[myplc.git] / doc / myplc.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
"http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [
  <!ENTITY Variables SYSTEM "plc_variables.xml">
  <!ENTITY DevelVariables SYSTEM "plc_devel_variables.xml">
]>
<article>
  <articleinfo>
    <title>MyPLC User's Guide</title>

    <author>
      <firstname>Mark Huang</firstname>
    </author>

    <affiliation>
      <orgname>Princeton University</orgname>
    </affiliation>

    <abstract>
      <para>This document describes the design, installation, and
      administration of MyPLC, a complete PlanetLab Central (PLC)
      portable installation contained within a
      <command>chroot</command> jail. This document assumes advanced
      knowledge of the PlanetLab architecture and Linux system
      administration.</para>
    </abstract>

    <revhistory>
      <revision>
        <revnumber>1.0</revnumber>
        <date>April 7, 2006</date>
        <authorinitials>MLH</authorinitials>
        <revdescription><para>Initial draft.</para></revdescription>
      </revision>
      <revision>
        <revnumber>1.1</revnumber>
        <date>July 19, 2006</date>
        <authorinitials>MLH</authorinitials>
        <revdescription><para>Add development environment.</para></revdescription>
      </revision>
    </revhistory>
  </articleinfo>

  <section>
    <title>Overview</title>

    <para>MyPLC is a complete PlanetLab Central (PLC) portable
    installation contained within a <command>chroot</command>
    jail. The default installation consists of a web server, an
    XML-RPC API server, a boot server, and a database server: the core
    components of PLC. The installation is customized through an
    easy-to-use graphical interface. All PLC services are started up
    and shut down through a single script installed on the host
    system. The usually complex process of installing and
    administering the PlanetLab backend is reduced by containing PLC
    services within a virtual filesystem. By packaging it in such a
    manner, MyPLC may also be run on any modern Linux distribution,
    and could conceivably even run in a PlanetLab slice.</para>

    <figure id="Architecture">
      <title>MyPLC architecture</title>
      <mediaobject>
        <imageobject>
          <imagedata fileref="architecture.eps" format="EPS" align="center" scale="50" />
        </imageobject>
        <imageobject>
          <imagedata fileref="architecture.png" format="PNG" align="center" scale="50" />
        </imageobject>
        <textobject>
          <phrase>MyPLC architecture</phrase>
        </textobject>
        <caption>
          <para>MyPLC should be viewed as a single application that
          provides multiple functions and can run on any host
          system.</para>
        </caption>
      </mediaobject>
    </figure>

    <section> <title> Purpose of the <emphasis> myplc-devel
    </emphasis> package </title>
    <para> The <emphasis>myplc</emphasis> package comes with all
    required node software, rebuilt from the public PlanetLab CVS
    repository. If for any reason you need to implement your own
    customized version of this software, you can use the
    <emphasis>myplc-devel</emphasis> package instead, for setting up
    your own development environment, including a local CVS
    repository; you can then freely manage your changes and rebuild
    your customized version of <emphasis>myplc</emphasis>. We also
    provide good practices, that will then allow you to resync your local
    CVS repository with any further evolution on the mainstream public
    PlanetLab software. </para> </section>

    </section>


  <section id="Requirements"> <title> Requirements </title>

  <para> <emphasis>myplc</emphasis> and
  <emphasis>myplc-devel</emphasis> were designed as
  <command>chroot</command> jails so as to reduce the requirements on
  your host operating system. So in theory, these distributions should
  work on virtually any Linux 2.6 based distribution, whether it
  supports rpm or not. </para>

  <para> However, things are never that simple and there indeed are
  some known limitations to this, so here are a couple notes as a
  recommended reading before you proceed with the installation.</para>

  <para> As of 17 August 2006 (i.e <emphasis>myplc-0.5-2</emphasis>) :</para>

  <itemizedlist>
  <listitem><para> The software is vastly based on <emphasis>Fedora
  Core 4</emphasis>. Please note that the build server at Princeton
  runs <emphasis>Fedora Core 2</emphasis>, togother with a upgraded
  version of yum. 
  </para></listitem>

  <listitem><para> myplc and myplc-devel are known to work on both
  <emphasis>Fedora Core 2</emphasis> and <emphasis>Fedora Core
  4</emphasis>. Please note however that, on fc4 at least, it is
  highly recommended to use the <application>Security Level
  Configuration</application> utility and to <emphasis>switch off
  SElinux</emphasis> on your box because : </para>

  <itemizedlist>
  <listitem><para>
  myplc requires you to run SElinux as 'Permissive' at most
        </para></listitem>
  <listitem><para>
  myplc-devel requires you to turn SElinux Off.
        </para></listitem>
  </itemizedlist>
  </listitem>

  <listitem> <para> In addition, as far as myplc is concerned, you
  need to check your firewall configuration since you need, of course,
  to open up the <emphasis>http</emphasis> and
  <emphasis>https</emphasis> ports, so as to accept connections from
  the managed nodes and from the users desktops. </para> </listitem>

