Node Deployment

Overview

Node deployment is performed by the Bare Metal service to prepare a node for use by a workload. The exact work flow used depends on a number of factors, including the hardware type and interfaces assigned to a node.

Deploy Steps

The Bare Metal service implements deployment by collecting a list of deploy steps to perform on a node from the Power, Deploy, Management, BIOS, and RAID interfaces of the driver assigned to the node. These steps are then ordered by priority and executed on the node when the node is moved to the deploying state.

Nodes move to the deploying state when attempting to move to the active state (when the hardware is prepared for use by a workload). For a full understanding of all state transitions into deployment, please see Ironic’s State Machine.

The Bare Metal service added support for deploy steps in the Rocky release.

Order of execution

Deploy steps are ordered from higher to lower priority, where a larger integer is a higher priority. If the same priority is used by deploy steps on different interfaces, the following resolution order is used: Power, Management, Deploy, BIOS, and RAID interfaces.

Agent steps

All deploy interfaces based on ironic-python-agent (i.e. direct, iscsi and ansible and any derivatives) expose the following deploy steps:

deploy.deploy (priority 100)

In this step the node is booted using a provisioning image.

deploy.write_image (priority 80)

An out-of-band (iscsi, ansible) or in-band (direct) step that downloads and writes the image to the node.

deploy.tear_down_agent (priority 40)

In this step the provisioning image is shut down.

deploy.switch_to_tenant_network (priority 30)

In this step networking for the node is switched from provisioning to tenant networks.

deploy.boot_instance (priority 20)

In this step the node is booted into the user image.

Additionally, the iscsi and direct deploy interfaces have:

deploy.prepare_instance_boot (priority 60)

In this step the boot device is configured and the bootloader is installed.

Note

For the ansible deploy interface these steps are done in deploy.write_image.

Accordingly, the following priority ranges can be used for custom deploy steps:

> 100

Out-of-band steps to run before deployment.

81 to 99

In-band deploy steps to run before the image is written.

61 to 79

In-band deploy steps to run after the image is written but before the bootloader is installed.

41 to 59

In-band steps to run after the image is written the bootloader is installed.

21 to 39

Out-of-band steps to run after the provisioning image is shut down.

1 to 19

Any steps that are run when the user instance is already running.

In-band steps

More deploy steps can be provided by the ramdisk, see IPA hardware managers documentation for a listing.

Writing a Deploy Step

Please refer to Developing a new Deploy Step.

FAQ

What deploy step is running?

To check what deploy step the node is performing or attempted to perform and failed, run the following command; it will return the value in the node’s driver_internal_info field:

baremetal node show $node_ident -f value -c driver_internal_info

The deploy_steps field will contain a list of all remaining steps with their priorities, and the first one listed is the step currently in progress or that the node failed before going into deploy failed state.

Troubleshooting

If deployment fails on a node, the node will be put into the deploy failed state until the node is deprovisioned. A deprovisioned node is moved to the available state after the cleaning process has been performed successfully.

Strategies for determining why a deploy step failed include checking the ironic conductor logs, checking logs from the ironic-python-agent that have been stored on the ironic conductor, or performing general hardware troubleshooting on the node.

Deploy Templates

Starting with the Stein release, with Bare Metal API version 1.55, deploy templates offer a way to define a set of one or more deploy steps to be executed with particular sets of arguments and priorities.

Each deploy template has a name, which must be a valid trait. Traits can be either standard or custom. Standard traits are listed in the os_traits library. Custom traits must meet the following requirements:

  • prefixed with CUSTOM_

  • contain only upper case characters A to Z, digits 0 to 9, or underscores

  • no longer than 255 characters in length

Deploy step format

An invocation of a deploy step is defined in a deploy template as follows:

{
    "interface": "<name of the driver interface>",
    "step": "<name of the step>",
    "args": {
        "<arg1>": "<value1>",
        "<arg2>": "<value2>"
    },
    "priority": <priority of the step>
}

A deploy template contains a list of one or more such steps. Each combination of interface and step may only be specified once in a deploy template.

Matching deploy templates

During deployment, if any of the traits in a node’s instance_info.traits field match the name of a deploy template, then the steps from that deploy template will be added to the list of steps to be executed by the node.

When using the Compute service, any traits in the instance’s flavor properties or image properties are stored in instance_info.traits during deployment. See Scheduling based on traits for further information on how traits are used for scheduling when the Bare Metal service is used with the Compute service.

