TripleO config-download User’s Guide: Deploying with Ansible


This documentation details using config-download.

config-download is the feature that enables deploying the Overcloud software configuration with Ansible in TripleO.


Since the Queens release, it has been possible to use Ansible to apply the overcloud configuration and with the Rocky release it became the default.

Ansible is used to replace the communication and transport of the software configuration deployment data between Heat and the Heat agent (os-collect-config) on the overcloud nodes.

Instead of os-collect-config running on each overcloud node and polling for deployment data from Heat, the Ansible control node applies the configuration by running ansible-playbook with an Ansible inventory file and a set of playbooks and tasks.

The Ansible control node (the node running ansible-playbook) is the undercloud by default.

config-download is the feature name that enables using Ansible in this manner, and will often be used to refer to the method detailed in this documentation.

Heat is still used to create the stack, then the ansible playbooks are saved to the filesystem in a git repository. These playbook are used to deploy the openstack services and configuration to the Overcloud nodes. The same parameter values and environment files are passed to Heat as they were previously. During the stack creation, Heat simply takes the user inputs from the templates and renders the required playbooks for the deployment.

The difference with config-download is that although Heat creates all the deployment data necessary via SoftwareDeployment resources to perform the overcloud installation and configuration, it does not apply any of the software deployments. The data is only made available via the Heat API. Once the stack is created, deployment data is downloaded from Heat and ansible playbooks are generated.

Using the downloaded deployment data and ansible playbooks configuration of the overcloud using ansible-playbook are completed.

This diagram details the overall sequence of how using config-download completes an overcloud deployment:


Deployment with config-download

Ansible and config-download are used by default when openstack overcloud deploy (tripleoclient) is run. The command is backwards compatible in terms of functionality, meaning that running openstack overcloud deploy will still result in a full overcloud deployment.

The deployment is done through a series of steps in tripleoclient. All of the workflow steps are automated by tripleoclient. The workflow steps are summarized as:

  1. Create deployment plan

  2. Create Heat stack

  3. Create software configuration within the Heat stack

  4. Create tripleo-admin ssh user

  5. Download the software configuration from Heat

  6. Applying the downloaded software configuration to the overcloud nodes with ansible-playbook.

Creating the tripleo-admin user on each overcloud node is necessary since ansible uses ssh to connect to each node to perform configuration.

The following steps are done to create the tripleo-admin user:

  1. Runs a playbook to create tripleo-admin on each node. Also, gives sudo permissions to the user, as well as creates and stores a new ssh keypair for tripleo-admin.

The values for these cli arguments must be the same for all nodes in the overcloud deployment. overcloud-ssh-key should be the private key that corresponds with the public key specified by the Heat parameter KeyName when using Ironic deployed nodes.

Deployment Output

After the tripleo-admin user is created, ansible-playbook will be used to configure the overcloud nodes.

The output from ansible-playbook will begin to appear in the console and will be updated periodically as more tasks are applied.

When ansible is finished a play recap will be shown, and the usual overcloudrc details will then be displayed. The following is an example of the end of the output from a successful deployment:

PLAY RECAP ****************************************************************
compute-0                  : ok=134  changed=48   unreachable=0    failed=0
openstack-0                : ok=164  changed=28   unreachable=0    failed=1
openstack-1                : ok=160  changed=28   unreachable=0    failed=0
openstack-2                : ok=160  changed=28   unreachable=0    failed=0
pacemaker-0                : ok=138  changed=30   unreachable=0    failed=0
pacemaker-1                : ok=138  changed=30   unreachable=0    failed=0
pacemaker-2                : ok=138  changed=30   unreachable=0    failed=0
undercloud                 : ok=2    changed=0    unreachable=0    failed=0

Overcloud configuration completed.
Overcloud Endpoint:
Overcloud rc file: /home/stack/overcloudrc
Overcloud Deployed

When a failure happens, the deployment will stop and the error will be shown.

Review the PLAY RECAP which will show each host that is part of the overcloud and the grouped count of each task status.

