Have you ever had the nuisance of configuring a server BIOS? How about a rack full of servers? Or an aisle, a hall, an entire facility even? It gets to be tedious toil even before the second server, and it also becomes increasingly unreliable to apply a consistent configuration with increasing scale.
In this post we describe how we apply some modern tools from the cloud toolbox (Ansible, Ironic and Python) to tackle this age-old problem.
Server Management in the 21st Century
Baseboard management controllers (BMCs) are a valuable tool for easing the inconvenience of hardware management. By using a BMC we can configure our firmware using remote access, avoiding a trip to the data centre and stepping from server to server with a crash cart. This is already a big win.
However, BMCs are still pretty slow to apply changes, and are manipulated individually. Through automation, we could address these shortcomings.
I've seen some pretty hairy early efforts at automation, for example playing out timed keystroke macros across a hundred terminals of BMC sessions. This might work, but it's a desperate hack. Using the tools created for configuration management we can do so much better.
A Quick Tour of OpenStack Server Hardware Management
OpenStack deployment usually draws upon some hardware inventory management intelligence. In our recent project with the University of Cambridge this was Red Hat OSP Director. The heart of OSP Director is TripleO and the heart of TripleO is OpenStack Ironic.
Ironic is OpenStack's bare metal manager. It masquerades as a virtualisation driver for OpenStack Nova, and provisions bare metal hardware when a user asks for a compute instance to be created. TripleO uses this capability to good effect to create OpenStack-on-OpenStack (OoO), in which the servers of the OpenStack control plane are instances created within another OpenStack layer beneath.
iDRAC: Dell's Server Management Toolkit
The system at Cambridge makes extensive use of Dell server hardware, including:
- R630 servers for OpenStack controllers.
- C6320 servers for high-density compute nodes.
- R730 servers for high performance storage.
Deploying a diverse range of servers in a diverse range of roles requires flexible (but consistent) management of firmware configuration.
These Dell server models feature Dell's proprietary BMC, the integrated Dell Remote Access Controller (iDRAC). This is what we use for remote configuration of our Dell server hardware.
A Cloud-centric Approach to Firmware Configuration Management
OpenStack Ironic tracks hardware state for every server in an OpenStack deployment.
A simple overview can be seen with ironic node-list:
+--------------------------------------+----------+--------------------------------------+-------------+--------------------+-------------+ | UUID | Name | Instance UUID | Power State | Provisioning State | Maintenance | +--------------------------------------+----------+--------------------------------------+-------------+--------------------+-------------+ | 415c254f-3e82-446d-a63b-232af5816e4e | control1 | 3d27b7d2-729c-467c-a21b-74649f1b1203 | power on | active | False | | 2646ece4-a24e-4547-bbe8-786eca16da82 | control2 | 8a066c7e-36ec-4c45-9e1b-5d0c5635f256 | power on | active | False | | 2412f0ef-dedb-49c8-a923-778db36a57d9 | control3 | 6a62936f-40ec-49e7-a820-6f3329e5bb0c | power on | active | False | | 81676b2d-9c37-4111-a32a-456a9f933e57 | compute0 | aac2866c-7d16-4089-9d94-611bfc38467e | power on | active | False | | c6a5fbe7-566a-447e-a806-9e33676be5ea | compute1 | 619476ae-fec4-42c6-b3f5-3a4f5296d3bc | power on | active | False | | c7f27dd4-67a7-42b9-93ab-2e444802c5c2 | compute2 | a074c3f8-eb87-46d6-89c8-f360fbf2a3df | power on | active | False | | 025d84dc-a590-46c5-a456-211d5c1e8f1a | compute3 | 11524318-2ecf-4880-a1cf-76cd62935b00 | power on | active | False | +--------------------------------------+----------+--------------------------------------+-------------+--------------------+-------------+
Ironic's node data includes how to access the BMC of every server in the node inventory.
We extract the data from Ironic's inventory to generate a dynamic inventory for use with Ansible. Instead of a file of hostnames, or a list of command line parameters, a dynamic inventory is the output from an executed command. A dynamic inventory executable accepts a few simple arguments and emits node inventory data in JSON format. Using Python and the ironicclient module simplifies the implementation.
To perform fact gathering and configuration, two new Ansible roles were developed and published on Ansible Galaxy.
- DRAC configuration
- Provides the drac Ansible module for configuration of BIOS settings and RAID controllers. A single task is provided to execute the module. The role is available on Ansible Galaxy as stackhpc.drac and the source code is available on Github as stackhpc/drac.
- DRAC fact gathering
- Provides the drac_facts Ansible module for gathering facts from a DRAC card. The module is not executed by this role but is available to subsequent tasks and roles. The role is available on Ansible Galaxy as stackhpc.drac-facts and the source code is available on Github as stackhpc/drac-facts.
We use the python-dracclient module as a high-level interface for querying and configuring the DRAC via the WSMAN protocol. This module was developed by the Ironic team to support the DRAC family of controllers. The module provides a useful level of abstraction for these Ansible modules, hiding the complexities of the WSMAN protocol.
