# views/admins/index.html.erb
<%= link_to 'logout', :controller => 'sessions', :action => 'destroy' %>.

# controllers/sessions_controller.rb
class SessionsController < ApplicationController
  layout "sessions"

  def index
  end

  def create
    if params[:password] == 'foobar'
        session[:password] = true
        flash[:notice] = "Successfully logged in"
        redirect_to :controller => 'admins', :action => 'index'
    else
        flash[:notice] = "Invalid user/password combination"
        redirect_to :controller => 'sessions', :action => 'index'
    end
  end

  def destroy
    session[:password] = false
    flash[:notice] = "Successfully logged out"
    redirect_to :controller => 'sessions', :action => 'index'
  end
end

# the error when pressing the "logout" button on the index page
Unknown action

No action responded to show. Actions: create, destroy, and index