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Transitioning to Containerized Services

Red Hat OpenStack Platform 14

A basic guide to working with OpenStack Platform containerized services

OpenStack Documentation Team


This guide provides some basic information to help users get accustomed working with OpenStack Platform services running in containers.

Chapter 1. Introduction

Past versions of Red Hat OpenStack Platform used services managed with Systemd. However, more recent version of OpenStack Platform now use containers to run services. Some administrators might not have a good understanding of how containerized OpenStack Platform services operate, and so this guide aims to help you understand OpenStack Platform container images and containerized services. This includes:

  • How to obtain and modify container images
  • How to manage containerized services in the overcloud
  • Understanding how containers differ from Systemd services

The main goal is to help you gain enough knowledge of containerized OpenStack Platform services to transition from a Systemd-based environment to a container-based environment.

1.1. Containerized Services and Kolla

Each of the main Red Hat OpenStack Platform services run in containers. This provides a method of keep each service within its own isolated namespace separated from the host. This means:

  • The deployment of services is performed by pulling container images from the Red Hat Custom Portal and running them.
  • The management functions, like starting and stopping services, operate through the docker command.
  • Upgrading containers require pulling new container images and replacing the existing containers with newer versions.

Red Hat OpenStack Platform uses a set of containers built and managed with the kolla toolset.

Chapter 2. Obtaining and modifying container images

A containerized overcloud requires access to a registry with the required container images. This chapter provides information on how to prepare the registry and your undercloud and overcloud configuration to use container images for Red Hat OpenStack Platform.

2.1. Preparing container images

The overcloud configuration requires initial registry configuration to determine where to obtain images and how to store them. Complete the following steps to generate and customize an environment file for preparing your container images.


  1. Log in to your undercloud host as the stack user.
  2. Generate the default container image preparation file:

    $ openstack tripleo container image prepare default \
      --local-push-destination \
      --output-env-file containers-prepare-parameter.yaml

    This command includes the following additional options:

    • --local-push-destination sets the registry on the undercloud as the location for container images. This means the director pulls the necessary images from the Red Hat Container Catalog and pushes them to the registry on the undercloud. The director uses this registry as the container image source. To pull directly from the Red Hat Container Catalog, omit this option.
    • --output-env-file is an environment file name. The contents of this file include the parameters for preparing your container images. In this case, the name of the file is containers-prepare-parameter.yaml.


      You can also use the same containers-prepare-parameter.yaml file to define a container image source for both the undercloud and the overcloud.

  3. Edit the containers-prepare-parameter.yaml and make the modifications to suit your requirements.

2.2. Container image preparation parameters

The default file for preparing your containers (containers-prepare-parameter.yaml) contains the ContainerImagePrepare Heat parameter. This parameter defines a list of strategies for preparing a set of images:

  - (strategy one)
  - (strategy two)
  - (strategy three)

Each strategy accepts a set of sub-parameters that define which images to use and what to do with them. The following table contains information about the sub-parameters you can use with each ContainerImagePrepare strategy:



List of image name substrings to exclude from a strategy.


List of image name substrings to include in a strategy. At least one image name must match an existing image. All excludes are ignored if includes is specified.


String to append to the tag for the destination image. For example, if you pull an image with the tag 14.0-89 and set the modify_append_tag to -hotfix, the director tags the final image as 14.0-89-hotfix.


A dictionary of image labels that filter the images to modify. If an image matches the labels defined, the director includes the image in the modification process.


String of ansible role names to run during upload but before pushing the image to the destination registry.


Dictionary of variables to pass to modify_role.


The namespace of the registry to push images during the upload process. When you specify a namespace for this parameter, all image parameters use this namespace too. If set to true, the push_destination is set to the undercloud registry namespace. It is not recommended to set this parameters to false in production environments.


The source registry from where to pull the original container images.


A dictionary of key: value definitions that define where to obtain the initial images.


Defines the label pattern to tag the resulting images. Usually sets to \{version}-\{release}.

The set parameter accepts a set of key: value definitions. The following table contains information about the keys:



The name of the Ceph Storage container image.