  </itemizedlist>
  </section>

  <section id="Installation">
    <title>Installating and using MyPLC</title>

    <para>Though internally composed of commodity software
    subpackages, MyPLC should be treated as a monolithic software
    application. MyPLC is distributed as single RPM package that has
    no external dependencies, allowing it to be installed on
    practically any Linux 2.6 based distribution.</para>

    <section>
      <title>Installing MyPLC.</title>

      <itemizedlist>
      <listitem> <para>If your distribution supports RPM:</para>
      <programlisting><![CDATA[# rpm -U http://build.planet-lab.org/build/myplc-0_4-rc1/RPMS/i386/myplc-0.4-1.planetlab.i386.rpm]]></programlisting></listitem>

      <listitem> <para>If your distribution does not support RPM:</para>
<programlisting><![CDATA[# cd /tmp
# wget http://build.planet-lab.org/build/myplc-0_4-rc1/RPMS/i386/myplc-0.4-1.planetlab.i386.rpm
# cd /
# rpm2cpio /tmp/myplc-0.4-1.planetlab.i386.rpm | cpio -diu]]></programlisting></listitem>
    </itemizedlist>

    <para> The <xref linkend="FilesInvolvedRuntime" /> below explains in
    details the installation strategy and the miscellaneous files and
    directories involved.</para>
 
    </section>

    <section id="QuickStart"> <title> QuickStart </title>

    <para> On a Red Hat or Fedora host system, it is customary to use
    the <command>service</command> command to invoke System V init
    scripts. As the examples suggest, the service must be started as root:</para> 

    <example><title>Starting MyPLC:</title>
          <programlisting><![CDATA[# service plc start]]></programlisting>
    </example>
    <example><title>Stopping MyPLC:</title>
          <programlisting><![CDATA[# service plc stop]]></programlisting>
    </example>

    <para> In <xref linkend="StartupSequence" />, we provide greater
    details that might be helpful in the case where the service does
    not seem to take off correctly.</para>

    <para>Like all other registered System V init services, MyPLC is
    started and shut down automatically when your host system boots
    and powers off. You may disable automatic startup by invoking the
    <command>chkconfig</command> command on a Red Hat or Fedora host
    system:</para>

    <example> <title>Disabling automatic startup of MyPLC.</title>
    <programlisting><![CDATA[# chkconfig plc off]]></programlisting></example>
    <example> <title>Re-enabling automatic startup of MyPLC.</title>
    <programlisting><![CDATA[# chkconfig plc on]]></programlisting></example>

    </section>

    <section id="Configuration">
      <title>Changing the configuration</title>

      <para>After verifying that MyPLC is working correctly, shut it
      down and begin changing some of the default variable
      values. Shut down MyPLC with <command>service plc stop</command>
      (see <xref linkend="QuickStart" />). </para>

      <para> The preferred option for changing the configuration is to
      use the <command>plc-config-tty</command> tool. This tools comes
      with the root image, so you need to have it mounted first. The
      full set of applicable variables is described in <xref
      linkend="VariablesDevel" />, but using the <command>u</command>
      guides you to the most useful ones. Here is sample session:
      </para>

      <example><title>Using plc-config-tty for configuration:</title>
          <programlisting><![CDATA[# service plc mount
Mounting PLC:                                              [  OK  ]
# chroot /plc/root su - 
<plc> # plc-config-tty
Config file /etc/planetlab/configs/site.xml located under a non-existing directory
Want to create /etc/planetlab/configs [y]/n ? y
Created directory /etc/planetlab/configs
Enter command (u for usual changes, w to save, ? for help) u
== PLC_NAME : [PlanetLab Test] OneLab
== PLC_ROOT_USER : [root@localhost.localdomain] odie.inria.fr
== PLC_ROOT_PASSWORD : [root] plain-passwd
== PLC_MAIL_SUPPORT_ADDRESS : [root+support@localhost.localdomain] support@one-lab.org
== PLC_DB_HOST : [localhost.localdomain] odie.inria.fr
== PLC_API_HOST : [localhost.localdomain] odie.inria.fr
== PLC_WWW_HOST : [localhost.localdomain] odie.inria.fr
== PLC_BOOT_HOST : [localhost.localdomain] odie.inria.fr
== PLC_NET_DNS1 : [127.0.0.1] 138.96.250.248
== PLC_NET_DNS2 : [None] 138.96.250.249
Enter command (u for usual changes, w to save, ? for help) w
Wrote /etc/planetlab/configs/site.xml
Merged
        /etc/planetlab/default_config.xml
and     /etc/planetlab/configs/site.xml
into    /etc/planetlab/plc_config.xml
You might want to type 'r' (restart plc) or 'q' (quit)
Enter command (u for usual changes, w to save, ? for help) r
==================== Stopping plc
...
==================== Starting plc
...
Enter command (u for usual changes, w to save, ? for help) q
<plc> # exit
# 
]]></programlisting>
    </example>