Deployment Status

Since Heat is no longer the source of authority on the status of the overcloud deployment, a new tripleoclient command is available to show the overcloud deployment status:

openstack overcloud status

The output will report the status of the deployment, taking into consideration the result of all the steps to do the full deployment. The following is an example of the output:

[stack@undercloud ]$ openstack overcloud status

| Stack Name | Deployment Status |
| overcloud  |   DEPLOY_SUCCESS  |

A different stack name can be specified with --stack:

[stack@undercloud ]$ openstack overcloud status --stack my-deployment

| Stack Name    | Deployment Status |
| my-deployment |   DEPLOY_SUCCESS  |

The deployment status is stored in the YAML file, generated at $HOME/overcloud-deploy/<stack>/<stack>-deployment_status.yaml in the undercloud node.

Deployment Log

The ansible part of the deployment creates a log file that is saved on the undercloud. The log file is available at $HOME/ansible.log.

Ansible configuration

When ansible-playbook runs, it will use a configuration file with the following default values:

retry_files_enabled = False
log_path = <working directory>/ansible.log
forks = 25

ssh_args = -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o ControlMaster=auto -o ControlPersist=60s
control_path_dir = <working directory>/ansible-ssh

Any of the above configuration options can be overridden, or any additional ansible configuration used by passing the path to an ansible configuration file with --override-ansible-cfg on the deployment command.

For example the following command will use the configuration options from /home/stack/ansible.cfg. Any options specified in the override file will take precedence over the defaults:

openstack overcloud deploy \
  --override-ansible-cfg /home/stack/ansible.cfg

Ansible project directory

The workflow will create an Ansible project directory with the plan name under $HOME/overcloud-deploy/<stack>/config-download. For the default plan name of overcloud the working directory will be:


The project directory is where the downloaded software configuration from Heat will be saved. It also includes other ansible-related files necessary to run ansible-playbook to configure the overcloud.

The contents of the project directory include the following files:


Ansible inventory file containing hosts and vars for all the overcloud nodes.


Log file from the last run of ansible-playbook.


Config file used when running ansible-playbook.

Executable script that can be used to rerun ansible-playbook.


Private ssh key used to ssh to the overcloud nodes.

Reproducing ansible-playbook

Once in the project directory created, simply run to reproduce the deployment:


Any additional arguments passed to this script will be passed unchanged to the ansible-playbook command:

./ --check

Using this method it is possible to take advantage of various Ansible features, such as check mode (--check), limiting hosts (--limit), or overriding variables (-e).

Git repository

The ansible project directory is a git repository. Each time config-download downloads the software configuration data from Heat, the project directory will be checked for differences. A new commit will be created if there are any changes from the previous revision.

From within the ansible project directory, standard git commands can be used to explore each revision. Commands such as git log, git show, and git diff are useful ways to describe how each commit to the software configuration differs from previous commits.

Applying earlier versions of configuration

Using commands such as git revert or git checkout, it is possible to update the ansible project directory to an earlier version of the software configuration.

It is possible to then apply this earlier version with ansible-playbook. However, caution should be exercised as this could lead to a broken overcloud deployment. Only well understood earlier versions should be attempted to be applied.


Data migration changes will never be undone by applying an earlier version of the software configuration with config-download. For example, database schema migrations that had already been applied would never be undone by only applying an earlier version of the configuration.

Software changes that were related to hardware changes in the overcloud (such as scaling up or down) would also not be completely undone by applying earlier versions of the software configuration.


Reverting to earlier revisions of the project directory has no effect on the configuration stored in the Heat stack. A corresponding change should be made to the deployment templates, and the stack updated to make the changes permanent.

Manual config-download

Prior to running the ansible playbooks generated by config-download, it is necessary to ensure the baremetal nodes have already been provisioned. See the baremetal deployment guide first:


The config-download steps can be skipped when running openstack overcloud deploy by passing --stack-only. This will cause tripleoclient to only deploy the Heat stack.

When running openstack overcloud deploy with the --stack-only option, this will still download the ansible content to the default directory $HOME/overcloud-deploy/overcloud/config-download. But it will stop before running the ansible-playbook command.

This method is described in the following sections.

Run ansible-playbook

Once the baremetal nodes have been configured, and the configuration has been downloaded during the --stack-only run of openstack overcloud deploy. You can then run ansible-playbook manually to configure the overcloud nodes:

ansible-playbook \
  -i /home/stack/config-download/overcloud/tripleo-ansible-inventory.yaml \
  --private-key /path/private/ssh/key \
  --become \


--become is required when running ansible-playbook.