The namespace of the Ceph Storage container image.


The tag of the Ceph Storage container image.


A prefix for each OpenStack service image.


A suffix for each OpenStack service image.


The namespace for each OpenStack service image.


The driver to use to determine which OpenStack Networking (neutron) container to use. Use a null value to set to the standard neutron-server container. Set to ovn to use OVN-based containers. Set to odl to use OpenDaylight-based containers.


The tag that the director uses to identify the images to pull from the source registry. You usually keep this key set to latest.


The set section might contains several parameters that begin with openshift_. These parameters are for various scenarios involving OpenShift-on-OpenStack.

2.3. Layering image preparation entries

The value of the ContainerImagePrepare parameter is a YAML list. This means you can specify multiple entries. The following example demonstrates two entries where the director uses the latest version of all images except for the nova-api image, which uses the version tagged with 14.0-44:

- tag_from_label: "{version}-{release}"
  push_destination: true
  - nova-api
    name_prefix: openstack-
    name_suffix: ''
    tag: latest
- push_destination: true
  - nova-api
    tag: 14.0-44

The includes and excludes entries control image filtering for each entry. The images that match the includes strategy take precedence over excludes matches. The image name must include the includes or excludes value to be considered a match.

2.4. Modifying images during preparation

It is possible to modify images during image preparation, then immediately deploy with modified images. Scenarios for modifying images include:

  • As part of a continuous integration pipeline where images are modified with the changes being tested before deployment.
  • As part of a development workflow where local changes need to be deployed for testing and development.
  • When changes need to be deployed but are not available through an image build pipeline. For example, adding proprietry add-ons or emergency fixes.

To modify an image during preparation, invoke an Ansible role on each image that you want to modify. The role takes a source image, makes the requested changes, and tags the result. The prepare command can push the image to the destination registry and set the Heat parameters to refer to the modified image.

The Ansible role tripleo-modify-image conforms with the required role interface, and provides the behaviour necessary for the modify use-cases. Modification is controlled using modify-specific keys in the ContainerImagePrepare parameter:

  • modify_role specifies the Ansible role to invoke for each image to modify.
  • modify_append_tag appends a string to the end of the source image tag. This makes it obvious that the resulting image has been modified. Use this parameter to skip modification if the push_destination registry already contains the modified image. It is recommended to change modify_append_tag whenever you modify the image.
  • modify_vars is a dictionary of Ansible variables to pass to the role.

To select a use-case that the tripleo-modify-image role handles, set the tasks_from variable to the required file in that role.

While developing and testing the ContainerImagePrepare entries that modify images, it is recommended to run the image prepare command without any additional options to confirm the image is modified as expected:

sudo openstack tripleo container image prepare \
  -e ~/containers-prepare-parameter.yaml

2.5. Updating existing packages on container images

The following example ContainerImagePrepare entry updates in all packages on the images using the undercloud host’s yum repository configuration:

- push_destination: true
  modify_role: tripleo-modify-image
  modify_append_tag: "-updated"
    tasks_from: yum_update.yml
    compare_host_packages: true
    yum_repos_dir_path: /etc/yum.repos.d

2.6. Installing additional RPM files to container images

You can install a directory of RPM files in your container images. This is useful for installing hotfixes, local package builds, or any package not available through a package repository. For example, the following ContainerImagePrepare entry installs some hotfix packages only on the nova-compute image:

- push_destination: true
  - nova-compute
  modify_role: tripleo-modify-image
  modify_append_tag: "-hotfix"
    tasks_from: rpm_install.yml
    rpms_path: /home/stack/nova-hotfix-pkgs

2.7. Modifying container images with a custom Dockerfile

For maximum flexibility, you can specify a directory containing a Dockerfile to make the required changes. When you invoke the tripleo-modify-image role, the role generates a Dockerfile.modified file that changes the FROM directive and adds extra LABEL directives. The following example runs the custom Dockerfile on the nova-compute image:

- push_destination: true
  - nova-compute
  modify_role: tripleo-modify-image
  modify_append_tag: "-hotfix"
    tasks_from: modify_image.yml
    modify_dir_path: /home/stack/nova-custom

An example /home/stack/nova-custom/Dockerfile` follows. After running any USER root directives, you must switch back to the original image default user:


USER "root"

COPY /tmp/
RUN /tmp/

USER "nova"

2.8. Preparing a Satellite server for container images

Red Hat Satellite 6 offers registry synchronization capabilities. This provides a method to pull multiple images into a Satellite server and manage them as part of an application life cycle. The Satellite also acts as a registry for other container-enabled systems to use. For more details information on managing container images, see "Managing Container Images" in the Red Hat Satellite 6 Content Management Guide.

The examples in this procedure use the hammer command line tool for Red Hat Satellite 6 and an example organization called ACME. Substitute this organization for your own Satellite 6 organization.


  1. Create a list of all container images, including the Ceph images:

    $ sudo docker search "" | awk '{ print $2 }' | grep -v beta | sed "s/\///g" | tail -n+2 > satellite_images
    $ echo "rhceph/rhceph-3-rhel7" >> satellite_images_names
  2. Copy the satellite_images_names file to a system that contains the Satellite 6 hammer tool. Alternatively, use the instructions in the Hammer CLI Guide to install the hammer tool to the undercloud.
  3. Run the following hammer command to create a new product (OSP14 Containers) in your Satellite organization:

    $ hammer product create \
      --organization "ACME" \
      --name "OSP14 Containers"

    This custom product will contain our images.

  4. Add the base container image to the product:

    $ hammer repository create \
      --organization "ACME" \
      --product "OSP14 Containers" \
      --content-type docker \
      --url \
      --docker-upstream-name rhosp14/openstack-base \
      --name base
  5. Add the overcloud container images from the satellite_images file.

    $ while read IMAGE; do \
      IMAGENAME=$(echo $IMAGE | cut -d"/" -f2 | sed "s/openstack-//g" | sed "s/:.*//g") ; \
      hammer repository create \
      --organization "ACME" \
      --product "OSP14 Containers" \
      --content-type docker \
      --url \
      --docker-upstream-name $IMAGE \
      --name $IMAGENAME ; done < satellite_images_names
  6. Synchronize the container images:

    $ hammer product synchronize \
      --organization "ACME" \
      --name "OSP14 Containers"

    Wait for the Satellite server to complete synchronization.


    Depending on your configuration, hammer might ask for your Satellite server username and password. You can configure hammer to automatically login using a configuration file. For more information, see the "Authentication" section in the Hammer CLI Guide.

  7. If your Satellite 6 server uses content views, create a new content view version to incorporate the images and promote it along environments in your application life cycle. This largely depends on how you structure your application lifecycle. For example, if you have an environment called production in your lifecycle and you want the container images available in that environment, create a content view that includes the container images and promote that content view to the production environment. For more information, see "Managing Container Images with Content Views".
  8. Check the available tags for the base image:

    $ hammer docker tag list --repository "base" \
      --organization "ACME" \
      --environment "production" \
      --content-view "myosp14" \
      --product "OSP14 Containers"

    This command displays tags for the OpenStack Platform container images within a content view for an particular environment.

  9. Return to the undercloud and generate a default environment file for preparing images using your Satellite server as a source. Run the following example command to generate the environment file:

    (undercloud) $ openstack tripleo container image prepare default \
      --output-env-file containers-prepare-parameter.yaml
    • --output-env-file is an environment file name. The contents of this file will include the parameters for preparing your container images for the undercloud. In this case, the name of the file is containers-prepare-parameter.yaml.
  10. Edit the containers-prepare-parameter.yaml file and modify the following parameters:

    • namespace - The URL and port of the registry on the Satellite server. The default registry port on Red Hat Satellite is 5000.
    • name_prefix - The prefix is based on a Satellite 6 convention. This differs depending on whether you use content views:

      • If you use content views, the structure is [org]-[environment]-[content view]-[product]-. For example: acme-production-myosp14-osp14_containers-.
      • If you do not use content views, the structure is [org]-[product]-. For example: acme-osp14_containers-.
    • ceph_namespace, ceph_image, ceph_tag - If using Ceph Storage, include the additional parameters to define the Ceph Storage container image location. Note that ceph_image now includes a Satellite-specific prefix. This prefix is the same value as the name_prefix option.

