DOS/V Power Report 2004 March/VPR0403.ISO/talks/147/paper.dkb

Extensible Markup Language | 2003-09-18 | 16.8 KB | 498 lines

<?xml version="1.0" encoding="ISO-8859-1"?>

<article id="paper-147">
  <articleinfo>
    <title>Automated Installation and System Configuration with AutoYaST</title>
    <author>
      <firstname>Anas</firstname>
      <surname>Nashif</surname>
    </author>
    <copyright>
      <year>2003</year>
      <holder>Anas Nashif</holder>
    </copyright>
  </articleinfo>


  <section>
    <title>Introduction</title>

    <para>
     AutoYaST is a system for installing one or more SuSE Linux systems
      automatically and without user intervention. AutoYaST installations
      are performed using  a control file with installation and configuration
      data. The control file can be created using the configuration insterface
      of AutoYaST and can be  provided to YaST2 during installation in
      different ways.

    </para>
    </section>



    <section>
      <title>Availability</title>
      <para>
    AutoYaST is available with recent  SuSE products starting
    from <emphasis>SuSE Linux 8.0</emphasis> and will be available with
    business products based on <emphasis>SLES 8</emphasis>.
      </para>
      <para>Old products prior to SuSE Linux 8.0 and business products based
    on <emphasis>SLES 7</emphasis> have an auto-installation
    system relying on <emphasis>YaST</emphasis>. A configuration management
    system is provided by <emphasis>Alice</emphasis> for these products.
      </para>

    </section>
    <section>
      <title>Motivation</title>
      <para>
    The <ulink url="http://www.linuxjournal.com/">Linux Journal</ulink>, in
    an article in <ulink
      url="http://www.linuxjournal.com/categories.php?op=newindex&catid=178">issue 78</ulink> writes:
      </para>
      <para>
    <quote>
      A standard Linux installation asks many questions about what to
      install, what hardware to configure, how to configure the network
      interface, etc. Answering these questions once is informative and maybe
      even fun. But imagine a system engineer who has to set up a new Linux
      network with a large number of machines. Now, the same issues need to
      be addressed and the same questions answered repeatedly. This makes the
      task very inefficient, not to mention a source of irritation and
      boredom. Hence, a need arises to automate this parameter and option
      selection.</quote>
      </para>
      <para>
    <quote>The thought of simply copying the hard disks naturally crosses one's
      mind. This can be done quickly, and all the necessary functions and
      software will be copied without option selection. However, the fact is
      that simple copying of hard disks causes the individual computers to
      become too similar. This, in turn, creates an altogether new mission of
      having to reconfigure the individual settings on each PC. For example,
      IP addresses for each machine will have to be reset. If this is not
      done properly, strange and inexplicable behavior results.</quote>
      </para>

      <para>
    Regular installation of SuSE Linux is semi-automated by default. The user is
    requested to select the necessary information at the beginning of the
    installation (Normally Language only) and YaST2  generates a
    proposal for the underlying system depending on different factors. In
    most cases, and especially for new systems, such a proposal needs not
    to be changed and can be used to install the system and provides a
    usable installation.
      </para>
      <para>
    The  steps following the proposal are  fully automated and the user is only
    prompted at the end of the installation to provide more information
    about the system.
      </para>
     <para>
    AutoYaST can be used where no user intervention is  required or
    where customization is required. Using  a control file, YaST2
    prepares the system for a custom installation and avoids any
    interaction with the user, unless specified in the file controling the installation.
      </para>
      <para>
    AutoYaST is not an automated GUI system. This means that in most
    cases many screen will be skipped, i.e. you will never see the language
    selection interface. AutoYaST will simply pass the language
    parameter to the sub-system without displaying any language related
    interface.
      </para>

       </section>

    <section>
      <title>Overview and Concept</title>
      <para>
    Using AutoYaST multiple systems sharing the same environment and
    similar but not necesserily  identical hardware performing similar
    tasks   can easily be installed in parallel and in a short time. A
    configuration  file (referred to as "control  file") is created using
    existing configuration resources. The control file can be easily
    tailored for any specific environment.
      </para>


      <para>
    Unlike autoinstallation systems available with older SuSE
    releases, AutoYaST is fully integrated and provides various options for
    installing and configuring a system. The main advantage over older
    systems and other auto-installation systems is the possibility to configure a
    computer  by using existing modules and avoiding using custom scripts which
    are normally executed at the end of the installation.
      </para>
    </section>

    <section>
      <title>Reasons why automated setup is needed?</title>

      <para>
    Several situations can make non-interactive installations necessary:
      </para>
      <itemizedlist>
    <listitem>
      <para>
        Installation of a large number of similar systems</para>
      <para>
        A large numer of client systems or servers for a special service, i.e. compute servers
        in a high performance cluster have to be installed in a similar manner. It
        would be too tedius to install every computer interactively. Automation is a
        necessary tool.
      </para>
    </listitem>
    <listitem>
      <para>
        Installation by less trained operators
      </para>
      <para>
        Server layout and selection of software and configuration of the main services
        is a challenging task normally done by well trained administrators and system
        architects. On the other hand, time of this well paid personal is very limited
        and often installations have to take place at distant locations. With the use
        of automation it is possible to \textit{design} and configure certain systems
        in advance and delegate the actual installation to operators in the local
        subsidary, for instance.

