Introduction to Ironic

“I can do any thing. I can’t do everything.”

The sheer number of projects and problem domains covered by OpenStack was overwhelming. I never learned several of the other projects under the big tent. One project that is getting relevant to my day job is Ironic, the bare metal provisioning service. Here are my notes from spelunking the code.

The Setting

I want just Ironic. I don’t want Keystone (personal grudge) or Glance or Neutron or Nova.

Ironic will write files to e.g. /var/lib/tftp and /var/www/html/pxe and will not handle DHCP, but can make sue of static DHCP configurations.

Ironic is just an API server at this point ( python based web service) that manages the above files, and that can also talk to the IPMI ports on my servers to wake them up and perform configurations on them.

I need to provide ISO images to Ironic so it can put the in the right place to boot them

Developer steps

I checked the code out of git. I am working off the master branch.

I ran tox to ensure the unit tests are all at 100%

I have mysql already installed and running, but with a Keystone Database. I need to make a new one for ironic. The database name, user, and password are all going to be ironic, to keep things simple.

CREATE USER 'ironic'@'localhost' IDENTIFIED BY 'ironic';
GRANT ALL PRIVILEGES ON ironic.* TO 'ironic'@'localhost';

Note that I did this as the Keystone user. That dude has way to much privilege….good thing this is JUST for DEVELOPMENT. This will be used to follow the steps in the developers quickstart docs. I also set the mysql URL in the config file to this

connection = mysql+pymysql://ironic:ironic@localhost/ironic

Then I can run ironic db sync. Lets’ see what I got:

mysql ironic --user ironic --password
MariaDB [ironic]> show tables;
| Tables_in_ironic              |
| alembic_version               |
| allocations                   |
| bios_settings                 |
| chassis                       |
| conductor_hardware_interfaces |
| conductors                    |
| deploy_template_steps         |
| deploy_templates              |
| node_tags                     |
| node_traits                   |
| nodes                         |
| portgroups                    |
| ports                         |
| volume_connectors             |
| volume_targets                |
15 rows in set (0.000 sec)

OK, so the first table shows that Ironic uses Alembic to manage migrations. Unlike the SQLAlchemy migrations table, you can’t just query this table to see how many migrations have been performed:

MariaDB [ironic]> select * from alembic_version;
| version_num  |
| cf1a80fdb352 |
1 row in set (0.000 sec)

Running The Services

The script to start the API server is:
ironic-api -d --config-file etc/ironic/ironic.conf.local

Looking in the file requirements.txt, I see that they Web framework for Ironic is Pecan:

$ grep pecan requirements.txt 
pecan!=1.0.2,!=1.0.3,!=1.0.4,!=1.2,>=1.0.0 # BSD

This is new to me. On Keystone, we converted from no framework to Flask. I’m guessing that if I look in the chain that starts with ironic-api file, I will see a Pecan launcher for a web application. We can find that file with

$which ironic-api

Looking in that file, it references ironic.cmd.api, which is the file ironic/cmd/ which in turn refers to ironic/common/ This in turn refers to ironic/api/ from which we can finally see that it imports pecan.

Now I am ready to run the two services. Like most of OpenStack, there is an API server and a “worker” server. In Ironic, this is called the Conductor. This maps fairly well to the Operator pattern in Kubernetes. In this pattern, the user makes changes to the API server via a web VERB on a URL, possibly with a body. These changes represent a desired state. The state change is then performed asynchronously. In OpenStack, the asynchronous communication is performed via a message queue, usually Rabbit MQ. The Ironic team has a simpler mechanism used for development; JSON RPC. This happens to be the same mechanism used in FreeIPA.

Command Line

OK, once I got the service running, I had to do a little fiddling around to get the command lines to work. The was an old reference to


which needed to be replaces with


Both are in the documentation, but only the second one will work.

I can run the following commands:

$ baremetal driver list
| Supported driver(s) | Active host(s) |
| fake-hardware       | ayoungP40      |
$ baremetal node list


Lets see if I can figure out from CURL what APIs those are…There is only one version, and one link, so:

curl | jq '.versions  | .[] | .links | .[] |  .href'

Doing curl against that second link gives a list of the top level resources:

  • media_types
  • chassis
  • nodes
  • drivers

And I assume that, if I use curl to GET the drivers, I should see the fake driver entry from above:

$ curl "" | jq '.drivers |.[] |.name'

OK, that is enough to get started. I am going to try and do the same with the RPMs that we ship with OSP and see what I get there.

But that is a tale for another day.

Thank You

I had a conversation I had with Julia Kreger, a long time core member of the Ironic project. This helped get me oriented.

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