The following example environment file contains Satellite-specific parameters:

  - push_destination: true
      ceph_image: acme-production-myosp14-osp14_containers-rhceph-3-rhel7
      ceph_tag: latest
      name_prefix: acme-production-myosp14-osp14_containers-
      name_suffix: ''
      neutron_driver: null
      tag: latest
    tag_from_label: '{version}-{release}'

Use this environment file when creating both your undercloud and overcloud.

Chapter 3. Installing the undercloud with containers

This chapter provides info on how to create a container-based undercloud and keep it updated.

3.1. Configuring the director

The director installation process requires certain settings in the undercloud.conf configuration file, which the director reads from the stack user’s home directory. This procedure demonstrates how to use the default template as a foundation for your configuration.


  1. Copy the default template to the stack user’s home directory:

    [stack@director ~]$ cp \
      /usr/share/python-tripleoclient/undercloud.conf.sample \
  2. Edit the undercloud.conf file. This file contains settings to configure your undercloud. If you omit or comment out a parameter, the undercloud installation uses the default value.

3.2. Director configuration parameters

The following list contains information about parameters for configuring the undercloud.conf file. Keep all parameters within their relevant sections to avoid errors.


The following parameters are defined in the [DEFAULT] section of the undercloud.conf file:


A list of additional (kernel) architectures that an overcloud supports. Currently the overcloud supports ppc64le architecture.


When enabling support for ppc64le, you must also set ipxe_enabled to False

The certmonger nickname of the CA that signs the requested certificate. Use this option only if you have set the generate_service_certificate parameter. If you select the local CA, certmonger extracts the local CA certificate to /etc/pki/ca-trust/source/anchors/cm-local-ca.pem and adds the certificate to the trust chain.
Defines whether to wipe the hard drive between deployments and after introspection.
Cleanup temporary files. Set this to False to leave the temporary files used during deployment in place after the command is run. This is useful for debugging the generated files or if errors occur.

Heat environment file with container image information. This can either be:

  • Parameters for all required container images
  • Or the ContainerImagePrepare parameter to drive the required image preparation. Usually the file containing this parameter is named containers-prepare-parameter.yaml.
Additional environment file to add to the undercloud installation.
The user installing the undercloud. Leave this parameter unset to use the current default user (stack).
Sets the default driver for automatically enrolled nodes. Requires enable_node_discovery enabled and you must include the driver in the enabled_hardware_types list.
A list of insecure registries for docker to use. Use this parameter if you want to pull images from another source, such as a private container registry. In most cases, docker has the certificates to pull container images from either the Red Hat Container Catalog or from your Satellite server if the undercloud is registered to Satellite.
An optional registry-mirror configured in /etc/docker/daemon.json
enable_ironic; enable_ironic_inspector; enable_mistral; enable_tempest; enable_validations; enable_zaqar
Defines the core services to enable for director. Leave these parameters set to true.
Defines whether to install the director web UI. Use this parameter to perform overcloud planning and deployments through a graphical web interface. Note that the UI is only available with SSL/TLS enabled using either the undercloud_service_certificate or generate_service_certificate.
Automatically enroll any unknown node that PXE-boots the introspection ramdisk. New nodes use the fake_pxe driver as a default but you can set discovery_default_driver to override. You can also use introspection rules to specify driver information for newly enrolled nodes.
Defines whether to install the novajoin metadata service in the Undercloud.
Defines whether to enable support for routed control plane networks.
Defines whether to enable Swift encryption at-rest.
Defines whether to install OpenStack Telemetry services (gnocchi, aodh, panko) in the undercloud. Set enable_telemetry parameter to true if you want to install and configure telemetry services automatically. The default value is false, which disables telemetry on the undercloud. This parameter is required if using other products that consume metrics data, such as Red Hat CloudForms.
A list of hardware types to enable for the undercloud.
Defines whether to generate an SSL/TLS certificate during the undercloud installation, which is used for the undercloud_service_certificate parameter. The undercloud installation saves the resulting certificate /etc/pki/tls/certs/undercloud-[undercloud_public_vip].pem. The CA defined in the certificate_generation_ca parameter signs this certificate.
URL for the heat container image to use. Leave unset.
Use native heat templates. Leave as true.
Path to hieradata override file that configures Puppet hieradata on the director, providing custom configuration to services beyond the undercloud.conf parameters. If set, the undercloud installation copies this file to the /etc/puppet/hieradata directory and sets it as the first file in the hierarchy. See Configuring hieradata on the undercloud for details on using this feature.
Defines whether to enable extra hardware collection during the inspection process. This parameter requires python-hardware or python-hardware-detect package on the introspection image.
The bridge the director uses for node introspection. This is a custom bridge that the director configuration creates. The LOCAL_INTERFACE attaches to this bridge. Leave this as the default br-ctlplane.
Runs a set of benchmarks during node introspection. Set this parameter to true to enable the benchmarks. This option is necessary if you intend to perform benchmark analysis when inspecting the hardware of registered nodes.
Defines the one time password to register the Undercloud node to an IPA server. This is required when enable_novajoin is enabled.
Defines whether to use iPXE or standard PXE. The default is true, which enables iPXE. Set to false to set to standard PXE.

