Juju Charm - Nova Cloud Controller
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The nova-cloud-controller charm deploys a suite of OpenStack Nova services:



This section covers common and/or important configuration options. See file config.yaml for the full list of options, along with their descriptions and default values. See the Juju documentation for details on configuring applications.


Controls whether or not the charm will use the current cache for hostname/IP resolution queries for nova-compute units. This occurs whenever information that is passed over the nova-compute:cloud-compute relation changes (e.g. a nova-compute unit is added). The default value is 'true'. See section SSH host lookup caching for details.


Sets a client accessible proxy IP address that allows for VM console access. It should route to the nova-cloud-controller unit when the application is not under HA. When it is, the value of 'local' will point to the VIP.

Ensure that option console-access-protocol is set to a value other than 'None'.

VNC clients should be configured accordingly. In the case of a VIP, it will need to be determined.


Specifies the protocol to use when accessing the console of a VM. Supported values are: 'None', 'spice', 'xvpvnc', 'novnc', and 'vnc' (for both xvpvnc and novnc). Type 'xvpvnc' is not supported with UCA release 'bionic-ussuri' or with series 'focal' or later.

Caution: VMs are configured with a specific protocol at creation time. Console access for existing VMs will therefore break if this value is changed to something different.


Defines the network manager for the cloud. Supported values are:

  • 'FlatDHCPManager' for nova-network (the default)
  • 'FlatManager' - for nova-network
  • 'Neutron' - for a full SDN solution

When using 'Neutron' the neutron-gateway charm should be used to provide L3 routing and DHCP Services.


States the software sources. A common value is an OpenStack UCA release (e.g. 'cloud:bionic-ussuri' or 'cloud:focal-wallaby'). See Ubuntu Cloud Archive. The underlying host's existing apt sources will be used if this option is not specified (this behaviour can be explicitly chosen by using the value of 'distro').


These deployment instructions assume the following applications are present: keystone, rabbitmq-server, neutron-api, nova-compute, and a cloud database.

File ncc.yaml contains an example configuration:

     network-manager: Neutron
     openstack-origin: cloud:focal-wallaby

Nova cloud controller is often containerised. Here a single unit is deployed to a new container on machine '3':

juju deploy --to lxd:3 --config ncc.yaml nova-cloud-controller

Note: The cloud's database is determined by the series: prior to focal percona-cluster is used, otherwise it is mysql-innodb-cluster. In the example deployment below mysql-innodb-cluster is used.

Join nova-cloud-controller to the cloud database:

juju deploy mysql-router ncc-mysql-router
juju add-relation ncc-mysql-router:db-router mysql-innodb-cluster:db-router
juju add-relation ncc-mysql-router:shared-db nova-cloud-controller:shared-db

Five additional relations can be added:

juju add-relation nova-cloud-controller:identity-service keystone:identity-service
juju add-relation nova-cloud-controller:amqp rabbitmq-server:amqp
juju add-relation nova-cloud-controller:neutron-api neutron-api:neutron-api
juju add-relation nova-cloud-controller:cloud-compute nova-compute:cloud-compute


Enable TLS by adding a relation to an existing vault application:

juju add-relation nova-cloud-controller:certificates vault:certificates

See Managing TLS certificates in the OpenStack Charms Deployment Guide for more information on TLS.

Note: This charm also supports TLS configuration via charm options ssl_cert, ssl_key, and ssl_ca.


This section covers Juju actions supported by the charm. Actions allow specific operations to be performed on a per-unit basis. To display action descriptions run juju actions --schema nova-cloud-controller. If the charm is not deployed then see file actions.yaml.

  • archive-data
  • clear-unit-knownhost-cache
  • openstack-upgrade
  • pause
  • resume
  • security-checklist
  • sync-compute-availability-zones

High availability

When more than one unit is deployed with the hacluster application the charm will bring up an HA active/active cluster.

