
  4. HOSTs-Sessions - Access to running OSs
  =========================================

   Host sessions are simple sessions to running instance of an
   OS. Therfore no seperate VM needs to be started. A HOSTs session is
   an ordinary login with some additional processes started as
   required.

   The available standard HOSTs sessions are CLI, X11, and VNC. 

   All of these are supported to be accessed via a SSH encryption
   only. Due to standardisation no specific parameters are supported,
   but a seperate ssh-call is performed. The callee is executed by the
   ssh encapsulation.


   4.1. Command Line Access - CLI
   ==============================

     This supports a command line interface, which is natively
     executed within the calling terminal, no new window is required,
     nor supported. Addional command execution is supported by
     specific suboptions.

     Thus this plugin supports for interactive sessions synchronous
     execution only, even though it is principally possible to use it
     asynchronously.

     The execution of remote commands by CLI could be performed more
     senceful, when the intermixin of output is not a drawback.

     The particular advantage is the usability from ASC-II terminals
     only, which do not support a graphical user interface.

     Therefore no graphic option is applicable for CLI, thus the type
     of forwarding is not relevant here.

     The onyl supported connection type is an encrypted ssh
     connection, thus the CLI module is more ore less an ssh
     connection with additional ctys-addressing capabilities.


   4.2. Start a GUI application - X11
   ==================================

     The X11 application supoports the stat of GUI applications. Therefore 
     any command could be provided and will be executed on the provided 
     execution target.

     Due to the stateful operations of X11 client and server
     architecture "DisplayForwarding" is the only supported operational
     mode.

     The asynchronous execution mode is the applied standard.

     The only supported connection type is an encrypted SSH channel
     with local access of X11 protocol only. Thus with the usage of
     ctys any X11 connection becomes a secure remote connection with
     encryption provided by ssh.


   4.3. Open a complete remote Desktop - VNC
   =========================================

     Another and meanwhile one of the most important remote execution
     facility is the VNC package. Which consists of a protocol
     definition and the implementing tools.

     This is important to recognise, due to the wide support of a so
     called VNCserver interface of VMs, where the attached console is
     the client component of one of the VNC packages only.

     Due to the splitted client and server components this plugin
     supports "DisplayForwarding" and "ConnectionForwarding". It could
     be used in this manner in combination with any supporting VM.

     Therefore encrypted connections are supported only. Due to the
     standards and design of internal libaries for automatic
     etsablishment of tunnels the OpenSSH package is supported
     only. Specific options of some packages are not used, even though
     they are just a wrapper for an SSH call.

