path: root/gnome2-system-admin-guide/C/gconf.xml

<?xml version="1.0" encoding="utf-8"?>
<chapter id="gconf-0">
  <title>Using GConf</title>
  <highlights>
    <para>The information in this chapter describes how to use <application>GConf</application> to manage user preferences.</para>
  </highlights>
  <sect1 id="gconf-1">
    <title>Introducing GConf</title>
    <indexterm>
      <primary>GConf</primary>
      <secondary>introduction</secondary>
    </indexterm>
    <para><application>GConf</application> simplifies the administration of preferences
for users in the GNOME desktop environment. <application>GConf</application>
enables system administrators to do the following:</para>
    <itemizedlist>
      <listitem>
        <para>Set mandatory values for particular preferences for all users.
In this way, system administrators can control whether users can update particular
preferences.</para>
      </listitem>
      <listitem>
        <para>Set default values for particular preferences for all users. </para>
      </listitem>
      <listitem>
        <para>Use suggested values for preferences that are specified in
definition files for the preferences.</para>
      </listitem>
      <listitem>
        <para>Read documentation on each preference. </para>
      </listitem>
    </itemizedlist>
    <para><application>GConf</application> also notifies applications when a preference
value changes, locally or across a network. In this way, when you change a
preference, all applications that use the preference are immediately updated.</para>
    <para><application>GConf</application> has the following components: </para>
    <itemizedlist>
      <listitem>
        <para>A repository of user preferences. </para>
      </listitem>
      <listitem>
        <para>A daemon, <command>gconfd-2</command>.</para>
      </listitem>
      <listitem>
        <para>A command line tool, <command>gconftool-2</command>.</para>
      </listitem>
    </itemizedlist>
  </sect1>
  <sect1 id="gconf-24">
    <title>GConf Repository</title>
    <indexterm>
      <primary>GConf</primary>
      <secondary>repository</secondary>
    </indexterm>
    <para>Each preference in the <application>GConf</application> repository is
expressed as a key-value pair. A <firstterm>GConf preference key</firstterm>
is an element in the repository that corresponds to an application preference.
For example, the <literal>/apps/gnome-session/options/show_splash_screen</literal>
preference key corresponds to the <guilabel>Show splash screen on login</guilabel>
option in the <application>Sessions</application> preference tool.  The GNOME
user interface does not contain all of the preference keys in the <application>GConf</application> repository. For example, the <application>Sessions</application>
preference tool does not contain an option that corresponds to the <literal>/apps/gnome-session/options/splash_screen_text</literal> key.</para>
    <para>The repository is structured like a simple hierarchical file system.
The repository contains the following:</para>
    <itemizedlist>
      <listitem>
        <para>Directories that correspond to applications that use the <application>GConf</application> repository. For example, the file system contains the
directory <filename>/apps/metacity</filename>. </para>
      </listitem>
      <listitem>
        <para>Subdirectories that correspond to categories of preferences.
For example, the file system contains the directory <filename>/apps/metacity/general</filename>.</para>
      </listitem>
      <listitem>
        <para>Special files that list the preference keys in the directory,
and contain information about the keys. For example, a file that contains
information about the keys that relate to the HTTP proxy preferences is in
the directory <filename>/system/http_proxy</filename>. </para>
      </listitem>
      <listitem>
        <para>A <filename>/schemas</filename> directory that contains files
that describe all of the preference keys.</para>
      </listitem>
    </itemizedlist>
    <para>Preference keys typically have simple values such as strings, integers,
or lists of strings and integers. The format of the preference key in the
repository depends on the backend module that is used to read the repository.
The following is an example of the <literal>/desktop/gnome/interface/font_name</literal> preference key when an Extensible Markup Language (XML) backend
module is used to read the repository:</para>
    <literallayout>&lt;entry name=&quot;font_name&quot; mtime=&quot;1038323555&quot; muser=&quot;user123&quot; type=&quot;string&quot;&gt;
&lt;stringvalue&gt;avantgarde 10&lt;/stringvalue&gt;&lt;/entry&gt;</literallayout>
    <note>
      <para>When this guide refers to a preference key, the path to the key
is added to the name of the key. For example, the <literal>font_name</literal>
preference key in the <filename>/desktop/gnome/interface</filename> subdirectory
is referred to as <literal>/desktop/gnome/interface/font_name</literal>.</para>
    </note>
    <sect2 id="gconf-26">
      <title>GConf Configuration Sources</title>
      <indexterm>
        <primary>GConf</primary>
        <secondary>configuration sources</secondary>
      </indexterm>
      <para>The <application>GConf</application> repository contains
a series of storage locations that are called <firstterm>configuration sources</firstterm>. The configuration sources are listed in the <firstterm>GConf
path file</firstterm>. The location of the <application>GConf</application>
path file is <filename>/etc/gconf/<replaceable>version_number</replaceable>/path</filename>. Each user has a path file. Each line in the path file specifies
the following information:</para>
      <itemizedlist>
        <listitem>
          <para>The backend module to use to read the repository. </para>
        </listitem>
        <listitem>
          <para>The permissions on the repository.</para>
        </listitem>
        <listitem>
          <para>The location of the repository.</para>
        </listitem>
      </itemizedlist>
      <para>By default, the contents of the <application>GConf</application> path
file are as follows: </para>
      <literallayout>xml:readonly:/etc/gconf/gconf.xml.mandatory
include &quot;$(HOME)/.gconf.path&quot;
xml:readwrite:$(HOME)/.gconf
xml:readonly:/etc/gconf/gconf.xml.defaults</literallayout>
      <para>When <application>GConf</application> searches for a preference value, <application>GConf</application> reads the configuration sources in the order specified
in the path file. The following table describes the configuration sources
in the path file:</para>
      <informaltable frame="topbot">
        <tgroup cols="2" colsep="0" rowsep="0">
          <colspec colwidth="31.29*"/>
          <colspec colwidth="68.71*"/>
          <thead>
            <row rowsep="1">
              <entry valign="top">
                <para>Configuration Source</para>
              </entry>
              <entry valign="top">
                <para>Description</para>
              </entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry valign="top">
                <para>Mandatory</para>
              </entry>
              <entry valign="top">
                <para>The permissions on this configuration source are set to read only. Users cannot
overwrite the values in this source, so the preferences in the source are
mandatory.</para>
              </entry>
            </row>
            <row>
              <entry valign="top">
                <para>User</para>
              </entry>
              <entry valign="top">
                <para>This configuration source is stored in the <filename>.gconf</filename> directory
in the home directory of the user. When the user sets a preference, the new
preference information is added to this location. </para>
              </entry>
            </row>
            <row>
              <entry valign="top">
                <para>Default</para>
              </entry>
              <entry valign="top">
                <para>This configuration source contains the default preference settings.</para>
              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>
      <para>The sequence of the configuration sources in the path file ensures that
mandatory preference settings override user preference settings. The sequence
also ensures that user preference settings override default preference settings.