All default ansible configuration values will be used when manually running ansible-playbook in this manner. These values can be customized through ansible configuration.

The following minimum configuration is recommended:

log_path = ansible.log
forks = 25
timeout = 30

ssh_args = -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o ControlMaster=auto -o ControlPersist=30m
retries = 8
pipelining = True


When running ansible-playbook manually, the overcloud status as returned by openstack overcloud status won’t be automatically updated due to the configuration being applied outside of the API.

See Deployment Status for setting the status manually.

Ansible project directory contents

This section details the structure of the config-download generated Ansible project directory.



Initial deployment or template update (not minor update)

Further detailed in deploy_steps_playbook.yaml


Fast forward upgrades


Post upgrade steps for major upgrade


Pre upgrade steps for major upgrade


Minor update steps


Major upgrade steps


deploy_steps_playbook.yaml is the playbook used for deployment and template update. It applies all the software configuration necessary to deploy a full overcloud based on the templates provided as input to the deployment command.

This section will summarize at high level the different ansible plays used within this playbook. The play names shown here are the same names used within the playbook and are what will be shown in the output when ansible-playbook is run.

The ansible tags set on each play are also shown below.

Gather facts from undercloud

Fact gathering for the undercloud node

tags: facts

Gather facts from overcloud

Fact gathering for the overcloud nodes

tags: facts

Load global variables

Loads all variables from l`global_vars.yaml`

tags: always

Common roles for TripleO servers

Applies common ansible roles to all overcloud nodes. Includes tripleo_bootstrap for installing bootstrap packages and tripleo_ssh_known_hosts for configuring ssh known hosts.

tags: common_roles

Overcloud deploy step tasks for step 0

Applies tasks from the deploy_steps_tasks template interface

tags: overcloud, deploy_steps

Server deployments

Applies server specific Heat deployments for configuration such as networking and hieradata. Includes NetworkDeployment, <Role>Deployment, <Role>AllNodesDeployment, etc.

tags: overcloud, pre_deploy_steps

Host prep steps

Applies tasks from the host_prep_steps template interface

tags: overcloud, host_prep_steps

External deployment step [1,2,3,4,5]

Applies tasks from the external_deploy_steps_tasks template interface. These tasks are run against the undercloud node only.

tags: external, external_deploy_steps

Overcloud deploy step tasks for [1,2,3,4,5]

Applies tasks from the deploy_steps_tasks template interface

tags: overcloud, deploy_steps

Overcloud common deploy step tasks [1,2,3,4,5]

Applies the common tasks done at each step to include puppet host configuration,, and paunch or tripleo_container_manage Ansible role (container configuration).

tags: overcloud, deploy_steps

Server Post Deployments

Applies server specific Heat deployments for configuration done after the 5 step deployment process.

tags: overcloud, post_deploy_steps

External deployment Post Deploy tasks

Applies tasks from the external_post_deploy_steps_tasks template interface. These tasks are run against the undercloud node only.

tags: external, external_deploy_steps

Task files

These task files include tasks specific to their intended function. The task files are automatically used by specific playbooks from the previous section.

















Heat Role directories

Each Heat role from the roles data file used in the deployment (specified with -r from the openstack overcloud deploy command), will have a correspondingly named directory.

When using the default roles, these directories would be:






A given role directory contains role specific task files and a subdirectory for each host for that role. For example, when using the default hostnames, the Controller role directory would contain the following host subdirectories:




Other files

Other files in the project directory are:

Script to reproduce ansible-playbook command


Ansible inventory file


Tarball of Ansible project directory

Running specific tasks

Running only specific tasks (or skipping certain tasks) can be done from within the ansible project directory.


Running specific tasks is an advanced use case and only recommended for specific scenarios where the deployer is aware of the impact of skipping or only running certain tasks.

This can be useful during troubleshooting and debugging scenarios, but should be used with caution as it can result in an overcloud that is not fully configured.


All tasks that are part of the deployment need to be run, and in the order specified. When skipping tasks with --tags, -skip-tags, --start-at-task, the deployment could be left in an inoperable state.

The functionality to skip tasks or only run certain tasks is meant to aid in troubleshooting and iterating more quickly on failing deployments and updates.