The source code for all of the following examples is available on Github at stackhpc/ansible-drac-examples. The playbooks are not large, and we encourage you to read through them.
A Docker image providing all dependencies has also been created and made available on Dockerhub at the stackhpc/ansible-drac-examples repository. To use this image, run:
$ docker run --name ansible-drac-examples -it --rm docker.io/stackhpc/ansible-drac-examples
This will start a Bash shell in the /ansible-drac-examples directory where there is a checkout of the ansible-drac-examples repository. The stackhpc.drac and stackhpc.drac-facts roles are installed under /etc/ansible/roles/. Once the shell is exited the container will be removed.
In the example repository, the inventory script is inventory/ironic_inventory.py. We need to provide this script with the following environment variables to allow it to communicate with Ironic: OS_USERNAME, OS_PASSWORD, OS_TENANT_NAME and OS_AUTH_URL. For the remainder of this article we will assume that a file, cloudrc, is available and exports these variables. To see the output of the inventory script:
$ source cloudrc $ ./inventory/ironic_inventory.py --list
To use this dynamic inventory with ansible-playbook, use the -i argument:
$ source cloudrc $ ansible-playbook -i inventory ...
The inventory will contain all Ironic nodes, named by their UUID. For convenience, an Ansible group is created for each named node using its name with a prefix of node_.
The inventory also contains groupings for servers in Ironic maintenance mode, and for servers in different states in Ironic's hardware state machine. Groups are also created for each server profile defined by TripleO: controller, compute, block-storage, etc..
In the following examples, the playbooks will execute against all Ironic nodes discovered by the inventory script. To limit the hosts against which a play is executed, use the --limit argument to ansible-playbook.
If you would rather not make any changes to the systems in the inventory, use the --check argument to ansible-playbook. This will display the changes that would have been made if the --check argument were not passed.
Example 1: Gather and Display Facts About Firmware Configuration
The drac-facts.yml playbook shows how the stackhpc.drac-facts role can be used to query the DRAC module of each node in the inventory. It also displays the results. Run the following command to execute the playbook:
$ source cloudrc $ ansible-playbook -i inventory drac-facts.yml
Example 2: Configure the NumLock BIOS Setting
NOTE: This example may make changes to systems in the inventory.
The drac-bios-numlock.yml playbook demonstrates how the stackhpc.drac role can be used to configure BIOS settings. It sets the NumLock BIOS setting to either On or Off.
The playbook specifies the drac_reboot variable as False, so the setting will not be applied immediately. A reboot of the system is required for this pending setting to be applied. The drac_facts module provides information on any pending BIOS configuration changes, as may be seen in the first example.
Run the following command to execute the playbook and configure the setting:
$ source cloudrc $ ansible-playbook -i inventory -e numlock=<value> drac-bios-numlock.yml
Set the numlock variable to the required value (On or Off). The drac_result variable is registered by the role and contains the results returned by the drac module. The playbook displays this variable after the role is executed. Of particular interest is the reboot_required variable which indicates whether a reboot is required to apply the changes. If a reboot is required, this must be performed before making further BIOS configuration changes.
Example 3: Configure a RAID-1 Virtual Disk
NOTE: This example may make changes to systems in the inventory.
The drac-raid1.yml playbook shows how the stackhpc.drac role can be used to configure RAID controllers. In this example we configure a RAID1 virtual disk.
Ensure that raid_pdisk1 and raid_pdisk2 are set to the IDs of two physical disks in the system that are attached to the same RAID controller and not already part of another virtual disk. The facts gathered in the first example may be useful here. This time we specify the drac_reboot variable as True. This means that if required, the drac module will reboot the system to apply changes.
Run the following command to execute the playbook and configure the system. The task will likely take a long time to execute if the virtual disk configuration is not already as requested, as the system will need to be rebooted:
$ source cloudrc $ ansible-playbook -i inventory -e raid_pdisk1=<pdisk1> -e raid_pdisk2=<pdisk2> drac-raid1.yml
Under The Hood
The vast majority of the useful code provided by these roles takes the form of python Ansible modules. This takes advantage of the capability of Ansible roles to contain modules under a library directory, and means that no python code needs to be installed on the system or included with the core or extra Ansible modules.
The drac_facts Module
The drac_facts module is relatively simple. It queries the state of BIOS settings, RAID controllers and the DRAC job queues. The results are translated to a JSON-friendly format and returns them as facts.
The drac Module
The drac module is more complex than the drac_facts module. The DRAC API provides a split-phase execution model, allowing changes to be staged before either committing or aborting them. Committed changes are applied by rebooting the system. To further complicate matters, the BIOS settings and each of the RAID controllers represents a separate configuration channel. Upon execution of the drac module these channels may have uncommitted or committed pending changes. We must therefore determine a minimal sequence of steps to realise the requested configuration for an arbitrary initial state, which may affect more than one of these channels.
The python-dracclient module provided almost all of the necessary input data with one exception. When querying the virtual disks, the returned objects did not contain the list of physical disks that each virtual disk is composed of. We developed the required functionality and submitted it to the python-dracclient project.
Thanks go to the python-dracclient community for their help in implementing the feature.