      <para>If you used this method for configuring, you can skip to
      the next section. As an alternative to using
      <command>plc-config-tty</command>, you may also use a text
      editor, but this requires some understanding on how the
      configuration files are used within myplc. The
      <emphasis>default</emphasis> configuration is stored in a file
      named <filename>/etc/planetlab/default_config.xml</filename>,
      that is designed to remain intact. You may store your local
      changes in any file located in the <filename>configs/</filename>
      sub-directory, that are loaded on top of the defaults. Finally
      the file <filename>/etc/planetlab/plc_config.xml</filename> is
      loaded, and the resulting configuration is stored in the latter
      file, that is used as a reference.</para>

      <para> Using a separate file for storing local changes only, as
      <command>plc-config-tty</command> does, is not a workable option
      with a text editor because it would involve tedious xml
      re-assembling. So your local changes should go in
      <filename>/etc/planetlab/plc_config.xml</filename>. Be warned
      however that any change you might do this way could be lost if
      you use <command>plc-config-tty</command> later on. </para>

      <para>This file is a self-documenting configuration file written
      in XML. Variables are divided into categories. Variable
      identifiers must be alphanumeric, plus underscore. A variable is
      referred to canonically as the uppercase concatenation of its
      category identifier, an underscore, and its variable
      identifier. Thus, a variable with an <literal>id</literal> of
      <literal>slice_prefix</literal> in the <literal>plc</literal>
      category is referred to canonically as
      <envar>PLC_SLICE_PREFIX</envar>.</para>

      <para>The reason for this convention is that during MyPLC
      startup, <filename>plc_config.xml</filename> is translated into
      several different languages&mdash;shell, PHP, and
      Python&mdash;so that scripts written in each of these languages
      can refer to the same underlying configuration. Most MyPLC
      scripts are written in shell, so the convention for shell
      variables predominates.</para>

      <para>The variables that you should change immediately are:</para>

      <itemizedlist>
        <listitem><para><envar>PLC_NAME</envar>: Change this to the
        name of your PLC installation.</para></listitem>
        <listitem><para><envar>PLC_ROOT_PASSWORD</envar>: Change this
        to a more secure password.</para></listitem>

        <listitem><para><envar>PLC_MAIL_SUPPORT_ADDRESS</envar>:
        Change this to the e-mail address at which you would like to
        receive support requests.</para></listitem>

        <listitem><para><envar>PLC_DB_HOST</envar>,
        <envar>PLC_DB_IP</envar>, <envar>PLC_API_HOST</envar>,
        <envar>PLC_API_IP</envar>, <envar>PLC_WWW_HOST</envar>,
        <envar>PLC_WWW_IP</envar>, <envar>PLC_BOOT_HOST</envar>,
        <envar>PLC_BOOT_IP</envar>: Change all of these to the
        preferred FQDN and external IP address of your host
        system.</para></listitem>
      </itemizedlist>

      <para> After changing these variables,
      save the file, then restart MyPLC with <command>service plc
      start</command>. You should notice that the password of the
      default administrator account is no longer
      <literal>root</literal>, and that the default site name includes
      the name of your PLC installation instead of PlanetLab. As a
      side effect of these changes, the ISO images for the boot CDs
      now have new names, so that you can freely remove the ones names
      after 'PlanetLab Test', which is the default value of
      <envar>PLC_NAME</envar> </para> 
      </section>

      <section> <title> Login as a real user </title>

      <para>Now that myplc is up and running, you can connect to the
      web site that by default runs on port 80. You can either
      directly use the default administrator user that you configured
      in <envar>PLC_ROOT_USER</envar> and
      <envar>PLC_ROOT_PASSWORD</envar>, or create a real user through
      the 'Joining' tab. Do not forget to  select both PI and tech
      roles, and to select the only site created at this stage.
      Login as the administrator to enable this user, then login as
      the real user.</para>
      </section>

    <section>
      <title>Installing nodes</title>

      <para>Install your first node by clicking <literal>Add
      Node</literal> under the <literal>Nodes</literal> tab. Fill in
      all the appropriate details, then click
      <literal>Add</literal>. Download the node's configuration file
      by clicking <literal>Download configuration file</literal> on
      the <emphasis role="bold">Node Details</emphasis> page for the
      node. Save it to a floppy disk or USB key as detailed in <xref
      linkend="TechsGuide" />.</para>

      <para>Follow the rest of the instructions in <xref
      linkend="TechsGuide" /> for creating a Boot CD and installing
      the node, except download the Boot CD image from the
      <filename>/download</filename> directory of your PLC
      installation, not from PlanetLab Central. The images located
      here are customized for your installation. If you change the
      hostname of your boot server (<envar>PLC_BOOT_HOST</envar>), or
      if the SSL certificate of your boot server expires, MyPLC will
      regenerate it and rebuild the Boot CD with the new
      certificate. If this occurs, you must replace all Boot CDs
      created before the certificate was regenerated.</para>

      <para>The installation process for a node has significantly
      improved since PlanetLab 3.3. It should now take only a few
      seconds for a new node to become ready to create slices.</para>
    </section>

    <section>
      <title>Administering nodes</title>

      <para>You may administer nodes as <literal>root</literal> by
      using the SSH key stored in
      <filename>/etc/planetlab/root_ssh_key.rsa</filename>.</para>

