Looks like ohai had some name changes that broke Rserve.rb
https://github.com/chef/chef-web-docs/issues/259
See trivial fix below.

-Will

--- vagrant/chef-solo/cookbooks/R/recipes/Rserve.rb    (revision 42086)
+++ vagrant/chef-solo/cookbooks/R/recipes/Rserve.rb    (working copy)
@@ -18,7 +18,7 @@
 #
 ohai "reload_passwd" do
   action :nothing
- plugin "passwd"
+ plugin "etc"
 end