All changes to the deployed cloud must still be applied through the Heat templates and environment files passed to the openstack overcloud deploy command. Doing so ensures that the deployed cloud is kept in sync with the state of the templates and the state of the Heat stack.


When skipping tasks, the overcloud must be in the state expected by the task starting task. Meaning, the state of the overcloud should be the same as if all the skipped tasks had been applied. Otherwise, the result of the tasks that get executed will be undefined and could leave the cloud in an inoperable state.

Likewise, the deployed cloud may not be left in its fully configured state if tasks are skipped at the end of the deployment.

Complete the Manual config-download steps to create the ansible project directory, or use the existing project directory at $HOME/overcloud-deploy/<stack-name>/config-download/<stack-name>.


The playbooks use tagged tasks for finer-grained control of what to apply if desired. Tags can be used with the ansible-playbook CLI arguments --tags or --skip-tags to control what tasks are executed. The enabled tags are:


fact gathering


ansible roles common to all nodes


all plays for overcloud deployment


deployments that happen pre deploy_steps


Host preparation steps


deployment steps


deployments that happen post deploy_steps


all external deployments


external deployments that run on the undercloud

See deploy_steps_playbook.yaml for a description of which tags apply to specific plays in the deployment playbook.

Server specific pre and post deployments

The list of server specific pre and post deployments run during the Server deployments and Server Post Deployments plays (see deploy_steps_playbook.yaml) are dependent upon what custom roles and templates are used with the deployment.

The list of these tasks are defined in an ansible group variable that applies to each server in the inventory group named after the Heat role. From the ansible project directory, the value can be seen within the group variable file named after the Heat role:

$ cat group_vars/Compute
  - UpgradeInitDeployment
  - HostsEntryDeployment
  - DeployedServerBootstrapDeployment
  - InstanceIdDeployment
  - NetworkDeployment
  - ComputeUpgradeInitDeployment
  - ComputeDeployment
  - ComputeHostsDeployment
  - ComputeAllNodesDeployment
  - ComputeAllNodesValidationDeployment
  - ComputeHostPrepDeployment
  - ComputeArtifactsDeploy

Compute_post_deployments:  []

<Role>_pre_deployments is the list of pre deployments, and <Role>_post_deployments is the list of post deployments.

To specify the specific task to run for each deployment, the value of the variable can be defined on the command line when running ansible-playbook, which will overwrite the value from the group variable file for that role.

For example:

ansible-playbook \
  -e Compute_pre_deployments=NetworkDeployment \
  --tags pre_deploy_steps
  # other CLI arguments

Using the above example, only the task for the NetworkDeployment resource would get applied since it would be the only value defined in Compute_pre_deployments, and --tags pre_deploy_steps is also specified, causing all other plays to get skipped.

Starting at a specific task

To start the deployment at a specific task, use the ansible-playbook CLI argument --start-at-task. To see a list of task names for a given playbook, --list-tasks can be used to list the task names.


Some tasks that include the step variable or other ansible variables in the task name do not work with --start-at-task due to a limitation in ansible. For example the task with the name:

Start containers for step 1

won’t work with --start-at-task since the step number is in the name (1).

When using --start-at-task, the tasks that gather facts and load global variables for the playbook execution are skipped by default. Skipping those tasks can cause unexpected errors in later tasks. To avoid errors, those tasks can be forced to execute when using --start-at-task by including the following options to the ansible-playbook command:

ansible-playbook \
  <other options > \
  -e gather_facts=true \
  -e @global_vars.yaml

The global_vars.yaml variable file exists in the config-download directory that was either generated manually or under $HOME/config-download.

Previewing changes

Changes can be previewed to see what will be changed before any changes are applied to the overcloud. To preview changes, the stack update must be run with the --stack-only cli argument:

openstack overcloud deploy \
  # other CLI arguments

When ansible-playbook is run, use the --check CLI argument with ansible-playbook to preview any changes. The extent to which changes can be previewed is dependent on many factors such as the underlying tools in use (puppet, docker, etc) and the support for ansible check mode in the given ansible module.

The --diff option can also be used with --check to show the differences that would result from changes.

See Ansible Check Mode (“Dry Run”) for more details.