That is, <application>GConf</application> applies preferences in the following
order of priority:</para>
      <orderedlist>
        <listitem>
          <para>Mandatory preferences </para>
        </listitem>
        <listitem>
          <para>User-specified preferences </para>
        </listitem>
        <listitem>
          <para>Default preferences</para>
        </listitem>
      </orderedlist>
      <para>The <literal>include</literal> instruction in the <application>GConf</application> path file enables users to use another configuration source.
To use another configuration source, the user must specify the location of
the configuration source. The user specifies the location of the configuration
source in the home directory, in a file that is called <filename>.gconf.path</filename>.</para>
    </sect2>
    <sect2 id="gconf-27">
      <title>GConf Schemas</title>
      <indexterm>
        <primary>GConf</primary>
        <secondary>schemas</secondary>
      </indexterm>
      <indexterm>
        <primary>GConf</primary>
        <secondary>schema keys</secondary>
      </indexterm>
      <indexterm>
        <primary>GConf</primary>
        <secondary>schema objects</secondary>
      </indexterm>
      <indexterm>
        <primary>schemas</primary>
        <secondary>description</secondary>
      </indexterm>
      <indexterm>
        <primary>schemas</primary>
        <secondary>schema keys</secondary>
      </indexterm>
      <indexterm>
        <primary>schemas</primary>
        <secondary>schema objects</secondary>
      </indexterm>
      <para>A <firstterm>GConf schema</firstterm> is a collective term
for a <firstterm>GConf schema key</firstterm> and a <firstterm>GConf schema
object</firstterm>. The following table describes schema keys and schema objects
and the relationship of these items to preference keys:</para>
      <informaltable frame="topbot">
        <tgroup cols="2" colsep="0" rowsep="0">
          <colspec colname="colspec0" colwidth="24.31*"/>
          <colspec colname="colspec1" colwidth="75.69*"/>
          <thead>
            <row rowsep="1">
              <entry valign="top">
                <para>Item</para>
              </entry>
              <entry valign="top">
                <para>Description</para>
              </entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry colname="colspec0" valign="top">
                <para>Preference key</para>
              </entry>
              <entry colname="colspec1" valign="top">
                <para>An element in the <application>GConf</application> repository that corresponds to an application preference.</para>
              </entry>
            </row>
            <row>
              <entry valign="top">
                <para>Schema key</para>
              </entry>
              <entry valign="top">
                <para>A key that stores a schema object for a preference key. </para>
              </entry>
            </row>
            <row>
              <entry valign="top">
                <para>Schema object</para>
              </entry>
              <entry valign="top">
                <para>An element in a configuration source that contains information for a preference
key, such as the following:</para>
                <itemizedlist>
                  <listitem>
                    <para>The name of the application that uses the preference key.</para>
                  </listitem>
                  <listitem>
                    <para>The type of value required for the preference key, for example
integer, boolean, and so on.</para>
                  </listitem>
                  <listitem>
                    <para>A default value for the preference key. </para>
                  </listitem>
                  <listitem>
                    <para>Brief documentation on the preference key.</para>
                  </listitem>
                </itemizedlist>
              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>
      <para>The following table gives examples of a preference key, a schema key,
and a schema object:</para>
      <informaltable frame="topbot">
        <tgroup cols="2" colsep="0" rowsep="0">
          <colspec colname="colspec0" colwidth="24.31*"/>
          <colspec colname="colspec1" colwidth="75.69*"/>
          <thead>
            <row rowsep="1">
              <entry valign="top">
                <para>Item</para>
              </entry>
              <entry valign="top">
                <para>Example</para>
              </entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry colname="colspec0" valign="top">
                <para>Preference key</para>
              </entry>
              <entry colname="colspec1" valign="top">
                <para>
                  <literal>/desktop/gnome/interface/font_name</literal>
                </para>
              </entry>
            </row>
            <row>
              <entry colname="colspec0" valign="top">
                <para>Schema key</para>
              </entry>
              <entry colname="colspec1" valign="top">
                <para>
                  <literal>/schemas/desktop/gnome/interface/font_name</literal>
                </para>
              </entry>
            </row>
            <row>
              <entry valign="top">
                <para>Schema object</para>
              </entry>
              <entry valign="top">
                <literallayout>&lt;schema&gt;
  &lt;applyto&gt;/desktop/gnome/interface/font_name&lt;/applyto&gt;
  &lt;key&gt;/schemas/desktop/gnome/interface/font_name&lt;/key&gt;
  &lt;owner&gt;gnome&lt;/owner&gt;
  &lt;type&gt;string&lt;/type&gt;
  &lt;default&gt;Sans 10&lt;/default&gt;
  &lt;locale name=&quot;C&quot;&gt;
    &lt;short&gt;Default font&lt;/short&gt;
      &lt;long&gt;Name of the default font used by gtk+.&lt;/long&gt;
  &lt;/locale&gt;
&lt;/schema&gt;</literallayout>
              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>
      <para>You can associate a schema key with a preference key. For example, the
following <literal>/desktop/gnome/interface/font_name</literal> key includes
a schema key:</para>
      <literallayout>&lt;entry name=&quot;font_name&quot; mtime=&quot;1034873859&quot; 
schema=&quot;/schemas/desktop/gnome/interface/font_name&quot;/&gt;</literallayout>
      <para>When you associate a schema key with a preference key, the preference
uses the suggested value that is specified in the schema object of the schema
key. The suggested value is contained in the <literal>&lt;default&gt;</literal>
element in the schema object. By default, all the preference keys in the default
configuration source are associated with schema keys.</para>
      <para>Typically, schemas are stored in the default configuration source. </para>
    </sect2>
    <sect2 id="gconf-2">
      <title>GConf Schema Definition Files</title>
      <indexterm>
        <primary>GConf</primary>
        <secondary>schema definition files</secondary>
        <tertiary>introduction</tertiary>
      </indexterm>