The chosen interface for the director’s Provisioning NIC. This is also the device the director uses for DHCP and PXE boot services. Change this value to your chosen device. To see which device is connected, use the ip addr command. For example, this is the result of an ip addr command:

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 52:54:00:75:24:09 brd ff:ff:ff:ff:ff:ff
    inet brd scope global dynamic eth0
       valid_lft 3462sec preferred_lft 3462sec
    inet6 fe80::5054:ff:fe75:2409/64 scope link
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noop state DOWN
    link/ether 42:0b:c2:a5:c1:26 brd ff:ff:ff:ff:ff:ff

In this example, the External NIC uses eth0 and the Provisioning NIC uses eth1, which is currently not configured. In this case, set the local_interface to eth1. The configuration script attaches this interface to a custom bridge defined with the inspection_interface parameter.

The IP address defined for the director’s Provisioning NIC. This is also the IP address that the director uses for DHCP and PXE boot services. Leave this value as the default unless you use a different subnet for the Provisioning network, for example, if it conflicts with an existing IP address or subnet in your environment.
MTU to use for the local_interface. Do not exceed 1500 for the undercloud.
The local subnet to use for PXE boot and DHCP interfaces. The local_ip address should reside in this subnet. The default is ctlplane-subnet.
Path to network configuration override template. If you set this parameter, the undercloud uses a JSON format template to configure the networking with os-net-config. The undercloud ignores the network parameters set in undercloud.conf. See /usr/share/python-tripleoclient/undercloud.conf.sample for an example.
Directory to output state, processed heat templates, and Ansible deployment files.

The DNS domain name to use when deploying the overcloud.


When configuring the overcloud, the CloudDomain parameter must be set to a matching value. Set this parameter in an environment file when you configure your overcloud.

