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El Microkernel

This repository has the files/tools for building a Razor Microkernel based on RHEL/CentOS/Fedora. The resulting discovery image is used by the Razor server to take inventory of new machines.

Resources

Getting Started

This section describes how to build an image on a CentOS system.

Automated script

A script for building the microkernel on a vanilla build of CentOS exists in the bin/ directory, and is linked via short link. Run the script in a vanilla CentOS build with the following command:

curl -L pup.pt/build-razor-microkernel | sudo bash

Optionally, if the ruby version has changed from the version specified in the Gemfile, this can be specified as a parameter in the script:

curl -L pup.pt/build-razor-microkernel | sudo bash -s 2.7.0

Process explanation

First, install the necessary system dependencies. The system itself has been installed from the network infrastructure server role, with the compilers, rpmbuild tools, and system tools group selected.

yum -y install ruby livecd-tools
gem update --system && gem install rake bundler

Disable SELinux when building the image:

setenforce 0

Then, install project dependencies. Installing into a local path will require the use of bundle exec when starting project executables.

bundle install --path .bundle/gems/

To build an image, run the following on a CentOS machine:

bundle exec rake build
./build-livecd
sudo ./build-livecd-root

This will produce an ~ 130MB tar file microkernel.tar. To deploy this on an existing Razor server, extract it in the server's repo_store_root that you set in config.yaml:

> tar xf microkernel.tar -C $repo_store_root

For more information on the tools that do the heavy lifting of building the image, see the Fedora Live CD page

To log into the microkernel, use the root password thincrust. Also note that logging information will be sent to tty2.

Getting in touch

Razor Microkernel Client

The microkernel client has been broken out into several small, focused scripts intended to perform one task, well. They are designed to be fired off through cron, or through a process scheduling supervisor.

The entry point is the binary:

  • razor-submit-facts will discover and send facts about the node to Razor
    • this will also act on the command returned during that action

Razor Microkernel Client Configuration

Configuration is created by overlaying multiple sources, based on this priority map -- lower numbers are "more important" and override higher numbers. The intent is that more dynamic sources of data override less dynamic sources of data.

Sources are:

  1. Kernel command line (as read from /proc/cmdline)
  2. DHCP "next server" option (@todo danielp 2013-07-26: not implemented yet)
  3. Static, on-disk configuration file (/etc/razor-mk-client.json)
  4. A default DNS assumption that razor will point at your Razor server.

Any of these configuration options can be omitted with no ill effects.

In practice, the kernel command line is the place that almost all configuration will come from. This is set by the Razor server during boot, automatically, to help clients that boot from it to rendezvous correctly.

The static, on-disk configuration file is not expected to be used in most cases: this is provided as a convenience for users who, for some reason, want to boot statically from local media rather than through the Razor server, but still want to use the Razor MK image. (eg: through a virtual CD device, etc.)

Configuration options are:

  • ip the IP address of the Razor server.
  • server the DNS name of the Razor server.

If supplied, the ip value is preferred to the server value for locating the server. Both are supported since correctly functioning DNS is not assured during the early boot process; in general, you should strongly prefer to use the server value.

Razor Microkernel Client Identification

We supply a "hardware ID" value to the Razor server to help identify the specific hardware that is currently running: this is based on the MAC addresses of network adapters found in the current system.

Presently that is limited only to adapters with a visible name matching /^eth/, following the default naming convention for Linux wired Ethernet adapters.

@todo danielp 2013-07-26: we should fix that, because it is too limited, and will no longer work once F19 or F20 roll out their new "purpose and physical location" naming convention for network adapters.