      <indexterm>
        <primary>schemas</primary>
        <secondary>schema definition files</secondary>
        <tertiary>introduction</tertiary>
      </indexterm>
      <para>Schemas are generated from <firstterm>schema definition
files</firstterm>. A schema definition file defines the characteristics of
all of the keys in a particular application. Schema definition files have
a <filename>.schemas</filename> extension.</para>
      <para>The schema definition files are included in the <filename>/etc/gconf/schemas</filename> directory. You can use the schema definition files to create a
new configuration source.</para>
      <para>Some schema definition files correspond closely to a part of the GNOME
user interface. For example, <filename>system_http_proxy.schemas</filename>
corresponds to the <application>Network Proxy</application> preference tool.
Other schema definition files contain preference keys that are not present
in the GNOME user interface. For example, the <literal>/apps/gnome-session/options/splash_screen_text</literal> key is not present in the user interface. </para>
      <para>Some parts of the GNOME user interface contain preferences that represent
preference keys from more than one schema definition file. For example, the <application>Keyboard Shortcuts</application> preference tool contains preferences that
represent keys from the <filename>panel-global-config.schemas</filename> and <filename>metacity.schemas</filename> files.</para>
    </sect2>
  </sect1>
  <sect1 id="gconf-25">
    <title>GConf Daemon</title>
    <indexterm>
      <primary>gconfd</primary>
      <see>GConf daemon</see>
    </indexterm>
    <indexterm>
      <primary>GConf</primary>
      <secondary>daemon</secondary>
    </indexterm>
    <para>The <application>GConf</application> daemon is called <command>gconfd-2</command>. The <application>GConf</application> daemon notifies applications when a preference value changes.
For example, you might select to show only icons in toolbars in the <application>Menus &amp; Toolbars</application> preference tool. When you select this option
in the preference tool, the toolbars on all open applications are updated
instantly. The <application>GConf</application> daemon can operate locally,
or across a network.</para>
    <para>An instance of the <application>GConf</application> daemon is started
for each user. The <application>GConf</application> daemon does not have to
deal with complex problems such as authentication and data security. When
the <application>GConf</application> daemon starts, the daemon loads the <application>GConf</application> path file. The <application>GConf</application> daemon
manages all access between applications and the configuration sources.</para>
    <para>When an application requests the value of a preference key, the daemon
searches the configuration sources as follows:</para>
    <orderedlist>
      <listitem>
        <para>Search for the value of the preference key in each configuration
source, in the order specified in the path file. If the value is found, return
the value.</para>
      </listitem>
      <listitem>
        <para>If a value is not found, search for the schema key that corresponds
to the preference key in each configuration source, in the order specified
in the path file.</para>
      </listitem>
      <listitem>
        <para>If the schema key is found, check the value of the schema
key.</para>
      </listitem>
      <listitem>
        <para>If the value of the schema key is a schema object, return
the suggested value in the <literal>&lt;default&gt;</literal> element of the
schema object.</para>
      </listitem>
    </orderedlist>
    <para>The <application>GConf</application> daemon also caches preference key
values. All applications use this cache, so applications only need to access
the configuration sources once.</para>
    <para>To terminate the <application>GConf</application> daemon, run the following
command:</para>
    <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --shutdown</userinput></para>
  </sect1>
  <sect1 id="gconf-6">
    <title>GConf Command Line Tool</title>
    <indexterm>
      <primary>gconftool-2</primary>
      <see>GConf command line tool</see>
    </indexterm>
    <indexterm>
      <primary>GConf</primary>
      <secondary>command line tool</secondary>
    </indexterm>
    <para><application>GConf</application> includes a
command line tool, <command>gconftool-2</command>. You can use the <command>gconftool&ndash;2</command> command to perform the following tasks: </para>
    <itemizedlist>
      <listitem>
        <para>Set the values of keys.</para>
      </listitem>
      <listitem>
        <para>Display the values of keys.</para>
      </listitem>
      <listitem>
        <para>Install schemas from schema definition files when you install
an application.</para>
      </listitem>
    </itemizedlist>
    <para>For example, use the following command to display the values of all
keys in the <filename>/desktop/gnome</filename> directory and subdirectories.</para>
    <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --recursive-list
/desktop/gnome</userinput></para>
    <para><xref linkend="gconf-TBL-7"/> lists some of the options that you can
use with the <command>gconftool-2</command> command.</para>
    <table frame="topbot" id="gconf-TBL-7">
      <title>gconftool-2 Command Options</title>
      <tgroup cols="2" colsep="0" rowsep="0">
        <colspec colname="colspec0" colwidth="35.52*"/>
        <colspec colname="colspec1" colwidth="64.48*"/>
        <thead>
          <row rowsep="1">
            <entry valign="top">
              <para>Option</para>
            </entry>
            <entry valign="top">
              <para>Function</para>
            </entry>
          </row>
        </thead>
        <tbody>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--all-dirs</literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Lists all subdirectories in a
directory that you specify.</para>
            </entry>
          </row>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--all-entries</literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Displays the values of all keys
in a directory that you specify.</para>
            </entry>
          </row>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--config-source=<replaceable>configuration_source</replaceable></literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Use this option with the <literal>--direct</literal> option
to specify a configuration source to use. If you do not specify a configuration
source with this option, the command runs on all configuration sources in
the path file.</para>
            </entry>
          </row>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--direct</literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Use this option with the <literal>--config-source</literal> option to access a configuration source directly.
When you use this option, <application>GConf</application> bypasses the server.