      <example>
        <title>Accessing nodes via SSH. Replace
        <literal>node</literal> with the hostname of the node.</title>

        <programlisting>ssh -i /etc/planetlab/root_ssh_key.rsa root@node</programlisting>
      </example>

      <para>Besides the standard Linux log files located in
      <filename>/var/log</filename>, several other files can give you
      clues about any problems with active processes:</para>

      <itemizedlist>
        <listitem><para><filename>/var/log/pl_nm</filename>: The log
        file for the Node Manager.</para></listitem>

        <listitem><para><filename>/vservers/pl_conf/var/log/pl_conf</filename>:
        The log file for the Slice Creation Service.</para></listitem>

        <listitem><para><filename>/var/log/propd</filename>: The log
        file for Proper, the service which allows certain slices to
        perform certain privileged operations in the root
        context.</para></listitem>

        <listitem><para><filename>/vservers/pl_netflow/var/log/netflow.log</filename>:
        The log file for PlanetFlow, the network traffic auditing
        service.</para></listitem>
      </itemizedlist>
    </section>

    <section>
      <title>Creating a slice</title>

      <para>Create a slice by clicking <literal>Create Slice</literal>
      under the <literal>Slices</literal> tab. Fill in all the
      appropriate details, then click <literal>Create</literal>. Add
      nodes to the slice by clicking <literal>Manage Nodes</literal>
      on the <emphasis role="bold">Slice Details</emphasis> page for
      the slice.</para>

      <para>A <command>cron</command> job runs every five minutes and
      updates the file
      <filename>/plc/data/var/www/html/xml/slices-0.5.xml</filename>
      with information about current slice state. The Slice Creation
      Service running on every node polls this file every ten minutes
      to determine if it needs to create or delete any slices. You may
      accelerate this process manually if desired.</para>

      <example>
        <title>Forcing slice creation on a node.</title>

        <programlisting><![CDATA[# Update slices.xml immediately
service plc start crond

# Kick the Slice Creation Service on a particular node.
ssh -i /etc/planetlab/root_ssh_key.rsa root@node \
vserver pl_conf exec service pl_conf restart]]></programlisting>
      </example>
    </section>

  <section id="StartupSequence">
    <title>Understanding the startup sequence</title>

    <para>During service startup described in <xref
    linkend="QuickStart" />, observe the output of this command for
    any failures. If no failures occur, you should see output similar
    to the following:</para>

    <example>
      <title>A successful MyPLC startup.</title>

      <programlisting><![CDATA[Mounting PLC:                                              [  OK  ]
PLC: Generating network files:                             [  OK  ]
PLC: Starting system logger:                               [  OK  ]
PLC: Starting database server:                             [  OK  ]
PLC: Generating SSL certificates:                          [  OK  ]
PLC: Configuring the API:                                  [  OK  ]
PLC: Updating GPG keys:                                    [  OK  ]
PLC: Generating SSH keys:                                  [  OK  ]
PLC: Starting web server:                                  [  OK  ]
PLC: Bootstrapping the database:                           [  OK  ]
PLC: Starting DNS server:                                  [  OK  ]
PLC: Starting crond:                                       [  OK  ]
PLC: Rebuilding Boot CD:                                   [  OK  ]
PLC: Rebuilding Boot Manager:                              [  OK  ]
PLC: Signing node packages:                                [  OK  ]
]]></programlisting>
    </example>

    <para>If <filename>/plc/root</filename> is mounted successfully, a
    complete log file of the startup process may be found at
    <filename>/plc/root/var/log/boot.log</filename>. Possible reasons
    for failure of each step include:</para>

    <itemizedlist>
      <listitem><para><literal>Mounting PLC</literal>: If this step
      fails, first ensure that you started MyPLC as root. Check
      <filename>/etc/sysconfig/plc</filename> to ensure that
      <envar>PLC_ROOT</envar> and <envar>PLC_DATA</envar> refer to the
      right locations. You may also have too many existing loopback
      mounts, or your kernel may not support loopback mounting, bind
      mounting, or the ext3 filesystem. Try freeing at least one
      loopback device, or re-compiling your kernel to support loopback
      mounting, bind mounting, and the ext3 filesystem. If you see an
      error similar to <literal>Permission denied while trying to open
      /plc/root.img</literal>, then SELinux may be enabled. See <xref
      linkend="Requirements" /> above for details.</para></listitem>

      <listitem><para><literal>Starting database server</literal>: If
      this step fails, check
      <filename>/plc/root/var/log/pgsql</filename> and
      <filename>/plc/root/var/log/boot.log</filename>. The most common
      reason for failure is that the default PostgreSQL port, TCP port
      5432, is already in use. Check that you are not running a
      PostgreSQL server on the host system.</para></listitem>

      <listitem><para><literal>Starting web server</literal>: If this
      step fails, check
      <filename>/plc/root/var/log/httpd/error_log</filename> and
      <filename>/plc/root/var/log/boot.log</filename> for obvious
      errors. The most common reason for failure is that the default
      web ports, TCP ports 80 and 443, are already in use. Check that
      you are not running a web server on the host
      system.</para></listitem>

