Deploy Interfaces

A deploy interface plays a critical role in the provisioning process. It orchestrates the whole deployment and defines how the image gets transferred to the target disk.

Direct deploy

With direct deploy interface, the deploy ramdisk fetches the image from an HTTP location. It can be an object storage (swift or RadosGW) temporary URL or a user-provided HTTP URL. The deploy ramdisk then copies the image to the target disk. See direct deploy diagram for a detailed explanation of how this deploy interface works.

You can specify this deploy interface when creating or updating a node:

baremetal node create --driver ipmi --deploy-interface direct
baremetal node set <NODE> --deploy-interface direct

Note

For historical reasons the direct deploy interface is sometimes called agent. This is because before the Kilo release ironic-python-agent used to only support this deploy interface.

Deploy with custom HTTP servers

The direct deploy interface can also be configured to use with custom HTTP servers set up at ironic conductor nodes, images will be cached locally and made accessible by the HTTP server.

To use this deploy interface with a custom HTTP server, set image_download_source to http in the [agent] section.

[agent]
...
image_download_source = http
...

This configuration affects glance and file:// images. If you want http(s):// images to also be cached and served locally, use instead:

[agent]
image_download_source = local

Note

This option can also be set per node in driver_info:

baremetal node set <node> --driver-info image_download_source=local

or per instance in instance_info:

baremetal node set <node> --instance-info image_download_source=local

You need to set up a workable HTTP server at each conductor node which with direct deploy interface enabled, and check http related options in the ironic configuration file to match the HTTP server configurations.

[deploy]
http_url = http://example.com
http_root = /httpboot

Note

See also: Deploying outside of the provisioning network.

Each HTTP server should be configured to follow symlinks for images accessible from HTTP service. Please refer to configuration option FollowSymLinks if you are using Apache HTTP server, or disable_symlinks if Nginx HTTP server is in use.

Streaming raw images

The Bare Metal service is capable of streaming raw images directly to the target disk of a node, without caching them in the node’s RAM. When the source image is not already raw, the conductor will convert the image and calculate the new checksum.

Note

If no algorithm is specified via the image_os_hash_algo field, or if this field is set to md5, SHA256 is used for the updated checksum.

For HTTP or local file images that are already raw, you need to explicitly set the disk format to prevent the checksum from being unnecessarily re-calculated. For example:

baremetal node set <node> \
    --instance-info image_source=http://server/myimage.img \
    --instance-info image_os_hash_algo=sha512 \
    --instance-info image_os_hash_value=<SHA512 of the raw image> \
    --instance-info image_disk_format=raw

To disable this feature and cache images in the node’s RAM, set

[agent]
stream_raw_images = False

To disable the conductor-side conversion completely, set

[DEFAULT]
force_raw_images = False

Ansible deploy

This interface is similar to direct in the sense that the image is downloaded by the ramdisk directly from the image store (not from ironic-conductor host), but the logic of provisioning the node is held in a set of Ansible playbooks that are applied by the ironic-conductor service handling the node. While somewhat more complex to set up, this deploy interface provides greater flexibility in terms of advanced node preparation during provisioning.

This interface is supported by most but not all hardware types declared in ironic. However this deploy interface is not enabled by default. To enable it, add ansible to the list of enabled deploy interfaces in enabled_deploy_interfaces option in the [DEFAULT] section of ironic’s configuration file:

[DEFAULT]
...
enabled_deploy_interfaces = direct,ansible
...

Once enabled, you can specify this deploy interface when creating or updating a node:

baremetal node create --driver ipmi --deploy-interface ansible
baremetal node set <NODE> --deploy-interface ansible

For more information about this deploy interface, its features and how to use it, see Ansible deploy interface.

Anaconda deploy

The anaconda deploy interface is another option for highly customized deployments. See Deploying with anaconda deploy interface for more details.

Ramdisk deploy

The ramdisk interface is intended to provide a mechanism to “deploy” an instance where the item to be deployed is in reality a ramdisk. It is documented separately, see Booting a Ramdisk or an ISO.

