Author: sbalneav
Date: Tue Aug 28 05:05:32 2007
New Revision: 4300
Modified:
trunk/edubuntu/handbook/C/server.xml
Log:
Little farther on the LDM documentation
Modified: trunk/edubuntu/handbook/C/server.xml
==============================================================================
--- trunk/edubuntu/handbook/C/server.xml (original)
+++ trunk/edubuntu/handbook/C/server.xml Tue Aug 28 05:05:32 2007
@@ -432,7 +432,7 @@
</para>
</listitem>
<listitem>
- <para>When
+ <para>When
<command>ipconfig</command> gets a reply from the
server, the
information it receives is used to configure the
ethernet
interface, and determine the server to mount the root
@@ -717,6 +717,80 @@
<para>We'll go over the <filename>lts.conf</filename> entries
you'll need to
control these features below.
</para>
+ <sect3>
+ <title>Theory of operation</title>
+ <para>To help understand the following sections, a bit of an
explanation
+ of how <command>ldm</command> does it's work is needed.
Most thin
+ client display managers tend to run up on the server. The
+ <command>ldm</command> display manager is unique in that
it runs on
+ the thin client itself. This allows the thin client to
have a lot
+ of choice as to how it will set up the connection. A
typical login
+ session goes as follows:
+ </para>
+ <itemizedlist>
+ <listitem>
+ <para><command>ldm</command>launches, and starts up
the X Windows
+ display on the thin client.
+ </para>
+ </listitem>
+ <listitem>
+ <para><command>ldm</command>starts up the greeter,
which is a
+ graphical program which presents the user with a
nice login
+ display, and allows them to select their session,
language,
+ and host they'd like to log into.
+ </para>
+ </listitem>
+ <listitem>
+ <para><command>ldm</command>collects the information
from the greeter,
+ and starts an ssh session with the server. This
ssh connection
+ is used to create an ssh master socket, which is
used by all
+ subsequent operations.
+ </para>
+ </listitem>
+ <listitem>
+ <para>Now, the users selected session is started via
the master
+ socket. Depending on whether or not an encrypted
connection
+ has been requested, vi the LDM_DIRECTX parameter,
the session
+ is either connected back to the local display via
the ssh tunnel,
+ or via a regular TCP/IP connection.
+ </para>
+ </listitem>
+ <listitem>
+ <para>During the session, any memory sticks, or other
local devices
+ that are plugged in, communicate their status to
the server via
+ the ssh control socket.
+ </para>
+ </listitem>
+ <listitem>
+ <para>When the user exits the session, the ssh
connection is closed
+ down, the X server is stopped, and
<command>ldm</command> restarts
+ itself, so everything starts with a clean slate.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </sect3>
+ <sect3>
+ <title>Encrypted versus unencrypted sessions</title>
+ <para>By default, LTSP5 encrypts the X session between the
server. This
+ makes your session more secure, but at the cost of
increased processing
+ power required on the thin client and on the server. If
processing
+ power is a concern to you, it's very easy to specify that
the connection
+ for either an individual workstation, or the default
setting should use
+ an unencrypted connection. To do so, simply specify:
+ </para>
+ <screen>
+LDM_DIRECTX=True
+ </screen>
+ <para>in your <filename>lts.conf</filename> file in the
appropriate stanza.
+ </para>
+ </sect3>
+ <sect3>
+ <title>Load balancing features</title>
+ <para>In this version of ltsp,
+ </para>
+ </sect3>
+
+
</sect2>
<sect2>
@@ -805,16 +879,16 @@
<command>Boolean values</command>
</term>
<listitem>
- <para>Throughout this guide, many
+ <para>Throughout this guide, many
<filename>lts.conf</filename> parameters
need a true or false value.
- For true values, any one of
- <command>Y</command>,
- <command>y</command>,
- <command>True</command>, or
- <command>true</command> will work. For
false values, any one of
- <command>N</command>,
- <command>n</command>,
- <command>False</command>, or
+ For true values, any one of
+ <command>Y</command>,
+ <command>y</command>,
+ <command>True</command>, or
+ <command>true</command> will work. For
false values, any one of
+ <command>N</command>,
+ <command>n</command>,
+ <command>False</command>, or
<command>false</command> will work.
</para>
</listitem>
@@ -850,7 +924,7 @@
<command>NBD_SWAP</command>
</term>
<listitem>
- <para>Set this to
+ <para>Set this to
<command>Y</command> if you want to turn
on NBD swap. The default is
<command>N</command>
</para>
@@ -885,7 +959,7 @@
<listitem>
<para>If you have a hard drive installed in
the thin client, with a
valid swap partition on it, this parameter
will allow the thin
- client to swap to the local hard drive.