      <listitem><para><literal>Bootstrapping the database</literal>:
      If this step fails, it is likely that the previous step
      (<literal>Starting web server</literal>) also failed. Another
      reason that it could fail is if <envar>PLC_API_HOST</envar> (see
      <xref linkend="Configuration" />) does not resolve to
      the host on which the API server has been enabled. By default,
      all services, including the API server, are enabled and run on
      the same host, so check that <envar>PLC_API_HOST</envar> is
      either <filename>localhost</filename> or resolves to a local IP
      address.</para></listitem>

      <listitem><para><literal>Starting crond</literal>: If this step
      fails, it is likely that the previous steps (<literal>Starting
      web server</literal> and <literal>Bootstrapping the
      database</literal>) also failed. If not, check
      <filename>/plc/root/var/log/boot.log</filename> for obvious
      errors. This step starts the <command>cron</command> service and
      generates the initial set of XML files that the Slice Creation
      Service uses to determine slice state.</para></listitem>
    </itemizedlist>

    <para>If no failures occur, then MyPLC should be active with a
    default configuration. Open a web browser on the host system and
    visit <literal>http://localhost/</literal>, which should bring you
    to the front page of your PLC installation. The password of the
    default administrator account
    <literal>root@localhost.localdomain</literal> (set by
    <envar>PLC_ROOT_USER</envar>) is <literal>root</literal> (set by
    <envar>PLC_ROOT_PASSWORD</envar>).</para>
    </section>

    <section id="FilesInvolvedRuntime"> <title> Files and directories
    involved in <emphasis>myplc</emphasis></title>
    <para>MyPLC installs the following files and directories:</para>

    <orderedlist>

      <listitem><para><filename>/plc/root.img</filename>: The main
      root filesystem of the MyPLC application. This file is an
      uncompressed ext3 filesystem that is loopback mounted on
      <filename>/plc/root</filename> when MyPLC starts. This
      filesystem, even when mounted, should be treated as an opaque
      binary that can and will be replaced in its entirety by any
      upgrade of MyPLC.</para></listitem>

      <listitem><para><filename>/plc/root</filename>: The mount point
      for <filename>/plc/root.img</filename>. Once the root filesystem
      is mounted, all MyPLC services run in a
      <command>chroot</command> jail based in this
      directory.</para></listitem>

      <listitem>
        <para><filename>/plc/data</filename>: The directory where user
        data and generated files are stored. This directory is bind
        mounted onto <filename>/plc/root/data</filename> so that it is
        accessible as <filename>/data</filename> from within the
        <command>chroot</command> jail. Files in this directory are
        marked with <command>%config(noreplace)</command> in the
        RPM. That is, during an upgrade of MyPLC, if a file has not
        changed since the last installation or upgrade of MyPLC, it is
        subject to upgrade and replacement. If the file has changed,
        the new version of the file will be created with a
        <filename>.rpmnew</filename> extension. Symlinks within the
        MyPLC root filesystem ensure that the following directories
        (relative to <filename>/plc/root</filename>) are stored
        outside the MyPLC filesystem image:</para>

        <itemizedlist>
          <listitem><para><filename>/etc/planetlab</filename>: This
          directory contains the configuration files, keys, and
          certificates that define your MyPLC
          installation.</para></listitem>

          <listitem><para><filename>/var/lib/pgsql</filename>: This
          directory contains PostgreSQL database
          files.</para></listitem>

          <listitem><para><filename>/var/www/html/alpina-logs</filename>: This
          directory contains node installation logs.</para></listitem>

          <listitem><para><filename>/var/www/html/boot</filename>: This
          directory contains the Boot Manager, customized for your MyPLC
          installation, and its data files.</para></listitem>

          <listitem><para><filename>/var/www/html/download</filename>: This
          directory contains Boot CD images, customized for your MyPLC
          installation.</para></listitem>

          <listitem><para><filename>/var/www/html/install-rpms</filename>: This
          directory is where you should install node package updates,
          if any. By default, nodes are installed from the tarball
          located at
          <filename>/var/www/html/boot/PlanetLab-Bootstrap.tar.bz2</filename>,
          which is pre-built from the latest PlanetLab Central
          sources, and installed as part of your MyPLC
          installation. However, nodes will attempt to install any
          newer RPMs located in
          <filename>/var/www/html/install-rpms/planetlab</filename>,
          after initial installation and periodically thereafter. You
          must run <command>yum-arch</command> and
          <command>createrepo</command> to update the
          <command>yum</command> caches in this directory after
          installing a new RPM. PlanetLab Central cannot support any
          changes to this directory.</para></listitem>

          <listitem><para><filename>/var/www/html/xml</filename>: This
          directory contains various XML files that the Slice Creation
          Service uses to determine the state of slices. These XML
          files are refreshed periodically by <command>cron</command>
          jobs running in the MyPLC root.</para></listitem>
        </itemizedlist>
      </listitem>