Custom agent deploy

The custom-agent deploy interface is designed for operators who want to completely orchestrate writing the instance image using in-band deploy steps from a custom agent image. If you use this deploy interface, you are responsible to provide all necessary deploy steps with priorities between 61 and 99 (see Agent steps for information on priorities).

Bootc Agent Deploy

The bootc deploy interface is designed to enable operators to deploy containers directly from a container image registry without intermediate conversion steps, such as creating custom disk images for modifications. This deployment interface utilizes the bootc project.

Ultimately this enables a streamlined flow, where a user of the deployment interface can create updated containers rapidly and the deployment interface will deploy that container image in a streamlined fashion without the need to create intermediate disk images and post the disk images in a location where they can be accessed for deployment.

Ultimately this interface enables a streamlined flow, and offers limited flexibility in the model of deployment. As a result, this interface consumes the entire target disk on the host being deployed and offers no customization in terms of partitioning. This is largely because the overall security model of a bootc deployment, which leverages os-tree, is also fundamentally different than the model to leverage partition separation.

Note

This interface should be considered experimental and may evolve to include additional features as the Ironic project maintainers receive additional feedback.

Note

This interface is dependent upon the existence of bootc within a container image along with sufficient memory on the baremetal node being deployed to enable a complete download and extraction of image contents within system memory. It is this memory constraint which is why this interface is not actively tested in upstream CI. The possible failure modes of this interface are mainly focused upon the ability of the ramdisk being able to download, launch, and run bootc to trigger the installation which also isolates most risk to the actual bootc process execution.

Features

While this deploy_interface supports deploying configuration drives like most other Ironic supplied deploy interfaces, some additional parameters can be supplied via instance_info to enable tuning of deploy-time behavior by the user which cannot be modified post-deployment.

• bootc_authorized_keys - This option allows injection of a root user authorized keys file which is preserved inside of the deployed container on the host. This option is for actual key file content and can be one or more keys with a new line character.

• bootc_tpm2_luks - A boolean option, default False, enabling bootc to attempt to utilize auto-encryption of the deployed host filesystem upon which the container is deployed. This is not enabled by default due to a lack of software TPMs in Ironic CI. If operators would like this setting default changed, please discuss with Ironic developers.

Additionally, this interface also supports the passing of a pull secret to enable download from the remote image registry, which is part of the support for retrieval of artifacts from OCI Container registires. This parameter is image_pull_secret.

Caveats

• This deployment interface was not designed to be compatible with the OpenStack Compute service. This is because OpenStack focuses on disk images from Glance as to what to deploy, where as this interface is modeled to utilize a container image registry.

• Performance wise, this deployment interface performs many smaller actions, which at some times need to performed in a specific sequence, such as when unpacking layers. As a result, when comparing similar size containers to disk images, this interface is slower than the direct deploy interface.

• Container Images must have the bootc command present along with the applicable bootloader and artifacts required for whatever platform is being deployed.

• Because of how bootc works, there is no concept of “image streaming” directly to disk. This is because the way this interface works, podman is used to download all container image layer artifacts, along with extracting the layers. At which point bootc is executed and it begins to setup the disk for the host. As a result, most of the time a deploy is in progress will be observable as deploy wait while bootc executes.

• The memory requirements of the ramdisk, due to the way this interface works, requires the ability to download a container image, copy, and ultimatley extract all layers into the in-memory filesystem. Due to the way the kernel launches and allocates ramdisk memory for filesystem usage, a 600MB container image may require upwards of 10GB of RAM to be available on the overall host.

• This deployment interface explicitly signals to bootc that it should not execute it’s internal post-deployment “fetch check” to ensure upgrades are working. This is because this action may require authentication to succeed, and thus require credentials in the container to work. Configuration of credentials for day-2 operations such as the execution of bootc upgrade, must be addressed post-deployment.

• If you intend SELinux to be enabled on the deployed host, it must also be enabled inside of the ironic-python-agent ramdisk. This is a design limitation of bootc outside of Ironic’s control.

Limitations

• At present, this interface does not support use of caching proxies. This may be addressed in the future.

• This deployment interface directly downloads artifacts from the requested Container Registry. Caching the container artifacts on the ironic-conductor host is not available. If you need the contaitainer content localized to the conductor, consider utilizing your own container registry.