conmux/conmux.html

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   9 <title>conmux - the console multiplexor</title>
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  19 <h1>conmux - the console multiplexor</h1>
  20 </center>
  21
  22 <p><em>conmux</em>, the console multiplexor is a system designed to abstract
  23 the concept of a console.  That is to provide a virtualised machine interface,
  24 including access to the console and the 'switches' on the front panel; the
  25 /dev/console stream and the reset button.  It creates the concept of a virtual
  26 console server for multiple consoles and provides access to and sharing of
  27 consoles connected to it.
  28
  29 <p>There are two main motivations for wanting to do this.  Firstly, we have
  30 many different machine types with vastly differing access methodologies for
  31 their consoles and for control functions (VCS, HMC, Annex) and we neither want
  32 to know what they are nor how they function.  Secondly, most console sources
  33 are single access only and we would like to be able to share the console data
  34 between many consumers including users.
  35
  36 <h2>Basic Usage</h2>
  37
  38 <p>The main interface to the consoles is via the <code>console</code>
  39 program.  This connects us to the console server for the machine and allows us
  40 to interact with it, including issuing <i>out-of-band</i> commands to control
  41 the machine.
  42
  43 <div class="example">$ console &lt;host&gt;/&lt;console&gt;
  44 </div>
  45
  46 <p>In the example below  we indicate that the console we require is located on
  47 the virtual console server <code>consoles.here.com</code> and the
  48 specific console is <code>elm3b70</code>.
  49
  50 <div class="example">$ console consoles.here.com/elm3b70
  51 Connected to elm3b70 console (~$quit to exit)
  52
  53 Debian GNU/Linux 3.1 elm3b70 ttyS0
  54
  55 elm3b70 login:
  56 </div>
  57
  58 <p>Once connected we can interact normally with the console stream.  To
  59 perform front pannel operation such as peforming an <em>hard reset</em> we
  60 switch to command mode.  This is achieved using the escape sequence
  61 <code>~$</code>.  Nore the prompt <code>Command&gt;</code>
  62
  63 <div class="example">elm3b70 login: <em>~$</em>
  64 Command&gt; quit
  65 Connection closed
  66 $
  67 </div>
  68
  69 <h2>Command Summary</h2>
  70
  71 <p>The following commands are generally available:
  72
  73 <p><table class="quote" rules="all" frame="box">
  74
  75 <tr><th>Command<th>Description</tr>
  76
  77 <tr><td>quit<td>quit this console session, note that this disconnects us from
  78 the session it does not affect the integity of the session itself.</tr>
  79
  80 <tr><td>hardreset<td>force a hard reset on the machine, this may be a simple
  81 reset or a power off/on sequence whatever is required by this system.</tr>
  82
  83 </table>
  84
  85 <h2>Architecture</h2>
  86
  87 <p>The conmux provides a virtual console multiplexor system reminicent of
  88 an Annex terminal server.  You refer to the conmux <em>server</em> and
  89 <em>lines</em>, unlike an Annex lines are referred to by mnemonic names.
  90 Above we referred to the console for <code>elm3b70</code> 'connected to' the
  91 server <code>consoles.here.com</cond>.  A virtual console server consists
  92 of a number of server processes.  One <code>conmux-registry</code> server,
  93 several <code>conmux</code> servers and optionally several <em>helper</em>
  94 processes.
  95
  96 <p><code>conmux-registry</code>: a server is defined by the server registry.
  97 This maintains the mnemonic name to current server location relation.  When
  98 a client wishes to attach to a console on a server, the registry is first
  99 queried to locate the server currently handling that console.
 100
 101 <p><code>conmux</code>: for each connected console there is a corresponding
 102 console multiplexor.  This process is responsible for maintaining the
 103 connection to the console and for redistributing the output to the various
 104 connected clients.  It is also responsible for handling "panel" commands
 105 from the client channels.
 106
 107 <p><code>autoboot-helper</code>: an example helper which aids systems which
 108 are not capable of an automatic reboot.  It connects to a console and watches
 109 for tell-tale reboot activity, preforming a "panel" <em>hardreset</em> when
 110 required.  This provides the impression of seamless reboot for systems
 111 which this does not work.
 112
 113 <h2>Configuration</h2>
 114
 115 <h3>conmux-registry</h3>
 116
 117 <p>Configuration of this service is very simple.  Supplying the default
 118 registry port (normally 63000) and the location for the persistant registry
 119 database.
 120
 121 <h3>conmux</h3>
 122
 123 <p>Configuration of each conmux is complex.  Each has a listener, payload
 124 and optionally one or more panel commands.  Configuration is provided via
 125 a per console configuration file.  This file consists of lines defining each
 126 element:
 127
 128 <p><code>listener &lt;server&gt;/&lt;name&gt;</code>:
 129 defines the name of this console port as it appears in the registry.
 130
 131 <p><code>socket &lt;name&gt; &lt;title&gt; &lt;host&gt;:&lt;port&gt;</code>:
 132 defines a console payload connected to a tcp socket on the network.
 133 <code>name</code> defines this payload within the multiplexor,
 134 <code>title</code> is announced to the connecting clients.
 135
 136 <p><code>application &lt;name&gt; &lt;title&gt; &lt;cmd&gt;</code>:
 137 defines a console payload which is accessed by running a specific command.
 138 <code>name</code> defines this payload within the multiplexor,
 139 <code>title</code> is announced to the connecting clients.
 140
 141 <p><code>command &lt;panel&gt; &lt;message&gt; &lt;cmd&gt;</code>:
 142 defines a panel command for the preceeding payload, triggerd when
 143 <code>panel</code> is typed at the command prompt.  <code>message</code>
 144 is announced to the user community.  <code>cmd</cmd> will be actually
 145 executed.
 146
 147 <p>For example here is the configuration for a NUMA-Q system which is rebooted
 148 using a remote VCS console and for which the real console channel is
 149 on an Annex terminal server:
 150
 151 <div class="example">listener localhost/elm3b130
 152 socket console 'elm3b130 console' console.server.here.com:2040
 153   command 'hardreset' 'initated a hard reset' \
 154       './reboot-numaq vcs 1.2.3.4 elm3b130 12346 Administrator password'
 155 </div>
 156
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