Tool to diff Puppet catalogs
Ruby Puppet
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NOTE: You should now use which is well maintained and recent :)

A tool to compare two Puppet catalogs.

While upgrading versions of Puppet or refactoring Puppet code you want to ensure that no unexpected changes will be made prior to doing the upgrade.

This tool will allow you to diff catalogs created by different versions of Puppet. This will let you guage the impact of a Puppet upgrade before actually touching any of your nodes.

This tool is delivered as a Puppet Face. It thus requires a Puppet installation to properly run.

The diff tool recognizes catalogs in yaml, marshall, or pson format.

Validation Process:

  • Grab a catalog from your existing machine running the old version

  • Configure your new Puppet master, copy the facts from your old master to the new one

  • Compile the catalog for this host on the new master:

    puppet master --compile fqdn > fqdn.pson

  • Puppet puts a header in some catalogs compiled in this way, remove it if present

  • At this point you should have two different catalogs. To compare them run:

    puppet catalog diff

Example Output:

During the transition of 0.24.x to 0.25.x there was a serialization bug that resulted in unexpected file content changes, I've recreated this bug in a tiny 2 resource catalog, the output below shows how this tool would have highlighted this bug prior to upgrading any nodes.

Resource counts:
  Old: 2
  New: 2

Catalogs contain the same resources by resource title

Individual Resource differences:
Old Resource:
    content => d3b07384d113edec49eaa6238ad5ff00

New Resource:
    content => dbb53f3699703c028483658773628452

Had resources simply gone missing - not the case here - you would have seen a list of that.

This code only validates the catalogs, it cannot tell you if the behavior of the providers that interpret the catalog has changed so testing is still recommended, this is just one tool to take away some of the uncertainty.

You can get some inline help with:

puppet man catalog


This version works best with Puppet 3.0.0 or newer, simply install it with the module tool into your module path:

# puppet module install ripienaar-catalog_diff
# puppet man catalog diff


  • 2012/10/20 - Make it a puppet face

  • 2010/10/19 - Change options and logic so it's easier to use comparing catalogs from the same version of puppet


R.I.Pienaar / / @ripienaar