December 12, 2011

Day 12 - Reverse-engineer servers with Blueprint


This was written by Richard Crowley (rcrowley.org)

The benefits of using a configuration management tool can be felt by even the smallest of teams, yet most still rely on wiki pages and handwritten shell scripts to keep things straight because the barriers to entry in traditional configuration management tools are too high, both mentally and technically.

You could be comfortable with how to configure a server by hand, but you don't know how to use the right tools to automate that configuration. We set out to build a configuration management tool that addresses common problems in an approachable way.

Blueprint is a simple configuration management tool that reverse-engineers servers. It figures out what you've done manually, stores it locally in a Git repository, generates code that's able to recreate your efforts, and helps you deploy those changes to production.

Once you get it installed, creating a blueprint takes but a single command:

blueprint create example

where 'example' is the name of your blueprint. Blueprint will list packages managed by APT, Yum, RubyGems, Python's easy_install and pip, PHP's PEAR and PECL, and Node.js' NPM. It will also determine which configuration files in /etc have been added or modified from their packaged versions and also collect files in /usr/local that are part of any software packages installed from source. Finally, it will build a list of conditions under which System V init or Upstart services should be restarted, including package upgrades and configuration changes.

Blueprints are stored in a local Git repository as JSON and tarballs and from there you can turn them into shell scripts, Puppet modules, or Chef cookbooks.

Generate a shell script rendering of this blueprint as example/bootstrap.sh:

blueprint show -S example

Generate a puppet module named 'example'; the main manifest will be example/manifests/init.pp:

blueprint show -P example

Generate a bit of chef with the recipe as example/recipes/default.rb:

blueprint show -C example

The generated shell scripts can render mustache.sh templates to tailor configuration to the hardware: {{CORES}} for the number of CPU cores in the system, {{MEM}} for total memory, {{FQDN}} for the fully-qualified domain name, and more. See blueprint-template(7) for the complete list and blueprint-template(1) to learn how to add your own template data.

There will undoubtedly come a time when you want to use a bit more finesse in configuration management than Blueprint's automatic reverse-engineering can provide, even with hints in /etc/blueprintignore. For that time, there are rules files that enumerate only the resources you want included in the blueprint. Take, for example, example.blueprint-rules describing a tiny Sinatra application:

:source:/usr/local

/etc/init/example.conf
/etc/nginx/sites-*/example
/etc/unicorn.conf.rb

:package:apt/libmysqlclient-dev
:package:apt/mysql-client-5.1
:package:apt/nginx-common
:package:apt/nginx-light
:package:apt/ruby-dev
:package:apt/rubygems
:package:rubygems/*

:service:sysvinit/nginx
:service:upstart/example

Regardless of what else is installed on the system, example will only contain these resources:

blueprint rules example.blueprint-rules

Blueprint still extracts file content and metadata, package versions, and service dependencies from the system but instead of including everything and the kitchen sink, stays focused only on the resources you declare.

There's much more detail in the newly-revamped documentation and copious man pages. Give Blueprint a spin and send questions to .

Further Reading

  • Blueprint can generate puppet modules and chef recipes and could be your gateway drug into learning more automation tools.
  • Vagrant could be used to help you automate testing of your blueprints.

1 comment :

samix said...

what about modules installed via cpan ?