      <listitem id="MyplcInitScripts">
        <para><filename>/etc/init.d/plc</filename>: This file
        is a System V init script installed on your host filesystem,
        that allows you to start up and shut down MyPLC with a single
        command, as described in <xref linkend="QuickStart" />.</para>
      </listitem>

      <listitem><para><filename>/etc/sysconfig/plc</filename>: This
      file is a shell script fragment that defines the variables
      <envar>PLC_ROOT</envar> and <envar>PLC_DATA</envar>. By default,
      the values of these variables are <filename>/plc/root</filename>
      and <filename>/plc/data</filename>, respectively. If you wish,
      you may move your MyPLC installation to another location on your
      host filesystem and edit the values of these variables
      appropriately, but you will break the RPM upgrade
      process. PlanetLab Central cannot support any changes to this
      file.</para></listitem>

      <listitem><para><filename>/etc/planetlab</filename>: This
      symlink to <filename>/plc/data/etc/planetlab</filename> is
      installed on the host system for convenience.</para></listitem>
    </orderedlist>
  </section>
  </section>

  <section id="DevelopmentEnvironment">
    <title>Rebuilding and customizing MyPLC</title>

    <para>The MyPLC package, though distributed as an RPM, is not a
    traditional package that can be easily rebuilt from SRPM. The
    requisite build environment is quite extensive and numerous
    assumptions are made throughout the PlanetLab source code base,
    that the build environment is based on Fedora Core 4 and that
    access to a complete Fedora Core 4 mirror is available.</para>

    <para>For this reason, it is recommended that you only rebuild
    MyPLC (or any of its components) from within the MyPLC development
    environment. The MyPLC development environment is similar to MyPLC
    itself in that it is a portable filesystem contained within a
    <command>chroot</command> jail. The filesystem contains all the
    necessary tools required to rebuild MyPLC, as well as a snapshot
    of the PlanetLab source code base in the form of a local CVS
    repository.</para>

    <section>
      <title>Installation</title>

      <para>Install the MyPLC development environment similarly to how
      you would install MyPLC. You may install both packages on the same
      host system if you wish. As with MyPLC, the MyPLC development
      environment should be treated as a monolithic software
      application, and any files present in the
      <command>chroot</command> jail should not be modified directly, as
      they are subject to upgrade.</para>

      <itemizedlist>
      <listitem> <para>If your distribution supports RPM:</para>
      <programlisting><![CDATA[# rpm -U http://build.planet-lab.org/build/myplc-0_4-rc2/RPMS/i386/myplc-devel-0.4-2.planetlab.i386.rpm]]></programlisting></listitem>

      <listitem> <para>If your distribution does not support RPM:</para>
<programlisting><![CDATA[# cd /tmp
# wget http://build.planet-lab.org/build/myplc-0_4-rc2/RPMS/i386/myplc-devel-0.4-2.planetlab.i386.rpm
# cd /
# rpm2cpio /tmp/myplc-devel-0.4-2.planetlab.i386.rpm | cpio -diu]]></programlisting></listitem>
    </itemizedlist>
    </section>

    <section>
      <title>Configuration</title> 
      
      <para> The default configuration should work as-is on most
      sites. Configuring the development package can be achieved in a
      similar way as for <emphasis>myplc</emphasis>, as described in
      <xref linkend="Configuration"
      />. <command>plc-config-tty</command> supports a
      <emphasis>-d</emphasis> option for supporting the
      <emphasis>myplc-devel</emphasis> case, that can be useful in a
      context where it would not guess it by itself.  Refer to <xref
      linkend="VariablesDevel" /> for a list of variables.</para>
      </section>

    <section id="FilesInvolvedDevel"> <title> Files and directories
    involved in <emphasis>myplc-devl</emphasis></title>

      <para>The MyPLC development environment installs the following
      files and directories:</para>

      <itemizedlist>
        <listitem><para><filename>/plc/devel/root.img</filename>: The
        main root filesystem of the MyPLC development environment. This
        file is an uncompressed ext3 filesystem that is loopback mounted
        on <filename>/plc/devel/root</filename> when the MyPLC
        development environment is initialized. This filesystem, even
        when mounted, should be treated as an opaque binary that can and
        will be replaced in its entirety by any upgrade of the MyPLC
        development environment.</para></listitem>

        <listitem><para><filename>/plc/devel/root</filename>: The mount
        point for
        <filename>/plc/devel/root.img</filename>.</para></listitem>

        <listitem>
          <para><filename>/plc/devel/data</filename>: The directory
          where user data and generated files are stored. This directory
          is bind mounted onto <filename>/plc/devel/root/data</filename>
          so that it is accessible as <filename>/data</filename> from
          within the <command>chroot</command> jail. Files in this
          directory are marked with
          <command>%config(noreplace)</command> in the RPM. Symlinks
          ensure that the following directories (relative to
          <filename>/plc/devel/root</filename>) are stored outside the
          root filesystem image:</para>

          <itemizedlist>
            <listitem><para><filename>/etc/planetlab</filename>: This
            directory contains the configuration files that define your
            MyPLC development environment.</para></listitem>
            