The roles file to override for undercloud installation. It is highly recommended to leave unset so that the director installation uses the default roles file.
Maximum number of times the scheduler attempts to deploy an instance. This value must be greater or equal to the number of bare metal nodes that you expect to deploy at once to work around potential race condition when scheduling.
The Kerberos principal for the service using the certificate. Use this parameter only if your CA requires a Kerberos principal, such as in FreeIPA.
List of routed network subnets for provisioning and introspection. See Subnets for more information. The default value includes only the ctlplane-subnet subnet.
Heat templates file to override.
The IP address defined for the director Admin API when using SSL/TLS. This is an IP address for administration endpoint access over SSL/TLS. The director configuration attaches the director’s IP address to its software bridge as a routed IP address, which uses the /32 netmask.
Sets the log level of undercloud services to DEBUG. Set this value to true to enable.
Enable or disable SELinux during the deployment. It is highly recommended to leave this value set to true unless you are debugging an issue.
Defines the fully qualified host name for the undercloud. If set, the undercloud installation configures all system host name settings. If left unset, the undercloud uses the current host name, but the user must configure all system host name settings appropriately.
The path to a log file to store the undercloud install/upgrade logs. By default, the log file is install-undercloud.log within the home directory. For example, /home/stack/install-undercloud.log.
A list of DNS nameservers to use for the undercloud hostname resolution.
A list of network time protocol servers to help synchronize the undercloud date and time.
The IP address defined for the director Public API when using SSL/TLS. This is an IP address for accessing the director endpoints externally over SSL/TLS. The director configuration attaches this IP address to the director software bridge as a routed IP address, which uses the /32 netmask.
The location and filename of the certificate for OpenStack SSL/TLS communication. Ideally, you obtain this certificate from a trusted certificate authority. Otherwise, generate your own self-signed certificate.
Defines whether to update packages during the undercloud installation.


Each provisioning subnet is a named section in the undercloud.conf file. For example, to create a subnet called ctlplane-subnet, use the following sample in your undercloud.conf file:

cidr =
dhcp_start =
dhcp_end =
inspection_iprange =,
gateway =
masquerade = true

You can specify as many provisioning networks as necessary to suit your environment.

The gateway for the overcloud instances. This is the undercloud host, which forwards traffic to the External network. Leave this as the default unless you use a different IP address for the director or want to use an external gateway directly.

The director configuration also enables IP forwarding automatically using the relevant sysctl kernel parameter.

The network that the director uses to manage overcloud instances. This is the Provisioning network, which the undercloud neutron service manages. Leave this as the default unless you use a different subnet for the Provisioning network.
Defines whether to masquerade the network defined in the cidr for external access. This provides the Provisioning network with a degree of network address translation (NAT) so that the Provisioning network has external access through the director.
dhcp_start; dhcp_end
The start and end of the DHCP allocation range for overcloud nodes. Ensure this range contains enough IP addresses to allocate your nodes.

Modify the values for these parameters to suit your configuration. When complete, save the file.

3.3. Installing the director

Complete the following procedure to install the director and perform some basic post-installation tasks.


  1. Run the following command to install the director on the undercloud:

    [stack@director ~]$ openstack undercloud install

    This launches the director’s configuration script. The director installs additional packages and configures its services according to the configuration in the undercloud.conf. This script takes several minutes to complete.

    The script generates two files when complete:

    • undercloud-passwords.conf - A list of all passwords for the director’s services.
    • stackrc - A set of initialization variables to help you access the director’s command line tools.
  2. The script also starts all OpenStack Platform service containers automatically. Check the enabled containers using the following command:

    [stack@director ~]$ sudo docker ps
  3. The script adds the stack user to the docker group to give the stack user access to container management commands. Refresh the stack user’s permissions with the following command:

    [stack@director ~]$ exec su -l stack

    The command prompts you to log in again. Enter the stack user’s password.

  4. To initialize the stack user to use the command line tools, run the following command:

    [stack@director ~]$ source ~/stackrc

    The prompt now indicates OpenStack commands authenticate and execute against the undercloud;

    (undercloud) [stack@director ~]$

The director installation is complete. You can now use the director’s command line tools.

3.4. Performing a minor update of a containerized undercloud

The director provides commands to update the packages on the undercloud node. This allows you to perform a minor update within the current version of your OpenStack Platform environment.


  1. Log into the director as the stack user.
  2. Run yum to upgrade the director’s main packages:

    $ sudo yum update -y python-tripleoclient* openstack-tripleo-common openstack-tripleo-heat-templates
  3. The director uses the openstack undercloud upgrade command to update the undercloud environment. Run the command:

    $ openstack undercloud upgrade
  4. Wait until the undercloud upgrade process completes.
  5. Reboot the undercloud to update the operating system’s kernel and other system packages:

    $ sudo reboot
  6. Wait until the node boots.

