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Karl Matthias

DevOps, sysadmin, coder. Principal Systems Engineer at Nitro. Dublin, Ireland.

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Convert Chef Cookbooks to Puppet Modules

What if you, for any number of reasons, needed to convert Chef cookbooks to Puppet modules and it were convenient to do it in an automated way? How hard the task would be to convert the cookbook depends largely on how off the ranch the recipes are with respect to the Chef DSL.  Since Chef recipes are just Ruby code, you can write whatever you want into the recipe.  But if the recipes were written in a way that mostly sticks with the Chef DSL you can get fairly clean Puppet output in a really simple way: take advantage of the fact that Chef’s DSL is Ruby, and write a  system for evaluating the Chef DSL and generating Puppet syntax output.  I found this to be a surprisingly legitimate case for heavy meta-programming as much of the Chef DSL translates pretty well directly to Puppet.

Hopefully no one is ready to start a flame war at this point.  I am not suggesting that anyone use one system or the other.  I recently had the need to convert a lot of site-specific Chef code to Puppet so I wrote a tool to save me a lot of time.  The general approach is to convert as much of the Chef code to a module formatted for use in Puppet as possible.  You will need to edit the module when it is done being converted.  Chef makes an assumption about the relationship between resources based on order.  Puppet does no such thing.  So you will likely need to managed the dependencies yourself.  However, if you specified them explicitly in Chef, they will work in Puppet out of the box in most cases. There are currently only three options you need to specify to run the tool:

Usage: convert.rb [options]
-c, --cookbook COOKBOOK          Chef Cookbook directory (e.g. contains /recipes, /attributes...)
-o, --output-dir OUTPUT_DIR      Output directory (where modules are written)
-s, --server-name SERVER_NAME    The name of the Puppet server to be used in puppet:// URLs</pre>

Here is what the converter handles:

  • Converts cookbooks to a Puppet module directory structureg
  • Converts recipes to mostly-right Puppet manifests in the proper locationg
  • Copies templates to the correct location in the Puppet moduleg
  • Downloads remote_file resources into the Puppet module’s files directoryg
  • Tries to replace Chef’s node[:some][:var] variables with $some_var formatg
  • Edits templates to replace variable substitutions with the same formatg
  • Makes an attempt to replace not_if and only_if blocks with Puppet equivalentsg

I am still working with the tool and it will probably evolve over time.  But it has a pretty good success rate now.  Here’s some sample output:

$ ./convert.rb -c /tmp/chef-cookbooks/cookbooks/xen/ -o /tmp/asdf -s localhost.localdomain
Cookbook Name:   xen
Recipes Path:    /tmp/chef-cookbooks/cookbooks/xen/recipes
Templates Path:  /tmp/chef-cookbooks/cookbooks/xen/templates/default
Files Path:      /tmp/chef-cookbooks/cookbooks/xen/files/default
Output Path:     /tmp/asdf/xen
Working on recipe... /tmp/chef-cookbooks/cookbooks/xen/recipes/default.rb
Working on recipe... /tmp/chef-cookbooks/cookbooks/xen/recipes/dom0.rb
Fetching /xen/xen-Config.mk from some-bucket.s3.amazonaws.com to /tmp/asdf/xen/files/xen-Config.mk...
Fetching /xen/linux-2.6.31.12.tar.bz2 from some-bucket.s3.amazonaws.com to /tmp/asdf/xen/files/linux-2.6.31.12.tar.bz2...
Fetching /xen/patch-kernel.sh from some-bucket.s3.amazonaws.com to /tmp/asdf/xen/files/patch-kernel.sh...
Fetching /xen/xen-3.4-testing.tar.bz2 from some-bucket.s3.amazonaws.com to /tmp/asdf/xen/files/xen-3.4-testing.tar.bz2...
Fetching /xen/xen-patches-2.6.31-12.tar.bz2 from some-bucket.s3.amazonaws.com to /tmp/asdf/xen/files/xen-patches-2.6.31-12.tar.bz2...
Fetching /xen/make-initrd.sh from some-bucket.s3.amazonaws.com to /tmp/asdf/xen/files/make-initrd.sh...
Fetching /xen/initramfs_conf.tar.bz2 from some-bucket.s3.amazonaws.com to /tmp/asdf/xen/files/initramfs_conf.tar.bz2...
Fetching /xen/07_xen from some-bucket.s3.amazonaws.com to /tmp/asdf/xen/files/07_xen...
Modifying template /tmp/chef-cookbooks/cookbooks/xen/templates/default/xen-kernel-config.erb...

Code: (Find it on GitHub)[http://github.com/relistan/chef2puppet]


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