Ensure that the <application>GConf</application> daemon, <command>gconfd-2</command>, is not running before you use this option.</para>
            </entry>
          </row>
          <row>
            <entry valign="top">
              <para>
                <literal>--get</literal>
              </para>
            </entry>
            <entry valign="top">
              <para>Displays the value of a preference key that you specify.
Also displays the values of the elements in the schema object for a schema
key that you specify.</para>
            </entry>
          </row>
          <row>
            <entry valign="top">
              <para>
                <literal>--help</literal>
              </para>
            </entry>
            <entry valign="top">
              <para>Displays a help message about the <command>gconftool-2</command> command, and the options that you can use with the <command>gconftool-2</command> command.</para>
            </entry>
          </row>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--long-desc=<replaceable>description</replaceable></literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Use this option with the <literal>--set-schema</literal>
option to specify a long description for a schema key. </para>
            </entry>
          </row>
          <row>
            <entry valign="top">
              <para>
                <literal>--makefile-install-rule</literal>
              </para>
            </entry>
            <entry valign="top">
              <para>Installs schema definition files to applications.</para>
            </entry>
          </row>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--owner=<replaceable>owner</replaceable></literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Use this option with the <literal>--set-schema</literal> option to specify
an owner for a schema key. </para>
            </entry>
          </row>
          <row>
            <entry valign="top">
              <para>
                <literal>--recursive-list</literal>
              </para>
            </entry>
            <entry valign="top">
              <para>Displays the value of all preference keys in all
subdirectories in a directory that you specify.</para>
            </entry>
          </row>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--recursive-unset</literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Resets
the values of all preference keys, in all subdirectories in a directory, from
the user setting to the setting in the default configuration source.</para>
            </entry>
          </row>
          <row>
            <entry valign="top">
              <para>
                <literal>--set</literal>
              </para>
            </entry>
            <entry valign="top">
              <para>Sets the value of a preference key, and writes the value
to the user configuration source. Use the <literal>--type</literal> option
with the <literal>--set</literal> option to specify the data type of the value
that you want to set. For example, the following command sets the value of
the <literal>/apps/gnome-terminal/profiles/Default/background_color</literal>
key in the user configuration source:</para>
              <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --set  &quot;/apps/gnome-terminal/profiles/Default/background_color&quot;
--type string &quot;#000000&quot;</userinput></para>
              <para>You can also use the <literal>--direct</literal> option and the <literal>--config-source</literal> option
with the <literal>--set</literal> option to write a value to another configuration
source.</para>
            </entry>
          </row>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--set-schema</literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Sets the value of an attribute
in a schema key, and writes the value to the default configuration source.</para>
              <para>Use the following options with the <literal>--set-schema</literal>
option to specify the attribute that you want to update:</para>
              <itemizedlist>
                <listitem>
                  <para>
                    <literal>--type</literal>
                  </para>
                </listitem>
                <listitem>
                  <para>
                    <literal>--short-desc</literal>
                  </para>
                </listitem>
                <listitem>
                  <para>
                    <literal>--long-desc</literal>
                  </para>
                </listitem>
                <listitem>
                  <para>
                    <literal>--owner</literal>
                  </para>
                </listitem>
              </itemizedlist>
              <para>For example, the following command sets the short description
in the schema key for the <literal>/apps/gnome-terminal/profiles/Default/background_color</literal> key:</para>
              <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --set-schema  &quot;/schemas/apps/gnome-terminal/profiles/Default/background_color&quot;
--short-desc &quot;Default  background color of terminal&quot;</userinput></para>
            </entry>
          </row>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--short-desc=<replaceable>description</replaceable></literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Use this option with the <literal>--set-schema</literal>
option to specify a short description for a schema key. </para>
            </entry>
          </row>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--shutdown</literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Terminates the <application>GConf</application> daemon.</para>
            </entry>
          </row>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--type=<replaceable>data_type</replaceable></literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Use this option to specify the data type when you set a
value of a preference key. You can also use this option when you set the value
of an attribute in a schema key. The following is a list of valid data types:</para>
              <itemizedlist>
                <listitem>
                  <para>
                    <literal>bool</literal>
                  </para>
                </listitem>
                <listitem>
                  <para>
                    <literal>float</literal>
                  </para>
                </listitem>
                <listitem>
                  <para>
                    <literal>int</literal>
                  </para>
                </listitem>
                <listitem>
                  <para>
                    <literal>list</literal>
                  </para>
                </listitem>
                <listitem>
                  <para>
                    <literal>pair</literal>
                  </para>
                </listitem>
                <listitem>
                  <para>
                    <literal>string</literal>
                  </para>