Note that there is no ongoing relationship between a node and any templates that are matched during deployment. The set of matching deploy templates is checked at deployment time. Any subsequent updates to or deletion of those templates will not be reflected in the node’s configuration unless it is redeployed or rebuilt. Similarly, if a node is rebuilt and the set of matching deploy templates has changed since the initial deployment, then the resulting configuration of the node may be different from the initial deployment.

Overriding default deploy steps

A deploy step is enabled by default if it has a non-zero default priority. A default deploy step may be overridden in a deploy template. If the step’s priority is a positive integer it will be executed with the specified priority and arguments. If the step’s priority is zero, the step will not be executed.

If a core deploy step is included in a deploy template, it can only be assigned a priority of zero to disable it.

Creating a deploy template via API

A deploy template can be created using the Bare Metal API:

POST /v1/deploy_templates

Here is an example of the body of a request to create a deploy template with a single step:

{
    "name": "CUSTOM_HYPERTHREADING_ON",
    "steps": [
        {
            "interface": "bios",
            "step": "apply_configuration",
            "args": {
                "settings": [
                    {
                        "name": "LogicalProc",
                        "value": "Enabled"
                    }
                ]
            },
            "priority": 150
        }
    ]
}

Further information on this API is available here.

Creating a deploy template via “baremetal” client

A deploy template can be created via the baremetal deploy template create command, starting with python-ironicclient 2.7.0.

The argument --steps must be specified. Its value is one of:

  • a JSON string

  • path to a JSON file whose contents are passed to the API

  • ‘-‘, to read from stdin. This allows piping in the deploy steps.

Example of creating a deploy template with a single step using a JSON string:

baremetal deploy template create \
    CUSTOM_HYPERTHREADING_ON \
    --steps '[{"interface": "bios", "step": "apply_configuration", "args": {"settings": [{"name": "LogicalProc", "value": "Enabled"}]}, "priority": 150}]'

Or with a file:

baremetal deploy template create \
    CUSTOM_HYPERTHREADING_ON \
    ---steps my-deploy-steps.txt

Or with stdin:

cat my-deploy-steps.txt | baremetal deploy template create \
    CUSTOM_HYPERTHREADING_ON \
    --steps -

Example of use with the Compute service

Note

The deploy steps used in this example are for example purposes only.

In the following example, we first add the trait CUSTOM_HYPERTHREADING_ON to the node represented by $node_ident:

baremetal node add trait $node_ident CUSTOM_HYPERTHREADING_ON

We also update the flavor bm-hyperthreading-on in the Compute service with the following property:

openstack flavor set --property trait:CUSTOM_HYPERTHREADING_ON=required bm-hyperthreading-on

Creating a Compute instance with this flavor will ensure that the instance is scheduled only to Bare Metal nodes with the CUSTOM_HYPERTHREADING_ON trait.

We could then create a Bare Metal deploy template with the name CUSTOM_HYPERTHREADING_ON and a deploy step that enables Hyperthreading:

{
    "name": "CUSTOM_HYPERTHREADING_ON",
    "steps": [
        {
            "interface": "bios",
            "step": "apply_configuration",
            "args": {
                "settings": [
                    {
                        "name": "LogicalProc",
                        "value": "Enabled"
                    }
                ]
            },
            "priority": 150
        }
    ]
}

When an instance is created using the bm-hyperthreading-on flavor, then the deploy steps of deploy template CUSTOM_HYPERTHREADING_ON will be executed during the deployment of the scheduled node, causing Hyperthreading to be enabled in the node’s BIOS configuration.

To make this example more dynamic, let’s add a second trait CUSTOM_HYPERTHREADING_OFF to the node:

baremetal node add trait $node_ident CUSTOM_HYPERTHREADING_OFF

We could also update a second flavor, bm-hyperthreading-off, with the following property:

openstack flavor set --property trait:CUSTOM_HYPERTHREADING_OFF=required bm-hyperthreading-off

Finally, we create a deploy template with the name CUSTOM_HYPERTHREADING_OFF and a deploy step that disables Hyperthreading:

{
    "name": "CUSTOM_HYPERTHREADING_OFF",
    "steps": [
        {
            "interface": "bios",
            "step": "apply_configuration",
            "args": {
                "settings": [
                    {
                        "name": "LogicalProc",
                        "value": "Disabled"
                    }
                ]
            },
            "priority": 150
        }
    ]
}

Creating a Compute instance with the bm-hyperthreading-off instance will cause the scheduled node to have Hyperthreading disabled in the BIOS during deployment.

We now have a way to create Compute instances with different configurations, by choosing between different Compute flavors, supported by a single Bare Metal node that is dynamically configured during deployment.