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 -- ubuntu-doc-commits mailing list ubuntu-doc-commits@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-doc-commits