                </listitem>
              </itemizedlist>
            </entry>
          </row>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--unset</literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Resets the value of a preference
key from the user setting to the setting in the default configuration source.</para>
            </entry>
          </row>
          <row>
            <entry colname="colspec0" valign="top">
              <para>
                <literal>--usage</literal>
              </para>
            </entry>
            <entry colname="colspec1" valign="top">
              <para>Displays a brief help message
about the <command>gconftool-2</command> command, and the options that you
can use with the <command>gconftool-2</command> command.</para>
            </entry>
          </row>
        </tbody>
      </tgroup>
    </table>
  </sect1>
  <sect1 id="gconf-7">
    <title>To Set Preference Values</title>
    <indexterm>
      <primary>GConf</primary>
      <secondary>preference values, setting</secondary>
    </indexterm>
    <indexterm>
      <primary>preference values</primary>
      <secondary>setting
with GConf</secondary>
    </indexterm>
    <para>You can set a mandatory value or a
default value for a preference key. Before you change mandatory preference
values or default preference values for users, you must ensure that the <application>GConf</application> daemon is not running for any user. Ensure that all users
are logged out before you change preference values for users.</para>
    <para>To set a mandatory value or a default value for a preference key, use
the <command>gconftool-2</command> command, as follows:</para>
    <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source <replaceable>configuration_source</replaceable> --type <replaceable>data_type</replaceable>
--set <replaceable>preference_key</replaceable> <replaceable>value</replaceable></userinput></para>
    <para>For example, to set <literal>wwwproxy.xyz.com</literal> as the mandatory
HTTP proxy host, run the following command:</para>
    <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.mandatory --type string --set /system/http_proxy/host
wwwproxy.xyz.com</userinput></para>
    <para>The user cannot override this preference value.</para>
    <para>You can also use the <command>gconftool-2</command> command to set default
values. For example, to set the default number of workspaces to five, run
the following command:</para>
    <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.defaults --type int --set /apps/metacity/general/num_workspaces
5</userinput></para>
    <para>The user can override this preference value.</para>
    <caution>
      <para>Before you change mandatory preference values or default preference
values for users, you must ensure that all users are logged out.</para>
    </caution>
  </sect1>
  <sect1 id="gconf-8">
    <title>Setting General Preferences</title>
    <para>The following sections describe how to assign mandatory or default values
to general preferences.</para>
    <sect2 id="gconf-10">
      <title>To Set HTTP Proxy Preferences</title>
      <indexterm>
        <primary>GConf</primary>
        <secondary>HTTP proxy, setting</secondary>
      </indexterm>
      <indexterm>
        <primary>HTTP proxy</primary>
        <secondary>setting with
GConf</secondary>
      </indexterm>
      <para>To set HTTP proxy preferences, you modify
the values of the preference keys in the <filename>/system/http_proxy/</filename>
location. For example, to set a mandatory value for the HTTP proxy host, run
the following command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.mandatory --type string --set /system/http_proxy/host <replaceable>proxy_name</replaceable></userinput></para>
      <para>To set a default value for the HTTP proxy host, run the following command: </para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.defaults --type string --set /system/http_proxy/host <replaceable>proxy_name</replaceable></userinput></para>
      <para>You can also set other HTTP proxy-related preferences. For information
on the other HTTP proxy preferences, see the <filename>system_http_proxy.schemas</filename> schema definition file.</para>
    </sect2>
    <sect2 id="gconf-11">
      <title>To Set Print Manager Preferences</title>
      <para>To set print manager preferences, you modify the values of the preference
keys in the <filename>/apps/gnome-print-manager</filename> location. For example,
if you do not want users to view the print jobs of other users, set a mandatory
value as follows: </para>
      <indexterm>
        <primary>GConf</primary>
        <secondary>print manager, setting</secondary>
      </indexterm>
      <indexterm>
        <primary>print manager</primary>
        <secondary>setting
with GConf</secondary>
      </indexterm>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory
--type bool --set /apps/gnome-print-manager/show_all_jobs false</userinput></para>
      <para>To set a default value for this preference, run the following command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.defaults --type bool --set /apps/gnome-print-manager/show_all_jobs
false</userinput></para>
      <para>You can also set other print manager preferences. For information on
the other print manager preferences, see the <filename>gnome-print-manager.schemas</filename> schema definition file.</para>
    </sect2>
    <sect2 id="gconf-12">
      <title>To Set the Number of Workspaces</title>
      <indexterm>
        <primary>GConf</primary>
        <secondary>number of workspaces, setting</secondary>
      </indexterm>
      <indexterm>
        <primary>workspaces</primary>
        <secondary>setting number with GConf</secondary>
      </indexterm>
      <para>To set a mandatory
number of workspaces, use the following command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.mandatory --type int --set /apps/metacity/general/num_workspaces <replaceable>integer</replaceable></userinput></para>
      <para>To set a default number of workspaces, use the following command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.defaults --type int --set /apps/metacity/general/num_workspaces <replaceable>integer</replaceable></userinput></para>
      <para>You can also set other window manager preferences. For information on
the other window manager preferences, see the <filename>metacity.schemas</filename>
schema definition file.</para>
    </sect2>
    <sect2 id="gconf-16">
      <title>To Set Keyboard Accessibility Preferences</title>
      <indexterm>
        <primary>GConf</primary>
        <secondary>keyboard accessibility, setting</secondary>
      </indexterm>
      <indexterm>
        <primary>keyboard</primary>
        <secondary>setting accessibility preferences with GConf</secondary>
      </indexterm>
      <para>To set keyboard accessibility preferences, you modify the values of the preference
keys in the <filename>/desktop/gnome/accessibility/keyboard</filename> location.