            <listitem><para><filename>/cvs</filename>: A
            snapshot of the PlanetLab source code is stored as a CVS
            repository in this directory. Files in this directory will
            <emphasis role="bold">not</emphasis> be updated by an upgrade of
            <filename>myplc-devel</filename>. See <xref
            linkend="UpdatingCVS" /> for more information about updating
            PlanetLab source code.</para></listitem>

            <listitem><para><filename>/build</filename>:
            Builds are stored in this directory. This directory is bind
            mounted onto <filename>/plc/devel/root/build</filename> so that
            it is accessible as <filename>/build</filename> from within the
            <command>chroot</command> jail. The build scripts in this
            directory are themselves source controlled; see <xref
            linkend="BuildingMyPLC" /> for more information about executing
            builds.</para></listitem>
          </itemizedlist>
        </listitem>

        <listitem>
          <para><filename>/etc/init.d/plc-devel</filename>: This file is
          a System V init script installed on your host filesystem, that
          allows you to start up and shut down the MyPLC development
          environment with a single command.</para>
        </listitem>
      </itemizedlist>
    </section>

    <section>
      <title>Fedora Core 4 mirror requirement</title>

      <para>The MyPLC development environment requires access to a
      complete Fedora Core 4 i386 RPM repository, because several
      different filesystems based upon Fedora Core 4 are constructed
      during the process of building MyPLC. You may configure the
      location of this repository via the
      <envar>PLC_DEVEL_FEDORA_URL</envar> variable in
      <filename>/plc/devel/data/etc/planetlab/plc_config.xml</filename>. The
      value of the variable should be a URL that points to the top
      level of a Fedora mirror that provides the
      <filename>base</filename>, <filename>updates</filename>, and
      <filename>extras</filename> repositories, e.g.,</para>

      <itemizedlist>
        <listitem><para><filename>file:///data/fedora</filename></para></listitem>
        <listitem><para><filename>http://coblitz.planet-lab.org/pub/fedora</filename></para></listitem>
        <listitem><para><filename>ftp://mirror.cs.princeton.edu/pub/mirrors/fedora</filename></para></listitem>
        <listitem><para><filename>ftp://mirror.stanford.edu/pub/mirrors/fedora</filename></para></listitem>
        <listitem><para><filename>http://rpmfind.net/linux/fedora</filename></para></listitem>
      </itemizedlist>

      <para>As implied by the list, the repository may be located on
      the local filesystem, or it may be located on a remote FTP or
      HTTP server. URLs beginning with <filename>file://</filename>
      should exist at the specified location relative to the root of
      the <command>chroot</command> jail. For optimum performance and
      reproducibility, specify
      <envar>PLC_DEVEL_FEDORA_URL=file:///data/fedora</envar> and
      download all Fedora Core 4 RPMS into
      <filename>/plc/devel/data/fedora</filename> on the host system
      after installing <filename>myplc-devel</filename>. Use a tool
      such as <command>wget</command> or <command>rsync</command> to
      download the RPMS from a public mirror:</para>

      <example>
        <title>Setting up a local Fedora Core 4 repository.</title>
        
        <programlisting><![CDATA[# mkdir -p /plc/devel/data/fedora
# cd /plc/devel/data/fedora

# for repo in core/4/i386/os core/updates/4/i386 extras/4/i386 ; do
>     wget -m -nH --cut-dirs=3 http://coblitz.planet-lab.org/pub/fedora/linux/$repo
> done]]></programlisting>
      </example>
      
      <para>Change the repository URI and <command>--cut-dirs</command>
      level as needed to produce a hierarchy that resembles:</para>

      <programlisting><![CDATA[/plc/devel/data/fedora/core/4/i386/os
/plc/devel/data/fedora/core/updates/4/i386
/plc/devel/data/fedora/extras/4/i386]]></programlisting>

      <para>A list of additional Fedora Core 4 mirrors is available at
      <ulink url="http://fedora.redhat.com/Download/mirrors.html">http://fedora.redhat.com/Download/mirrors.html</ulink>.</para>
    </section>

    <section id="BuildingMyPLC">
      <title>Building MyPLC</title>

      <para>All PlanetLab source code modules are built and installed
      as RPMS. A set of build scripts, checked into the
      <filename>build/</filename> directory of the PlanetLab CVS
      repository, eases the task of rebuilding PlanetLab source
      code.</para>

      <para> Before you try building MyPLC, you might check the
      configuration, in a file named
      <emphasis>plc_config.xml</emphasis> that relies on a very
      similar model as MyPLC, located in
      <emphasis>/etc/planetlab</emphasis> within the chroot jail, or
      in <emphasis>/plc/devel/data/etc/planetlab</emphasis> from the
      root context. The set of applicable variables is described in
      <xref linkend="VariablesDevel" />. </para>

      <para>To build MyPLC, or any PlanetLab source code module, from
      within the MyPLC development environment, execute the following
      commands as root:</para>

      <example>
        <title>Building MyPLC.</title>
        
        <programlisting><![CDATA[# Initialize MyPLC development environment
service plc-devel start