The default is
+ client to swap to the local hard drive.
The default is
<command>N</command>.
</para>
</listitem>
@@ -898,7 +972,7 @@
<para>If the thin client is setup to have a
character based
interface, then the value of this
parameter will be used as the
host to telnet into. If this value is NOT
set, then it will use the
- value of
+ value of
<command>SERVER</command> above.
</para>
<para></para>
@@ -924,19 +998,19 @@
</varlistentry>
<varlistentry>
<term>
- <command>SCREEN_01</command> thru
+ <command>SCREEN_01</command> thru
<command>SCREEN_12</command>
</term>
<listitem>
<para>Up to 12 screen scripts can be specified
for a thin client.
This will give you up to 12 sessions on
the thin client, each
- accessible by pressing the Ctrl-Alt-F1
through Ctrl-Alt-F12 keys.
+ accessible by pressing the Ctrl-Alt-F1
through Ctrl-Alt-F12 keys.
<screen>
SCREEN_07 = ldm
SCREEN_02 = shell
</screen>
</para>
- <para>Currently, possible values include:
+ <para>Currently, possible values include:
<itemizedlist>
<listitem>
<para>
@@ -959,11 +1033,11 @@
<para>
<emphasis
role="bold">startx</emphasis>: This option can be used
for lower powered
installations that can't support the encryption
- that the
+ that the
<command>ssh</command> tunnel
provides. Enabling this will require
- you to turn on XDMCP for the
+ you to turn on XDMCP for the
<command>gdm</command> login
manager. As an administrative user, go
- to
+ to
<menuchoice>
<guimenu>System</guimenu>
<guisubmenu>Administration</guisubmenu>
@@ -973,7 +1047,7 @@
"Same as local". Additionally,
you may wish to click on the
"Configure XDMCP" button on
the lower corner, and increase the
"Maximum remote sessions" to
something a little higher than the
- number of thin clients you
have.
+ number of thin clients you
have.
<emphasis role="bold">Please
note that doing this means that all X
Windows traffic on your
network will be
unencrypted.
@@ -1008,22 +1082,22 @@
</varlistentry>
<varlistentry>
<term>
- <command>MODULE_01</command> thru
+ <command>MODULE_01</command> thru
<command>MODULE_10</command>
</term>
<listitem>
<para>Up to 10 kernel modules can be loaded by
using these
configuration entries. The entire command
line that you would use
- when running insmod can be specified here.
For example:
+ when running insmod can be specified here.
For example:
<screen>
MODULE_01 = uart401.o
MODULE_02 = "sb.o io=0x220 irq=5 dma=1"
MODULE_03 = opl3.o
</screen>
</para>
- <para>If the value of this parameter is an
absolute pathname, then
+ <para>If the value of this parameter is an
absolute pathname, then
<command>insmod</command> will be used to
load the module.
- Otherwise,
+ Otherwise,
<command>modprobe</command> will be used.
</para>
<para>In normal circumstances, you shouldn't
need to specify
@@ -1033,7 +1107,7 @@
</varlistentry>
<varlistentry>
<term>
- <command>RCFILE_01</command> thru
+ <command>RCFILE_01</command> thru
<command>RCFILE_10</command>
</term>
<listitem>
@@ -1760,7 +1834,7 @@
will sometimes find a bubble appear in the top right informing
you
that there are updates available for you computer.
</para>
-
+
<para>
<informalfigure>
<mediaobject>
@@ -1770,7 +1844,7 @@
</mediaobject>
</informalfigure>
</para>
-
+
<para> Any updates you
apply here will automatically be applied to all clients, though
they may require a reboot. This is because LTSP clients all
use the
@@ -1933,12 +2007,12 @@
Now that you have your Edubuntu server working, and are keeping it
updated,
you're going to want to back up your users' data.
</para>
-
+
<para>There are a variety of options available for external backup
media.
SCSI tape drives, DVD RAM or ROM's, or even CD/R's may all be used
to back
up your server on a regular basis.
</para>
-
+
<sect2 id="backupwhat" status="draft">
<title>What needs to be backed up?</title>
<para>When backing up a server, there are typically two
approaches:</para>
@@ -1951,7 +2025,7 @@
</listitem>
</itemizedlist>
<para>We'll look at each briefly.</para>
-
+
<sect3>
<title>Backup everything</title>
<para>Typically, by backing up everything, the administrator
is looking to
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