For example, if you want to set a mandatory value so that keyboard accessibility
features are enabled, run the following command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.mandatory --type bool --set /desktop/gnome/accessibility/keyboard/enable
true</userinput></para>
      <para>To set a default value for this preference, run the following command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.defaults --type bool --set desktop/gnome/accessibility/keyboard/enable
false</userinput></para>
      <para>You can also set other keyboard accessibility preferences. For information
on the other keyboard accessibility preferences, see the <filename>desktop_gnome_accessibility_keyboard.schemas</filename> schema definition file.</para>
    </sect2>
    <sect2 id="gconf-18">
      <title>To Set Keyboard Shortcut Preferences</title>
      <indexterm>
        <primary>GConf</primary>
        <secondary>keyboard shortcuts, setting</secondary>
      </indexterm>
      <indexterm>
        <primary>keyboard</primary>
        <secondary>setting shortcut preferences with GConf</secondary>
      </indexterm>
      <para>To set
keyboard shortcut preferences, you modify the values of preference keys in
two locations. The following table shows the locations to modify, and the
part of the user interface to which the locations correspond:</para>
      <informaltable frame="topbot">
        <tgroup cols="2" colsep="0" rowsep="0">
          <colspec colwidth="50*"/>
          <colspec colwidth="50*"/>
          <thead>
            <row rowsep="1">
              <entry valign="top">
                <para>GConf Location</para>
              </entry>
              <entry valign="top">
                <para>User Interface Component</para>
              </entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry valign="top">
                <para>
                  <filename>/apps/panel/global</filename>
                </para>
              </entry>
              <entry valign="top">
                <para><application>Keyboard Shortcuts</application> preference
tool, <guilabel>Desktop</guilabel> section</para>
              </entry>
            </row>
            <row>
              <entry valign="top">
                <para>
                  <filename>/apps/metacity/general</filename>
                </para>
              </entry>
              <entry valign="top">
                <para><application>Keyboard Shortcuts</application> preference
tool, <guilabel>Window Management</guilabel> section</para>
              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>
      <para>For example, you might want users to use only the <keycombo><keycap>Alt</keycap><keycap>F3</keycap></keycombo>
 keyboard shortcut to open the <guilabel>Run Program</guilabel> dialog. To set this mandatory value, run the following command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.mandatory --type string --set /apps/panel/global/run_key
'&lt;Alt&gt;F3'</userinput></para>
      <para>You might want users to use <keycombo><keycap>Alt</keycap><keycap>F11</keycap></keycombo>
to maximize windows, by default. To set this default value, run the following
command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.defaults --type string --set /apps/metacity/window_keybindings/maximize
'&lt;Alt&gt;F11'</userinput></para>
      <para>You can also set other keyboard shortcut preferences. For information
on the other keyboard shortcut preferences, see the <filename>panel-global-config.schemas</filename> and <filename>metacity.schemas</filename> schema definition files.</para>
    </sect2>
    <sect2 id="gconf-13">
      <title>To Set Global Panel Preferences</title>
      <indexterm>
        <primary>GConf</primary>
        <secondary>global panel preferences, setting</secondary>
      </indexterm>
      <indexterm>
        <primary>panels</primary>
        <secondary>setting
global preferences with GConf</secondary>
      </indexterm>
      <para>To set global preferences
for panels, you modify the values of the preference keys in the <filename>/apps/panel/global</filename> location. For example, if you do not want users
to ever use panel animation, set a mandatory value as follows:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.mandatory --type bool --set /apps/panel/global/enable_animations
false</userinput></para>
      <para>To set a default value for this preference, run the following command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.defaults --type bool --set /apps/panel/global/enable_animations
false</userinput></para>
      <para>You can also set other global panel preferences. For information on
the other global panel preferences, see the <filename>panel-global-config.schemas</filename> schema definition file.</para>
    </sect2>
    <sect2 id="gconf-14">
      <title>To Set Preferences for Individual Panels and Panel Objects</title>
      <indexterm>
        <primary>GConf</primary>
        <secondary>panel object preferences, setting</secondary>
      </indexterm>
      <indexterm>
        <primary>GConf</primary>
        <secondary>panel
preferences, setting individual </secondary>
      </indexterm>
      <indexterm>
        <primary>panels</primary>
        <secondary>preferences, individual, setting with GConf</secondary>
      </indexterm>
      <para>The <filename>panel-per-panel-config.schemas</filename>
schema definition file specifies the following details of the panels on the
desktop:</para>
      <itemizedlist>
        <listitem>
          <para>Number of panels.</para>
        </listitem>
        <listitem>
          <para>Types of the panels.</para>
        </listitem>
        <listitem>
          <para>Properties of the panels.</para>
        </listitem>
        <listitem>