There are two mutually exclusive high availability options: using virtual IP(s) or DNS. In both cases the hacluster subordinate charm is used to provide the Corosync and Pacemaker backend HA functionality.

See OpenStack high availability in the OpenStack Charms Deployment Guide for details.


This charm supports the use of Juju Network Spaces, allowing the charm to be bound to network space configurations managed directly by Juju. This is only supported with Juju 2.0 and above.

API endpoints can be bound to distinct network spaces supporting the network separation of public, internal and admin endpoints.

Access to the underlying MySQL instance can also be bound to a specific space using the shared-db relation.

To use this feature, use the --bind option when deploying the charm:

juju deploy nova-cloud-controller --bind \
   "public=public-space \
    internal=internal-space \
    admin=admin-space \

Alternatively, these can also be provided as part of a Juju native bundle configuration:

      charm: cs:xenial/nova-cloud-controller
      num_units: 1
        public: public-space
        admin: admin-space
        internal: internal-space
        shared-db: internal-space

Note: Spaces must be configured in the underlying provider prior to attempting to use them.

Note: Existing deployments using os-*-network configuration options will continue to function; these options are preferred over any network space binding provided if set.

Charm-managed quotas

The charm can optionally set project quotas, which affect both new and existing projects. These quotas are set with the following configuration options:

  • quota-cores
  • quota-count-usage-from-placement
  • quota-injected-files
  • quota-injected-file-size
  • quota-injected-path-size
  • quota-instances
  • quota-key-pairs
  • quota-metadata-items
  • quota-ram
  • quota-server-groups
  • quota-server-group-members

Given that OpenStack quotas can be set in a variety of ways, the order of precedence (from higher to lower) for the enforcing of quotas is:

  1. quotas set by the operator manually
  2. quotas set by the nova-cloud-controller charm
  3. default quotas of the OpenStack service

For information on OpenStack quotas see Manage quotas in the Nova documentation.

SSH host lookup caching

Caching SSH known hosts reduces 'cloud-compute' hook execution time. It does this by reducing the number of lookups performed by the nova-cloud-controller charm during SSH connection negotiations when distributing a new unit's SSH keys among existing units of the same application group. These keys are needed for VM migrations to succeed.

The cache is populated (or refreshed) when option cache-known-hosts is set to 'false', in which case DNS lookups are always performed. The cache is queried by the charm when it is set to 'true', where a lookup is only performed (adding the result to the cache) when the cache is unable satisfy the query.

When a modification is made to DNS resolution, the clear-unit-knownhost-cache action should be used. This action refreshes the charm's cache and updates the known_hosts file on the nova-compute units. Information can be updated selectively by targeting a specific unit, an application group, or all application groups:

juju run-action --wait nova-cloud-controller/0 clear-unit-knownhost-cache target=nova-compute/2
juju run-action --wait nova-cloud-controller/0 clear-unit-knownhost-cache target=nova-compute
juju run-action --wait nova-cloud-controller/0 clear-unit-knownhost-cache

When nova-cloud-controller is under HA, the same invocation must be run on all nova-cloud-controller units.

Policy overrides

Policy overrides is an advanced feature that allows an operator to override the default policy of an OpenStack service. The policies that the service supports, the defaults it implements in its code, and the defaults that a charm may include should all be clearly understood before proceeding.

Caution: It is possible to break the system (for tenants and other services) if policies are incorrectly applied to the service.

Policy statements are placed in a YAML file. This file (or files) is then (ZIP) compressed into a single file and used as an application resource. The override is then enabled via a Boolean charm option.

Here are the essential commands (filenames are arbitrary):

zip overrides.zip override-file.yaml
juju attach-resource nova-cloud-controller policyd-override=overrides.zip
juju config nova-cloud-controller use-policyd-override=true

See appendix Policy overrides in the OpenStack Charms Deployment Guide for a thorough treatment of this feature.


The OpenStack Charms project maintains two documentation guides:


Please report bugs on Launchpad.