the user used for Kolla Ansible (kolla_ansible_user). The mirror URL is configured via pip_index_url, and pip_trusted_hosts is a list of ‘trusted’ hosts, for which SSL verification will be disabled.

For example, to configure use of the test PyPI mirror at

pip_local_mirror: true

To configure use of the PyPI proxy:

pip_proxy: http://your_proxy_server:3128

Kayobe Remote Virtual Environment


By default, Ansible executes modules remotely using the system python interpreter, even if the Ansible control process is executed from within a virtual environment (unless the local connection plugin is used). This is not ideal if there are python dependencies that must be installed with isolation from the system python packages. Ansible can be configured to use a virtualenv by setting the host variable ansible_python_interpreter to a path to a python interpreter in an existing virtual environment.

If kayobe detects that ansible_python_interpreter is set and references a virtual environment, it will create the virtual environment if it does not exist. Typically this variable should be set via a group variable in the inventory for hosts in the seed, seed-hypervisor, and/or overcloud groups.

The default Kayobe configuration in the kayobe-config repository sets ansible_python_interpreter to {{ virtualenv_path }}/kayobe/bin/python for the seed, seed-hypervisor, and overcloud groups.

Disk Wiping


Using hosts that may have stale data on their disks could affect the deployment of the cloud. This is not a configuration option, since it should only be performed once to avoid losing useful data. It is triggered by passing the --wipe-disks argument to the host configure commands.

Users and Groups


Linux user accounts and groups can be configured using the users_default variable in ${KAYOBE_CONFIG_PATH}/users.yml. The format of the list is that used by the users variable of the singleplatform-eng.users role. The following variables can be used to set the users for specific types of hosts:

  • seed_hypervisor_users

  • seed_users

  • compute_users

  • controller_users

  • monitoring_users

  • storage_users

In the following example, a single user named bob is created. A password hash has been generated via mkpasswd --method=sha-512. The user is added to the wheel group, and an SSH key is authorised. The SSH public key should be added to the Kayobe configuration.

 - username: bob
   name: Bob
   password: "$6$wJt9MLWrHlWN8$oXJHbdaslm9guD5EC3Dry1mphuqF9NPeQ43OXk3cXZa2ze/F9FOTxm2KvvDkbdxBDs7ouwdiLTUJ1Ff40.cFU."
     - wheel
   append: True
     - "{{ lookup('file', kayobe_config_path ~ '/ssh-keys/') }}"

Package Repositories


Kayobe supports configuration of package repositories via DNF, via variables in ${KAYOBE_CONFIG_PATH}/dnf.yml.

Configuration of dnf.conf

Global configuration of DNF is stored in /etc/dnf/dnf.conf, and options can be set via the dnf_config variable. Options are added to the [main] section of the file. For example, to configure DNF to use a proxy server:


CentOS and EPEL Mirrors

CentOS and EPEL mirrors can be enabled by setting dnf_use_local_mirror to true. CentOS repository mirrors are configured via the following variables:

  • dnf_centos_mirror_host (default is the mirror hostname.

  • dnf_centos_mirror_directory (default centos) is a directory on the mirror in which repositories may be accessed.

EPEL repository mirrors are configured via the following variables:

  • dnf_epel_mirror_host (default is the mirror hostname.

  • dnf_epel_mirror_directory (default pub/epel) is a directory on the mirror in which repositories may be accessed.

For example, to configure CentOS and EPEL mirrors at

dnf_use_local_mirror: true

Custom DNF Repositories

It is also possible to configure a list of custom DNF repositories via the dnf_custom_repos variable. The format is a dict/map, with repository names mapping to a dict/map of arguments to pass to the Ansible yum_repository module.

For example, the following configuration defines a single DNF repository called widgets.

    file: widgets
    gpgcheck: yes

Disabling EPEL

It is possible to disable the EPEL DNF repository by setting dnf_install_epel to false.

DNF Automatic

DNF Automatic provides a mechanism for applying regular updates of packages. DNF Automatic is disabled by default, and may be enabled by setting dnf_automatic_enabled to true.

dnf_automatic_enabled:  true

By default, only security updates are applied. Updates for all packages may be installed by setting dnf_automatic_upgrade_type to default. This may cause the system to be less predictable as packages are updated without oversight or testing.



SELinux is not supported by Kolla Ansible currently, so it is disabled by Kayobe. If necessary, Kayobe will reboot systems in order to apply a change to the SELinux configuration. The timeout for waiting for systems to reboot is disable_selinux_reboot_timeout. Alternatively, the reboot may be avoided by setting disable_selinux_do_reboot to false.

Network Configuration


Configuration of host networking is covered in depth in Network Configuration.