# Enter development environment
chroot /plc/devel/root su -

# Check out build scripts into a directory named after the current
# date. This is simply a convention, it need not be followed
# exactly. See build/build.sh for an example of a build script that
# names build directories after CVS tags.
DATE=$(date +%Y.%m.%d)
cd /build
cvs -d /cvs checkout -d $DATE build

# Build everything
make -C $DATE]]></programlisting>
      </example>

      <para>If the build succeeds, a set of binary RPMS will be
      installed under
      <filename>/plc/devel/data/build/$DATE/RPMS/</filename> that you
      may copy to the
      <filename>/var/www/html/install-rpms/planetlab</filename>
      directory of your MyPLC installation (see <xref
      linkend="Installation" />).</para>
    </section>

    <section id="UpdatingCVS">
      <title>Updating CVS</title>

      <para>A complete snapshot of the PlanetLab source code is included
      with the MyPLC development environment as a CVS repository in
      <filename>/plc/devel/data/cvs</filename>. This CVS repository may
      be accessed like any other CVS repository. It may be accessed
      using an interface such as <ulink
      url="http://www.freebsd.org/projects/cvsweb.html">CVSweb</ulink>,
      and file permissions may be altered to allow for fine-grained
      access control. Although the files are included with the
      <filename>myplc-devel</filename> RPM, they are <emphasis
      role="bold">not</emphasis> subject to upgrade once installed. New
      versions of the <filename>myplc-devel</filename> RPM will install
      updated snapshot repositories in
      <filename>/plc/devel/data/cvs-%{version}-%{release}</filename>,
      where <literal>%{version}-%{release}</literal> is replaced with
      the version number of the RPM.</para>

      <para>Because the CVS repository is not automatically upgraded,
      if you wish to keep your local repository synchronized with the
      public PlanetLab repository, it is highly recommended that you
      use CVS's support for <ulink
      url="http://ximbiot.com/cvs/wiki/index.php?title=CVS--Concurrent_Versions_System_v1.12.12.1:_Tracking_third-party_sources">vendor
      branches</ulink> to track changes. Vendor branches ease the task
      of merging upstream changes with your local modifications. To
      import a new snapshot into your local repository (for example,
      if you have just upgraded from
      <filename>myplc-devel-0.4-2</filename> to
      <filename>myplc-devel-0.4-3</filename> and you notice the new
      repository in <filename>/plc/devel/data/cvs-0.4-3</filename>),
      execute the following commands as root from within the MyPLC
      development environment:</para>

      <example>
        <title>Updating /data/cvs from /data/cvs-0.4-3.</title>
        
        <para><emphasis role="bold">Warning</emphasis>: This may cause
        severe, irreversible changes to be made to your local
        repository. Always tag your local repository before
        importing.</para>

        <programlisting><![CDATA[# Initialize MyPLC development environment
service plc-devel start

# Enter development environment
chroot /plc/devel/root su -

# Tag current state
cvs -d /cvs rtag before-myplc-0_4-3-merge

# Export snapshot
TMP=$(mktemp -d /data/export.XXXXXX)
pushd $TMP
cvs -d /data/cvs-0.4-3 export -r HEAD .
cvs -d /cvs import -m "PlanetLab sources from myplc-0.4-3" -ko -I ! . planetlab myplc-0_4-3
popd
rm -rf $TMP]]></programlisting>
      </example>

      <para>If there any merge conflicts, use the command suggested by
      CVS to help the merge. Explaining how to fix merge conflicts is
      beyond the scope of this document; consult the CVS documentation
      for more information on how to use CVS.</para>
    </section>
  </section>

  <appendix id="VariablesRuntime">
    <title>Configuration variables (for <emphasis>myplc</emphasis>)</title>

    <para>Listed below is the set of standard configuration variables
    and their default values, defined in the template
    <filename>/etc/planetlab/default_config.xml</filename>. Additional
    variables and their defaults may be defined in site-specific XML
    templates that should be placed in
    <filename>/etc/planetlab/configs/</filename>.</para>

    <para>This information is available online within
    <command>plc-config-tty</command>, e.g.:</para>

<example><title>Advanced usage of plc-config-tty</title>
<programlisting><![CDATA[<plc> # plc-config-tty
Enter command (u for usual changes, w to save, ? for help) V plc_dns
========== Category = PLC_DNS
### Enable DNS
# Enable the internal DNS server. The server does not provide reverse
# resolution and is not a production quality or scalable DNS solution.
# Use the internal DNS server only for small deployments or for testing.
PLC_DNS_ENABLED
]]></programlisting></example>


  <para> List of the <command>myplc</command> configuration variables:</para>
   &Variables;
  </appendix>

  <appendix id="VariablesDevel">
    <title>Development configuration variables (for <emphasis>myplc-devel</emphasis>)</title>

    &DevelVariables;
  </appendix>

  <bibliography>
    <title>Bibliography</title>

    <biblioentry id="TechsGuide">
      <author><firstname>Mark</firstname><surname>Huang</surname></author>
      <title><ulink
      url="http://www.planet-lab.org/doc/TechsGuide.php">PlanetLab
      Technical Contact's Guide</ulink></title>
    </biblioentry>
  </bibliography>
</article>