Deploy Steps Tutorial

In this tutorial I'm showing how to create a custom deploy step for Ironic, how to build a ramdisk with in and how to use it when deploying a node.

Deploy steps are an answer to question "how do I run non-standard actions during deployment". Out-of-band steps run from your control plane and can talk to the BMC. More interesting for us are in-band steps that run from within the machine and offer nearly infinite opportunity for customization.

Today we'll create a solution for the following story:

As an operator, I would like to inject small files into the root partition of the final instance through the bare metal API.

There are, of course, numerous way of implementing it, cloud-init being probably the most popular. But we will concentrate on using a deploy step. The complete source code for this tutorial can be found here:

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Ephemeral Workloads with Ironic

In this post I'm presenting the ramdisk deploy interface, explaining how to use it to run ephemeral workloads and how to provide configuration data for them.

Ironic has been actively explored by the scientific community as a way to automate running calculations without incurring the costs of virtualization. This sort of workloads does not necessarily require installing anything on the machine's hard drive, which may instead be used for caching, swap or not used at all. The results are posted back via HTTP(s) or stored on a network share.

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