          <para>Contents of the panels.</para>
        </listitem>
      </itemizedlist>
      <para>The configuration of individual panels and of panel objects is a complex
task. To configure individual panels and panel objects, you must first understand
the structure of the <filename>panel-per-panel-config.schemas</filename> schema
definition file. For more information on the <filename>panel-per-panel-config.schemas</filename> schema definition file, see the next section.</para>
      <para>To set preferences for individual panels and panel objects, you must
set the values of many preferences in a configuration source. The easiest
way to set the values of many preferences is to use a script. For a sample
script that sets preferences for a panel and objects on the panel, see <xref linkend="gconf-3"/>.</para>
      <sect3 id="gconf-23">
        <title>Schema Definition File for Individual Panels and Panel Objects</title>
        <indexterm>
          <primary>GConf</primary>
          <secondary>schema definition files</secondary>
          <tertiary>panel and panel object</tertiary>
        </indexterm>
        <indexterm>
          <primary>schemas</primary>
          <secondary>schema definition files</secondary>
          <tertiary>panel and panel object</tertiary>
        </indexterm>
        <para>The schema definition file <filename>panel-per-panel-config.schemas</filename> contains sections that specify panels
and panel contents for small, medium, and large screens. The section for small
screens and the section for large screens are not functional at the time of
publication of this guide. To learn about preference keys for panels or panel
objects, read the section for medium screens only. </para>
        <para>The medium section of the file <filename>panel-per-panel-config.schemas</filename> is structured as follows:</para>
        <orderedlist>
          <listitem>
            <para>Preference keys that specify the general structure of panels,
applets, and other panel objects on the desktop. The following keys specify
the number of panels, applets, and other panel objects that appear on the
desktop:</para>
            <itemizedlist>
              <listitem>
                <para>
                  <literal>/apps/panel/default_profiles/medium/general/panel_id_list</literal>
                </para>
              </listitem>
              <listitem>
                <para>
                  <literal>/apps/panel/default_profiles/medium/general/applet_id_list</literal>
                </para>
              </listitem>
              <listitem>
                <para>
                  <literal>/apps/panel/default_profiles/medium/general/object_id_list</literal>
                </para>
              </listitem>
            </itemizedlist>
            <para>The keys also assign identifiers to each panel, applet, and panel object.
For example, the following excerpt from <filename>panel-per-panel-config.schemas</filename> specifies that two panels appear on the desktop:</para>
            <literallayout>&lt;key&gt;/schemas/apps/panel/default_profiles/medium/
general/panel_id_list&lt;/key&gt;
.
.
.
&lt;default&gt;[00000001,00000002]&lt;/default&gt;</literallayout>
            <para>In <filename>panel-per-panel-config.schemas</filename>, the identifier
00000001 identifies the bottom edge panel, and the identifier 00000002 identifies
the Menu Panel.</para>
          </listitem>
          <listitem>
            <para>Preference keys that specify the properties of the panels.
The panel property keys are structured as follows:</para>
            <literallayout>/apps/panel/default_profiles/medium/panels/<replaceable>panel_number</replaceable>/<replaceable>panel_property_key</replaceable></literallayout>
            <para>For example, the key <literal>/apps/panel/default_profiles/medium/panels/00000001/screen_edge</literal> specifies the edge of the display on which the bottom edge panel
resides. </para>
            <para>The keys that specify the properties of the bottom edge panel are listed
first. The keys that specify the properties of the Menu Panel are listed at
the end of the medium section in <filename>panel-per-panel-config.schemas</filename>. </para>
          </listitem>
          <listitem>
            <para>Preference keys that list the panel objects, the panel object
properties, and the panels in which the objects reside. For example, the following
excerpt from <filename>panel-per-panel-config.schemas</filename> specifies
object 00000001:</para>
            <literallayout>&lt;key&gt;/schemas/apps/panel/default_profiles/medium/
objects/00000001/object_type&lt;/key&gt;
.
.
.
&lt;default&gt;launcher-object&lt;/default&gt;
.
.
.
&lt;key&gt;/schemas/apps/panel/default_profiles/medium/
objects/00000001/launcher_location&lt;/key&gt;
.
.
.
&lt;default&gt;applications:///nautilus.desktop&lt;/default&gt;
.
.
.
&lt;key&gt;/schemas/apps/panel/default_profiles/medium/
objects/00000001/panel_id&lt;/key&gt;
.
.
.
&lt;default&gt;00000002&lt;/default&gt;</literallayout>
            <para>The object is a launcher that starts <application>Nautilus</application>
file manager. The launcher resides in the Menu Panel.</para>
          </listitem>
          <listitem>
            <para>Preference keys that list the applets, the applet preferences,
and the panels in which the applets reside. For example, the following excerpt
from <filename>panel-per-panel-config.schemas</filename> specifies applet
00000001:</para>
            <literallayout>&lt;key&gt;/schemas/apps/panel/default_profiles/medium/
applets/00000001/object_type&lt;/key&gt;
.
.
.
&lt;default&gt;bonobo-applet&lt;/default&gt;
.
.
.
&lt;key&gt;/schemas/apps/panel/default_profiles/medium/
applets/00000001/panel_id&lt;/key&gt;
.
.
.
&lt;default&gt;00000001&lt;/default&gt;
.
.
.
