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.

iSCSI deploy

With iscsi deploy interface, the deploy ramdisk publishes the node’s hard drive as an iSCSI share. The ironic-conductor then copies the image to this share. See iSCSI deploy diagram for a detailed explanation of how this deploy interface works.

This interface is used by default, if enabled (see Enabling hardware interfaces). You can specify it explicitly when creating or updating a node:

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

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:

openstack baremetal node create --driver ipmi --deploy-interface direct
openstack 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
...

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

Each HTTP servers 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.

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 = iscsi,direct,ansible
...

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

openstack baremetal node create --driver ipmi --deploy-interface ansible
openstack 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.

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. Most commonly this is performed when an instance is booted via PXE, iPXE or Virtual Media, with the only local storage contents being those in memory. It is suported by pxe and ilo-virtual-media boot interfaces.

As with most non-default interfaces, it must be enabled and set for a node to be utilized:

[DEFAULT]
...
enabled_deploy_interfaces = iscsi,direct,ramdisk
...

Once enabled and the conductor(s) have been restarted, the interface can be set upon creation of a new node or update a pre-existing node:

openstack baremetal node create --driver ipmi \
    --deploy-interface ramdisk \
    --boot-interface pxe
openstack baremetal node set <NODE> --deploy-interface ramdisk

The intended use case is for advanced scientific and ephemeral workloads where the step of writing an image to the local storage is not required or desired. As such, this interface does come with several caveats:

  • Configuration drives are not supported.

  • Disk image contents are not written to the bare metal node.

  • Users and Operators who intend to leverage this interface should expect to leverage a metadata service, custom ramdisk images, or the instance_info/ramdisk_kernel_arguments parameter to add options to the kernel boot command line.

  • Bare metal nodes must continue to have network access to PXE and iPXE network resources. This is contrary to most tenant networking enabled configurations where this access is restricted to the provisioning and cleaning networks

  • As with all deployment interfaces, automatic cleaning of the node will still occur with the contents of any local storage being wiped between deployments.