      </para>
    </listitem>

    <listitem>
      <para>
        Installation over a large distance
      </para>
      <para>

        Sometimes installation have to be made in locations without techical IT
        personal or over such large distances that travel expenses are too high. In
        these situations, it would be ideal if one could send a well prepared
        installation CD to the location and after booting the computer with this CD
        installed and a few minutes the computer is configured correctly and
        reachable through network services.

      </para>
    </listitem>
    <listitem>
      <para>
        Quality assurance for important server systems
      </para>
      <para>

        In a productive environment, one wishes to have a consistent set of
        servers who are identical in the layout and basic configuration. It is very
        hard to ensure this by written installation guides, etc. Using automation this
        is done by design and additionally one archives a good documentation of the
        installed systems.

      </para>
    </listitem>
      </itemizedlist>
    </section>




    <section>
      <title>Architecture</title>
      <para>
    The complete auto-installation process can be divided in three phases:
    Preparation, Installation and Configuration:
      </para>
      <para>
  <inlinemediaobject>
    <imageobject>
      <imagedata fileref="figure1-147.png" format="PNG"/>
    </imageobject>
  </inlinemediaobject>
    </para>
      <itemizedlist>
    <listitem>
      <para>
        Preparation: All relevant information about the target system is collected
        and turned into the appropriate directives of the control file. The control
        file is transferred onto the target system where its directives will be parsed
        and transformed to YaST2 conforming data.
      </para>
    </listitem>
    <listitem>
      <para>Installation: follows the instructions given in the control file and installs
        a base system.</para>
    </listitem>
    <listitem>
      <para>Configuration: YaST2 and some user-defined post-install scripts accomplish
        the system configuration</para>
    </listitem>
      </itemizedlist>
    </section>


    <section>

      <title>
    Features
      </title>
      <para>
    AutoYaST provides a lot of new features, starting from a graphical
    configuration management system to user defined postinstall options.
      </para>

      <section>
    <title>
      Configuration management system
    </title>
    <para>
      In order to create a control file or a certain class of control files, one can
      use a YaST module.
    </para>
      </section>

      <section>
    <title>
      Installation sources
    </title>
    <para>
      There are quite a number of different installation sources and control file
      sources.

      In the simplest scenario, one can use the standard SuSE Linux Enterprise Server CDs as installation
      sources and provide the control file on a DOS formatted floppy disk.

      In a more advanced situation, but without network connectivity, YaST can
      create a ISO image file wich contains all packages and the control file.

      Using the network, installation can be done using NFS (Network File System).
      Then the control file can be provided in different places:

    </para>


    <itemizedlist>
      <listitem><para>on a floppy disk</para></listitem>
      <listitem><para>in an NFS repository</para></listitem>
      <listitem><para>via HTTP, SMB or FTP</para></listitem>
      <listitem><para>TFTP</para></listitem>
    </itemizedlist>
    <para>
      Booting can be done via network (etherboot/PXE) or via CDROM.
    </para>

      </section>
      <section>
    <title>Hardware detection</title>
    <para>
      During autoinstall, the same convenient hardware detection is used as for
      interactive install using YaST. This is archieved through the complete
      integration of AutoYaST into the installation and configuration system.
    </para>
      </section>

      <section>
    <title>System Customization</title>
    <para>
      Most of the system customization is done in the second stage of the
      installation. YaST provides most of the important resources needed to bring
      up a system to a usable, general state. However, you may have other
      requirements for the installed system. If the required customizations can't be
      done using YaST resources, then the post-install scripts can be used to
      accomplish this task. You can define an unlimited number of custom scripts in
      the control file either by editing the control file or by using the
      configuration system.
    </para>
      </section>
    <section>
      <title>Rule Based Installation</title>

