[chef] Running knife commands in the background(using rc.local)

[NagaLakshmi < >]

Hi,
I've written a rack application using grape which calls knife's bootstrap
command to bootstrap a VM.The following is the code to bootstrap
module Chef
 class Bootstrap < Grape::API
  format :json
  content_type :json,"application/json"
params do
        requires  :VM_IP, :type => String, :desc => "ip value"
        requires  :VM_username, :type => String, :desc => "username"
        requires  :VM_password, :type => String, :desc => "password"
end
resource :virtualmachine
     post 'bootstrap' do
        content_type "application/json" 
        status "200"
        body "Boostrapped Successfully!!!"
    
        t1 = Thread.new do
             system "knife chefsolo bootstrap #{params[:VM_IP]} -x
#{params[:VM_username]} -P '#{params[:VM_password]}'"
          end
        end
     end
    end
end

When i start the app manually using "rackup -p 9000 config.ru",the above code
is working fine,I've added this command to /etc/rc.local file to start the
service  during startup. The service has been started successfully but
bootstrapping is not working. I've tried replacing the knife commands with
other system commands and those are working fine.Only knife commands are not
working when i start the service in the background.Is there any specific 
reason
for it?How can i modify the code to make that working?