I did what someone else perhaps has done as a good workaround -- modify the facter fact for operatingsystemrelease since foreman is expecting major.minor

I added this to operatingsystemrelease.rb before the "catch-all" entry at the end.

Facter.add(:operatingsystemrelease) do
  confine :operatingsystem => :aix
  setcode 'oslevel | cut -c1-3'
end

Then AIX gets added to the database and it shows up correctly on the hosts and statistics pages.

Actually, I also had to create app/models/aix.rb. It would not work for provisioning, but it does the job otherwise:

class AIX < Operatingsystem

  PXEFILES = {:kernel => "powerpc", :initrd => "initrd"}

  # Override the class representation, as this breaks many rails helpers
  def class
    Operatingsystem
  end

  def pxe_type
    "nim" 
  end

  def pxedir
    "boot/$arch/loader" 
  end

  def url_for_boot(file)
    pxedir + "/" + PXEFILES[file]
  end

end

great job!
not 100% sure why would you need to add the Aix OS type, did you get any other errors without it?

and while we are at it, any chance you want to add an AIX icon? :)

Unfortunately, I'm not aware of any copyright free images for AIX. Otherwise, this is a nice one -- http://en.wikipedia.org/wiki/File:IBM-AIX_logo20080906.png :)

Yes, I did get an error without it:

The single-table inheritance mechanism failed to locate the subclass: 'AIX'. This error is raised because the column 'type' is reserved for storing the class in case of inheritance. Please rename this column if you didn't intend it to be used for storing the inheritance class or overwrite Operatingsystem.inheritance_column to use another column for that information.

Because we are using AIX i also added this to operatingsystems_helper.rb (/usr/share/foreman/app/helpers)

  when /gentoo/i
      "Gentoo" 
  when /SLC/i
      "SLC" 
  when /AIX/i
      "AIX" 
    else

And in manifest.yaml (/usr/share/foreman/public/assets)

---
AIX.png: AIX.png

Hi,

By using Ruediger Mueck's modifications and patching /usr/share/foreman/app/services/facts_importer.rb in Foreman, AIX hosts finally show up on the hosts page. I did not want to directly patch the operatingsystemrelease fact because it would be too complicated to manage the facter package upgrade.

Here is the patch :

--- facts_importer.rb.old    2013-10-30 09:40:50.000000000 +0100
+++ facts_importer.rb    2013-10-30 09:34:50.000000000 +0100
@@ -28,6 +28,9 @@
             when /sid/i
               orel = "99" 
           end
+        elsif os_name[/AIX/i]
+            majoraix, tlaix, spaix, yearaix = orel.split("-")
+            orel = majoraix + "." + tlaix + spaix
         end
         major, minor = orel.split(".")
         major.to_s.gsub!(/\D/,'') unless is_numeric? major