Installing Ironic Python Agent!

updated: 2019-05-21 23:39

Installing Ironic Python Agent!

Image Builders

Unlike most other python software, you must build an IPA ramdisk image before use. This is because it’s not installed in an operating system, but instead is run from within a ramdisk.

CoreOS

One way to build a ramdisk image for IPA is with the CoreOS image [0]. Prebuilt copies of the CoreOS image, suitable for pxe, are available on tarballs.openstack.org.

Build process

On a high level, the build steps are as follows:

  1. A docker build is performed using the Dockerfile in the root of the ironic-python-agent project.
  2. The resulting docker image is exported to a filesystem image.
  3. The filesystem image, along with a cloud-config.yml [1], are embedded into the CoreOS PXE image at /usr/share/oem/.
  4. On boot, the ironic-python-agent filesystem image is extracted and run inside a systemd-nspawn container. /usr/share/oem is mounted into this container as /mnt.

Customizing the image

There are several methods you can use to customize the IPA ramdisk:

  • Embed SSH keys by putting an authorized_keys file in /usr/share/oem/
  • Add your own hardware managers by modifying the Dockerfile to install additional python packages.
  • Modify the cloud-config.yml [1] to perform additional tasks at boot time.

diskimage-builder

Another way to build a ramdisk image for IPA is by using diskimage-builder [2]. The ironic-agent diskimage-builder element builds the IPA ramdisk, which installs all the required packages and configures services as needed.

tinyipa

Ironic Python Agent repo also provides a set of scripts to build a Tiny Core Linux-based deployment kernel and ramdisk (code name tinyipa) under imagebuild/tinyipa folder.

Tiny Core Linux is a very minimalistic Linux distribution. Due to its small size and decreased RAM requirements it is mostly suitable for usage in CI with virtualized hardware, and is already used on a number of gate jobs in projects under OpenStack Baremetal program. On the other hand, due to its generally newer Linux kernel it also known to work on real hardware if the kernel supports all necessary components installed.

Please refer to imagebuild/tinyipa/README.rst for more information and build instructions.

ISO Images

Additionally, the IPA ramdisk can be packaged inside of an ISO for use with supported virtual media drivers. Simply use the iso-image-create utility packaged with IPA, pass it an initrd and kernel. e.g.:

./iso-image-create -o /path/to/output.iso -i /path/to/ipa.initrd -k /path/to/ipa.kernel

This is a generic tool that can be used to combine any initrd and kernel into a suitable ISO for booting, and so should work against any IPA ramdisk created – both DIB and CoreOS.

IPA Flags

You can pass a variety of flags to IPA on start up to change its behavior. If you’re using the CoreOS image, you can modify the ironic-python-agent.service unit in cloud-config.yaml [3].

  • --standalone: This disables the initial lookup and heartbeats to Ironic. Lookup sends some information to Ironic in order to determine Ironic’s node UUID for the node. Heartbeat sends periodic pings to Ironic to tell Ironic the node is still running. These heartbeats also trigger parts of the deploy and cleaning cycles. This flag is useful for debugging IPA without an Ironic installation.
  • --debug: Enables debug logging.

IPA and SSL

During its operation IPA makes HTTP requests to a number of other services, currently including

  • ironic for lookup/heartbeats
  • ironic-inspector to publish results of introspection
  • HTTP image storage to fetch the user image to be written to the node’s disk (Object storage service or other service storing user images when ironic is running in a standalone mode)

When these services are configured to require SSL-encrypted connections, IPA can be configured to either properly use such secure connections or ignore verifying such SSL connections.

Configuration mostly happens in the IPA config file (default is /etc/ironic_python_agent/ironic_python_agent.conf) or command line arguments passed to ironic-python-agent, and it is possible to provide some options via kernel command line arguments instead.

Available options in the [DEFAULT] config file section are:

insecure
Whether to verify server SSL certificates. When not specified explicitly, defaults to the value of ipa-insecure kernel command line argument (converted to boolean). The default for this kernel command line argument is taken to be False. Overriding it to True by adding ipa-insecure=1 to the value of [pxe]pxe_append_params in ironic configuration file will allow running the same IPA-based deploy ramdisk in a CI-like environment when services are using secure HTTPS endpoints with self-signed certificates without adding a custom CA file to the deploy ramdisk (see below).
cafile
Path to the PEM encoded Certificate Authority file. When not specified, available system-wide list of CAs will be used to verify server certificates. Thus in order to use IPA with HTTPS endpoints of other services in a secure fashion (with insecure option being False, see above), operators should either ensure that certificates of those services are verifiable by root CAs present in the deploy ramdisk, or add a custom CA file to the ramdisk and set this IPA option to point to this file at ramdisk build time.
certfile
Path to PEM encoded client certificate cert file. This option must be used when services are configured to require client certificates on SSL-secured connections. This cert file must be added to the deploy ramdisk and path to it specified for IPA via this option at ramdisk build time. This option has an effect only when the keyfile option is also set.
keyfile
Path to PEM encoded client certificate key file. This option must be used when services are configured to require client certificates on SSL-secured connections. This key file must be added to the deploy ramdisk and path to it specified for IPA via this option at ramdisk build time. This option has an effect only when the certfile option is also set.

Currently a single set of cafile/certfile/keyfile options is used for all HTTP requests to the other services.

Securing IPA’s HTTP server itself with SSL is not yet supported in default ramdisk builds.

Hardware Managers

What is a HardwareManager?

Hardware managers are how IPA supports multiple different hardware platforms in the same agent. Any action performed on hardware can be overridden by deploying your own hardware manager.

Why build a custom HardwareManager?

Custom hardware managers allow you to include hardware-specific tools, files and cleaning steps in the Ironic Python Agent. For example, you could include a BIOS flashing utility and BIOS file in a custom ramdisk. Your custom hardware manager could expose a cleaning step that calls the flashing utility and flashes the packaged BIOS version (or even download it from a tested web server).

How can I build a custom HardwareManager?

Operators wishing to build their own hardware managers should reference the documentation available at Hardware Managers.

Indices and tables

updated: 2019-05-21 23:39
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