can't run bin/unicorn in vagrant when ebenv installed in /opt ?

[dfang]

i installed rbenv and ruby in a vagrant box(ubuntu 13.04), rbenv installed to /opt, i can't start unicorn in a rails 4 project with command: bin/unicorn, i also triefd sudo bin/unicorn, or bin/puma... however it works on mac. i don't know if it's a issue related to rbenv. i also tried rbenv-sudo plugin, it fails.

or maybe i need to install rbenv to a user's home diretory instead of /opt ?

here is the log: /vagrant/vendor/bundle/ruby/2.0.0/gems/kgio-2.9.2/lib/kgio.rb:21:inrequire': cannot load such file -- kgio_ext (LoadError) from /vagrant/vendor/bundle/ruby/2.0.0/gems/kgio-2.9.2/lib/kgio.rb:21:in <top (required)>' from /vagrant/vendor/bundle/ruby/2.0.0/gems/unicorn-4.8.2/lib/unicorn.rb:6:inrequire' from /vagrant/vendor/bundle/ruby/2.0.0/gems/unicorn-4.8.2/lib/unicorn.rb:6:in <top (required)>' from /vagrant/vendor/bundle/ruby/2.0.0/gems/unicorn-4.8.2/lib/unicorn/launcher.rb:9:inrequire' from /vagrant/vendor/bundle/ruby/2.0.0/gems/unicorn-4.8.2/lib/unicorn/launcher.rb:9:in <top (required)>' from /vagrant/vendor/bundle/ruby/2.0.0/gems/unicorn-4.8.2/bin/unicorn:3:inrequire' from /vagrant/vendor/bundle/ruby/2.0.0/gems/unicorn-4.8.2/bin/unicorn:3:in <top (required)>' from bin/unicorn:16:inload' from bin/unicorn:16:in <main>'

anyone can help ? thanks

[dfang]

tried to vagrant user to rbenv groups, doest not work