Arbitrary sysctl configuration can be applied to hosts. The variable format is a dict/map, mapping parameter names to their required values. The following variables can be used to set sysctl configuration specific types of hosts:

  • seed_hypervisor_sysctl_parameters

  • seed_sysctl_parameters

  • compute_sysctl_parameters

  • controller_sysctl_parameters

  • monitoring_sysctl_parameters

  • storage_sysctl_parameters

For example, to set the net.ipv4.ip_forward parameter to 1 on controllers:

  net.ipv4.ip_forward: 1

Disable cloud-init


cloud-init is a popular service for performing system bootstrapping. If you are not using cloud-init, this section can be skipped.

If using the seed’s Bifrost service to provision the control plane hosts, the use of cloud-init may be configured via the kolla_bifrost_dib_init_element variable.

cloud-init searches for network configuration in order of increasing precedence; each item overriding the previous. In some cases, on subsequent boots cloud-init can automatically reconfigure network interfaces and cause some issues in network configuration. To disable cloud-init from running after the initial server bootstrapping, set disable_cloud_init to true in ${KAYOBE_CONFIG_PATH}/overcloud.yml.

Disable Glean


The glean service can be used to perform system bootstrapping, serving a similar role to cloud-init. If you are not using glean, this section can be skipped.

If using the seed’s Bifrost service to provision the control plane hosts, the use of glean may be configured via the kolla_bifrost_dib_init_element variable.

After the initial server bootstrapping, the glean service can cause problems as it attempts to enable all network interfaces, which can lead to timeouts while booting. To avoid this, the glean service is disabled. Additionally, any network interface configuration files generated by glean and not overwritten by Kayobe are removed.



The timezone can be configured via the timezone variable in ${KAYOBE_CONFIG_PATH}/time.yml. The value must be a valid Linux timezone. For example:

timezone: Europe/London


Since the Ussuri release, Kayobe no longer supports configuration of an NTP daemon on the host, since the ntp package is no longer available in CentOS 8.

Kolla Ansible can deploy a chrony container on overcloud hosts, and from the Ussuri release chrony is enabled by default. There is no support for running a chrony container on the seed or seed hypervisor hosts.

To disable the containerised chrony daemon, set the following in ${KAYOBE_CONFIG_PATH}/kolla.yml:

kolla_enable_chrony: false

Software RAID


While it is possible to use RAID directly with LVM, some operators may prefer the userspace tools provided by mdadm or may have existing software RAID arrays they want to manage with Kayobe.

Software RAID arrays may be configured via the mdadm_arrays variable. For convenience, this is mapped to the following variables:

  • seed_hypervisor_mdadm_arrays

  • seed_mdadm_arrays

  • compute_mdadm_arrays

  • controller_mdadm_arrays

  • monitoring_mdadm_arrays

  • storage_mdadm_arrays

The format of these variables is as defined by the mdadm_arrays variable of the mrlesmithjr.mdadm Ansible role.

For example, to configure two of the seed’s disks as a RAID1 mdadm array available as /dev/md0:

  - name: md0
      - /dev/sdb
      - /dev/sdc
    level: '1'
    state: present



Encrypted block devices may be configured via the luks_devices variable. For convenience, this is mapped to the following variables:

  • seed_hypervisor_luks_devices

  • seed_luks_devices

  • compute_luks_devices

  • controller_luks_devices

  • monitoring_luks_devices

  • storage_luks_devices

The format of these variables is as defined by the luks_devices variable of the stackhpc.luks Ansible role.

For example, to encrypt the software raid device, /dev/md0, on the seed, and make it available as /dev/mapper/md0crypt

  - name: md0crypt
    device: /dev/md0


It is not yet possible to encrypt the root device.



Logical Volume Manager (LVM) physical volumes, volume groups, and logical volumes may be configured via the lvm_groups variable. For convenience, this is mapped to the following variables:

  • seed_hypervisor_lvm_groups

  • seed_lvm_groups

  • compute_lvm_groups

  • controller_lvm_groups

  • monitoring_lvm_groups

  • storage_lvm_groups

The format of these variables is as defined by the lvm_groups variable of the mrlesmithjr.manage-lvm Ansible role.

LVM for libvirt

LVM is not configured by default on the seed hypervisor. It is possible to configure LVM to provide storage for a libvirt storage pool, typically mounted at /var/lib/libvirt/images.

To use this configuration, set the seed_hypervisor_lvm_groups variable to "{{ seed_hypervisor_lvm_groups_with_data }}" and provide a list of disks via the seed_hypervisor_lvm_group_data_disks variable.

LVM for Docker


In Train and earlier releases of Kayobe, the data volume group was always enabled by default.