      <para>
    Rules offer the possibility to configure a system depending on system
    attributes by merging multiple control file during installation. The
    rules based installation is controlled by a rules file.
      </para>
      <para>
  <inlinemediaobject>
    <imageobject>
      <imagedata fileref="figure2-147.png" format="PNG"/>
    </imageobject>
  </inlinemediaobject>
    </para>
      <para>
    The rules file is an XML based file that contains
    rules for each group of systems (or single systems) that you want to
    automatically install. A set of rules distinguish a group of systems based on
    one or more system attributes, after passing all rules, it links each
    group of rules to a profile. Both the rules file and the profiles must be
    located in a pre-defined and accessible location.
      </para>
      <para>
    If more than one rule apply, the final profile for each group is generated
    on the fly using a merge script. The merging process is based on the
    order of the rules and later rules override configuration data in earlier rules.
      </para>
      <para>
    The use of  a rules file is optional. If the rules file is not found,
    system installation proceeds in the
    classic way by just using the supplied profile or by searching for the
    profile depending on the <emphasis>MAC</emphasis> or the
    <emphasis>IP</emphasis> address of the system.
      </para>
      <para>
    The following simple example illustrates how the rules file is used
    to retrieve the configuration for a client with known hardware.
      </para>
      <programlisting>
<![CDATA[
<?xml version="1.0"?>
<!DOCTYPE autoinstall SYSTEM "/usr/share/autoinstall/dtd/rules.dtd">
<autoinstall xmlns="http://www.suse.com/1.0/yast2ns" xmlns:config="http://www.suse.com/1.0/configns">
  <rules config:type="list">
    <rule>
       <disksize>
            <match>/dev/hdc 1000</match>
            <match_type>greater</match_type>
       </disksize>
       <result>
            <profile>machine1.xml</profile>
            <continue config:type="boolean">false</continue>
        </result>
    </rule>
    <rule>
       <disksize>
            <match>/dev/hda 1000</match>
            <match_type>greater</match_type>
       </disksize>
       <result>
            <profile>machine2.xml</profile>
            <continue config:type="boolean">false</continue>
        </result>
    </rule>
  </rules>
</autoinstall>
]]>
        </programlisting>



     <para>
    The last example defines 2 rules and provides a different profile for
    every rule. The rule used in this case is
    <emphasis>disksize</emphasis>. After parsing the rules file, YaST2
    attempts to match the system being installed to the rules in the
    <filename>rules.xml</filename> file in order: first rule through the
    last rule. A rule match occurs when the system being installed matches
    all of the system attributes defined in the rule. As soon as a system
    matches a rule, the result resource is added to the
    stack of profiles AutoYaST will be using to create the final
    profile.  The <emphasis>continue</emphasis> property tells AutoYaST if it should
    continue with other rules or not.
      </para>
      <para>
    If the first rule does not match,  next rule in the list is examined
    until a match is found.
      </para>
      <para>
    Using the <emphasis>disksize</emphasis> attribute, you can
    provide different configurations for different hard drives with
    different size. First rule checks if the device
    <emphasis>/dev/hdc</emphasis> is available and if it is greater than 1
    GB in size using the <emphasis>match</emphasis> property.
      </para>


      </section>

    </section>

  <section>
    <title>The Control File</title>
  <section id="Profile.Intro">
    <title>
      Introduction
    </title>

    <para>
      The control file is in most cases a  configuration description for a
      single system. It consists of
      sets of resources with properties including support for complex
      structures representations such as lists, records,  trees and large
      embedded or referenced objects.
    </para>


  </section>
  <section id="Profile.Format">
    <title>
      Format
    </title>

    <para>
      The XML configuration format provides a consistent file structure, which is
      easier to learn and remember when attempting to configure a new system.
    </para>
    <para>
      Using XML, you can eliminate (nearly) all of the configuration
      file parsing and error handling - an external  XML parser can do that instead
      - (especially if it is a validating parser). To make sure the control file is
      well-formatted and that the syntax is valid, you can run the control file
      through a validating parser before it is actually used for automatic
      installation. This is especially required if you prefer to edit the
      profile manually.
    </para>

    <para>
      The following example shows a control file in XML format:
    </para>

      <programlisting>
<![CDATA[
<?xml version="1.0"?>
<!DOCTYPE profile SYSTEM
 "/usr/share/autoinstall/dtd/profile.dtd">
 <profile
 xmlns="http://www.suse.com/1.0/yast2ns"
 xmlns:cfg="http://www.suse.com/1.0/configns">
 <install>
   <partitioning  config:type="list">
      <drive>
         <device>/dev/hda</device>
         <partition>
            <filesystem>ext2</filesystem>
            <size>520Mb</size>
            <mount>/</mount>
         </partition>
         <partition>
            <filesystem>reiser</filesystem>
            <size>1200Mb</size>
            <mount>/data</mount>
         </partition>
      </drive>
   </partitioning>
 </install>
 <configure>
   <scripts>
    <pre-scripts>
     <script>
        <interpreter>shell</interpreter>
    <filename>start.sh</filename>
         <source>
]]>
            <![CDATA[
        #!/bin/sh
        echo "Starting installation"
        exit 0
           ]]>
<![CDATA[
         </source>
     </script>
    </pre-scripts>
   </scripts>
 </configure>
</profile>
]]>

      </programlisting>

 </section>

  </section>
</article>