install tacacs+ on ubuntu 12.04

command :
  sudo apt-get install tacacs+
edit  /etc/tacacs+/tac_plus.conf
  key = user_define
  user = testuser {
    login = cleartext "test1234"
    member = admins  
    service = exec {
      priv-lvl = 5
    }
  }
  user = $enable$ {

    login = cleartext "1234"
  }

  group = admins {
    default service = permit
#  login = PAM
  }