.htaccess

AuthType Kerberos
AuthName "ClueNet account shell"
KrbAuthRealms CLUENET.ORG
KrbServiceName HTTP
KrbMethodNegotiate on
KrbMethodK5Passwd on
Krb5Keytab /etc/apache2/http.sine.cluenet.org.keytab
KrbSaveCredentials On

# The rest is really in the VHost, but I'm putting it here for easy reading...
<Location /login>
  require valid-user
</Location>

new.html.erb

<pre>
<%= @klist %>
</pre>

sessions_controller.rb

class SessionsController < ApplicationController
  def new
    ENV['KRB5CCNAME'] = request.env['KRB5CCNAME']
    @klist =  `klist 2>&1`
  end

  def create
  end

end