Chapter 4. Deploying and updating an overcloud with containers

This chapter provides info on how to create a container-based overcloud and keep it updated.

4.1. Deploying an overcloud

This procedure demonstrates how to deploy an overcloud with minimum configuration. The result will be a basic two-node overcloud (1 Controller node, 1 Compute node).


  1. Source the stackrc file:

    $ source ~/stackrc
  2. Run the deploy command and include the file containing your overcloud image locations (usually overcloud_images.yaml):

    (undercloud) $ openstack overcloud deploy --templates \
      -e /home/stack/templates/overcloud_images.yaml \
  3. Wait until the overcloud completes deployment.

4.2. Updating an overcloud

For information on updating a containerized overcloud, see the Keeping Red Hat OpenStack Platform Updated guide.

Chapter 5. Working with containerized services

This chapter provides some examples of commands to manage containers and how to troubleshoot your OpenStack Platform containers

5.1. Managing containerized services

OpenStack Platform runs services in containers on the undercloud and overcloud nodes. In certain situations, you might need to control the individual services on a host. This section contains information about some common docker commands you can run on a node to manage containerized services. For more comprehensive information about using docker to manage containers, see "Working with Docker formatted containers" in the Getting Started with Containers guide.

Listing containers and images

To list running containers, run the following command:

$ sudo docker ps

To include stopped or failed containers in the command output, add the --all option to the command:

$ sudo docker ps --all

To list container images, run the following command:

$ sudo docker images

Inspecting container properties

To view the properties of a container or container images, use the docker inspect command. For example, to inspect the keystone container, run the following command:

$ sudo docker inspect keystone

Managing basic container operations

To restart a containerized service, use the docker restart command. For example, to restart the keystone container, run the following command:

$ sudo docker restart keystone

To stop a containerized service, use the docker stop command. For example, to stop the keystone container, run the following command:

$ sudo docker stop keystone

To start a stopped containerized service, use the docker start command. For example, to start the keystone container, run the following command:

$ sudo docker start keystone

Any changes to the service configuration files within the container revert after restarting the container. This is because the container regenerates the service configuration based on files on the node’s local file system in /var/lib/config-data/puppet-generated/. For example, if you edit /etc/keystone/keystone.conf within the keystone container and restart the container, the container regenerates the configuration using /var/lib/config-data/puppet-generated/keystone/etc/keystone/keystone.conf on the node’s local file system, which overwrites any the changes made within the container before the restart.

Monitoring containers

To check the logs for a containerized service, use the docker logs command. For example, to view the logs for the keystone container, run the following command:

$ sudo docker logs keystone

Accessing containers

To enter the shell for a containerized service, use the docker exec command to launch /bin/bash. For example, to enter the shell for the keystone container, run the following command:

$ sudo docker exec -it keystone /bin/bash

To enter the shell for the keystone container as the root user, run the following command:

$ sudo docker exec --user 0 -it <NAME OR ID> /bin/bash

To exit from the container, run the following command:

# exit

Enabling swift-ring-builder on undercloud and overcloud

For continuity considerations in Object Storage (swift) builds, the swift-ring-builder and swift_object_server commands are no longer packaged on the undercloud or overcloud nodes. However, the commands are still available in the containers. To run them inside the respective containers:

docker exec -ti -u swift swift_object_server swift-ring-builder /etc/swift/object.builder

If you require these commands, install the following package as the stack user on the undercloud or the heat-admin user on the overcloud:

sudo yum install -y python-swift
sudo yum install -y python2-swiftclient

5.2. Troubleshooting containerized services

If a containerized service fails during or after overcloud deployment, use the following recommendations to determine the root cause for the failure:


Before running these commands, check that you are logged into an overcloud node and not running these commands on the undercloud.

Checking the container logs

Each container retains standard output from its main process. This output acts as a log to help determine what actually occurs during a container run. For example, to view the log for the keystone container, use the following command:

$ sudo docker logs keystone

In most cases, this log provides the cause of a container’s failure.