If the devicemapper Docker storage driver is in use, the default LVM configuration is optimised for it. The devicemapper driver requires a thin provisioned LVM volume. A second logical volume is used for storing Docker volume data, mounted at /var/lib/docker/volumes. Both logical volumes are created from a single data volume group.

This configuration is enabled by the following variables, which default to true if the devicemapper driver is in use or false otherwise:

  • compute_lvm_group_data_enabled

  • controller_lvm_group_data_enabled

  • seed_lvm_group_data_enabled

  • storage_lvm_group_data_enabled

These variables can be set to true to enable the data volume group if the devicemapper driver is not in use. This may be useful where the docker-volumes logical volume is required.

To use this configuration, a list of disks must be configured via the following variables:

  • seed_lvm_group_data_disks

  • compute_lvm_group_data_disks

  • controller_lvm_group_data_disks

  • monitoring_lvm_group_data_disks

  • storage_lvm_group_data_disks

For example, to configure two of the seed’s disks for use by LVM:

  - /dev/sdb
  - /dev/sdc

The Docker volumes LVM volume is assigned a size given by the following variables, with a default value of 75% (of the volume group’s capacity):

  • seed_lvm_group_data_lv_docker_volumes_size

  • compute_lvm_group_data_lv_docker_volumes_size

  • controller_lvm_group_data_lv_docker_volumes_size

  • monitoring_lvm_group_data_lv_docker_volumes_size

  • storage_lvm_group_data_lv_docker_volumes_size

If using a Docker storage driver other than devicemapper, the remaining 25% of the volume group can be used for Docker volume data. In this case, the LVM volume’s size can be increased to 100%:

controller_lvm_group_data_lv_docker_volumes_size: 100%

If using a Docker storage driver other than devicemapper, it is possible to avoid using LVM entirely, thus avoiding the requirement for multiple disks. In this case, set the appropriate <host>_lvm_groups variable to an empty list:

storage_lvm_groups: []

Custom LVM

To define additional logical logical volumes in the default data volume group, modify one of the following variables:

  • seed_lvm_group_data_lvs

  • compute_lvm_group_data_lvs

  • controller_lvm_group_data_lvs

  • monitoring_lvm_group_data_lvs

  • storage_lvm_group_data_lvs

Include the variable <host>_lvm_group_data_lv_docker_volumes in the list to include the LVM volume for Docker volume data:

  - "{{ monitoring_lvm_group_data_lv_docker_volumes }}"
  - lvname: other-vol
    size: 1%
    create: true
    filesystem: ext4
    mount: true
    mntp: /path/to/mount

It is possible to define additional LVM volume groups via the following variables:

  • seed_lvm_groups_extra

  • compute_lvm_groups_extra

  • controller_lvm_groups_extra

  • monitoring_lvm_groups_extra

  • storage_lvm_groups_extra

For example:

  - vgname: other-vg
      - /dev/sdb
    create: true
      - lvname: other-vol
        size: 100%FREE
        create: true
        mount: false

Alternatively, replace the entire volume group list via one of the <host>_lvm_groups variables to replace the default configuration with a custom one.

  - vgname: only-vg
    disks: /dev/sdb
    create: true
      - lvname: only-vol
        size: 100%
        create: true
        mount: false

Kolla-Ansible bootstrap-servers

Kolla Ansible provides some host configuration functionality via the bootstrap-servers command, which may be leveraged by Kayobe.

See the Kolla Ansible documentation for more information on the functions performed by this command, and how to configure it.

Note that from the Ussuri release, Kayobe creates a user account for Kolla Ansible rather than this being done by Kolla Ansible during bootstrap-servers. See User account creation for details.

Kolla-Ansible Remote Virtual Environment


See Context: Remote Execution Environment for information about remote Python virtual environments for Kolla Ansible.

Docker Engine


Docker engine configuration is applied by both Kayobe and Kolla Ansible (during bootstrap-servers).

The docker_storage_driver variable sets the Docker storage driver, and by default the overlay2 driver is used. If using the devicemapper driver, see LVM for information about configuring LVM for Docker.

Various options are defined in ${KAYOBE_CONFIG_PATH}/docker.yml for configuring the devicemapper storage.

A private Docker registry may be configured via docker_registry, with a Certificate Authority (CA) file configured via docker_registry_ca.

To use one or more Docker Registry mirrors, use the docker_registry_mirrors variable.

If using an MTU other than 1500, docker_daemon_mtu can be used to configure this. This setting does not apply to containers using net=host (as Kolla Ansible’s containers do), but may be necessary when building images.

Docker’s live restore feature can be configured via docker_daemon_live_restore, although it is disabled by default due to issues observed.