Inspecting the container

In some situations, you might need to verify information about a container. For example, use the following command to view keystone container data:

$ sudo docker inspect keystone

This provides a JSON object containing low-level configuration data. You can pipe the output to the jq command to parse specific data. For example, to view the container mounts for the keystone container, run the following command:

$ sudo docker inspect keystone | jq .[0].Mounts

You can also use the --format option to parse data to a single line, which is useful for running commands against sets of container data. For example, to recreate the options used to run the keystone container, use the following inspect command with the --format option:

$ sudo docker inspect --format='{{range .Config.Env}} -e "{{.}}" {{end}} {{range .Mounts}} -v {{.Source}}:{{.Destination}}{{if .Mode}}:{{.Mode}}{{end}}{{end}} -ti {{.Config.Image}}' keystone

The --format option uses Go syntax to create queries.

Use these options in conjunction with the docker run command to recreate the container for troubleshooting purposes:

$ OPTIONS=$( sudo docker inspect --format='{{range .Config.Env}} -e "{{.}}" {{end}} {{range .Mounts}} -v {{.Source}}:{{.Destination}}{{if .Mode}}:{{.Mode}}{{end}}{{end}} -ti {{.Config.Image}}' keystone )
$ sudo docker run --rm $OPTIONS /bin/bash

Running commands in the container

In some cases, you might need to obtain information from within a container through a specific Bash command. In this situation, use the following docker command to execute commands within a running container. For example, to run a command in the keystone container:

$ sudo docker exec -ti keystone <COMMAND>

The -ti options run the command through an interactive pseudoterminal.

Replace <COMMAND> with your desired command. For example, each container has a health check script to verify the service connection. You can run the health check script for keystone with the following command:

$ sudo docker exec -ti keystone /openstack/healthcheck

To access the container’s shell, run docker exec using /bin/bash as the command:

$ sudo docker exec -ti keystone /bin/bash

Exporting a container

When a container fails, you might need to investigate the full contents of the file. In this case, you can export the full file system of a container as a tar archive. For example, to export the keystone container’s file system, run the following command:

$ sudo docker export keystone -o keystone.tar

This command create the keystone.tar archive, which you can extract and explore.

Chapter 6. Comparing Systemd services to containerized services

This chapter provides some reference material to show how containerized services differ from Systemd services.

6.1. Systemd service commands vs containerized service commands

The following table shows some similarities between Systemd-based commands and their Docker equivalents. This helps identify the type of service operation you aim to perform.


List all services

systemctl list-units -t service

docker ps --all

List active services

systemctl list-units -t service --state active

docker ps

Check status of service

systemctl status openstack-nova-api

docker ps --filter "name=nova_api$" --all

Stop service

systemctl stop openstack-nova-api

docker stop nova_api

Start service

systemctl start openstack-nova-api

docker start nova_api

Restart service

systemctl restart openstack-nova-api

docker restart nova_api

Show service configuration

systemctl show openstack-nova-api

systemctl cat openstack-nova-api

docker inspect nova_api

Show service logs

journalctl -u openstack-nova-api

docker logs nova_api

6.2. Systemd services vs containerized services

The following table shows Systemd-based OpenStack services and their container-based equivalents.

OpenStack serviceSystemd servicesDocker containers





httpd (openstack-aodh-api)









httpd (openstack-ceilometer-api)

















httpd (openstack-gnocchi-api)













httpd (openstack-dashboard)



httpd (openstack-keystone)




























































6.3. Systemd log locations vs containerized log locations

The following table shows Systemd-based OpenStack logs and their equivalents for containers. All container-based log locations are available on the physical host and are mounted to the container.

OpenStack serviceSystemd service logsDocker container logs



























































6.4. Systemd configuration vs containerized configuration

The following table shows Systemd-based OpenStack configuration and their equivalents for containers. All container-based configuration locations are available on the physical host, are mounted to the container, and are merged (via kolla) into the configuration within each respective container.

OpenStack serviceSystemd service configurationDocker container configuration
























































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