&lt;key&gt;/schemas/apps/panel/default_profiles/medium/
applets/00000001/bonobo_iid&lt;/key&gt;
.
.
.
&lt;default&gt;OAFIID:GNOME_TasklistApplet&lt;/default&gt;</literallayout>
            <para>The applet is the <application>Window List</application> applet. The
applet resides in the bottom edge panel.</para>
          </listitem>
        </orderedlist>
      </sect3>
      <sect3 id="gconf-3">
        <title>Sample Script for Setting Individual Panel Preferences</title>
        <para>This section contains a sample script that sets the preferences for
a panel that has the following major characteristics:</para>
        <itemizedlist>
          <listitem>
            <para>The panel is an edge panel, and resides at the bottom edge
of the screen.</para>
          </listitem>
          <listitem>
            <para>The panel contains a file manager launcher and a <application>Terminal</application> launcher.</para>
          </listitem>
          <listitem>
            <para>The panel contains a <application>Window List</application>
applet.</para>
          </listitem>
        </itemizedlist>
        <para>The sample script also sets other minor preferences. All of the preferences
have default values, not mandatory values.</para>
        <para>The sample script follows:</para>
        <literallayout># Usage is: set_key &lt;type&gt; &lt;key&gt; &lt;value&gt; &lt;extra options if any&gt;

function set_key() 
{
  TYPE=&quot;$1&quot;
  shift
  KEY=&quot;$1&quot;
  shift
  VALUE=&quot;$1&quot;
  shift
  OTHER_ARGS=&quot;$*&quot;
  gconftool-2 --direct --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults 
--owner=panel $OTHER_ARGS --type &quot;$TYPE&quot; --set &quot;$KEY&quot; &quot;$VALUE&quot;
}

# Define the number of panels, the number of launchers, and the number of applets 
set_key list /apps/panel/default_profiles/medium/general
/panel_id_list [00000001] --list-type string
set_key list /apps/panel/default_profiles/medium/general
/object_id_list [00000001,00000002] --list-type string
set_key list /apps/panel/default_profiles/medium/general
/applet_id_list [00000001] --list-type string

# Define the characteristics of the panel 
set_key string /apps/panel/default_profiles/medium/panels
/00000001/panel_type edge-panel
set_key string /apps/panel/default_profiles/medium/panels
/00000001/panel_size panel-size-x-small
set_key string /apps/panel/default_profiles/medium/panels
/00000001/screen_edge panel-edge-bottom
set_key bool /apps/panel/default_profiles/medium/panels
/00000001/hide_buttons_enabled false
set_key string /apps/panel/default_profiles/medium/panels
/00000001/panel_background_type no-background

# Define the first launcher
set_key string /apps/panel/default_profiles/medium/objects
/00000001/object_type launcher-object
set_key string /apps/panel/default_profiles/medium/objects
/00000001/launcher_location 'applications:///nautilus.desktop'
set_key string /apps/panel/default_profiles/medium/objects
/00000001/panel_id 00000001
set_key int /apps/panel/default_profiles/medium/objects
/00000001/position 20

# Define the second launcher
set_key string /apps/panel/default_profiles/medium/objects
/00000002/object_type launcher-object
set_key string /apps/panel/default_profiles/medium/objects
/00000002/launcher_location 'applications:///System/gnome-terminal.desktop'
set_key string /apps/panel/default_profiles/medium/objects
/00000002/panel_id 00000001
set_key int /apps/panel/default_profiles/medium/objects
/00000002/position 25

# Define the applet
set_key string /apps/panel/default_profiles/medium/applets
/00000001/object_type bonobo-applet
set_key string /apps/panel/default_profiles/medium/applets
/00000001/bonobo_iid OAFIID:GNOME_TasklistApplet
set_key string /apps/panel/default_profiles/medium/applets
/00000001/panel_id 00000001
set_key int /apps/panel/default_profiles/medium/applets
/00000001/position 25</literallayout>
      </sect3>
    </sect2>
  </sect1>
  <sect1 id="gconf-9">
    <title>Setting Look-and-Feel Preferences</title>
    <para>The following sections describe how to assign mandatory or default values
to look-and-feel preferences.</para>
    <sect2 id="gconf-19">
      <title>To Set Font Preferences</title>
      <indexterm>
        <primary>GConf</primary>
        <secondary>fonts, setting</secondary>
      </indexterm>
      <indexterm>
        <primary>fonts</primary>
        <secondary>setting with GConf</secondary>
      </indexterm>
      <para>To set font preferences, you modify the values of two preference
keys. The following table shows the keys to modify, and the part of the user
interface to which the keys correspond:</para>
      <informaltable frame="topbot">
        <tgroup cols="2" colsep="0" rowsep="0">
          <colspec colwidth="50*"/>
          <colspec colwidth="50*"/>
          <thead>
            <row rowsep="1">
              <entry valign="top">
                <para>GConf Location</para>
              </entry>
              <entry valign="top">
                <para>User Interface Component</para>
              </entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry valign="top">
                <para>/desktop/gnome/interface/font_name</para>
              </entry>
              <entry valign="top">
                <para><application>Font</application> preference tool, <guilabel>Application font</guilabel> section</para>
              </entry>
            </row>
            <row>
              <entry valign="top">
                <para>/apps/nautilus/preferences/desktop_font</para>
              </entry>
              <entry valign="top">
                <para><application>Font</application> preference tool, <guilabel>Desktop font</guilabel> section</para>
              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>
      <para>For example, to set <literal>Sans 12</literal> as the mandatory application
font, run the following command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.mandatory --type string --set /desktop/gnome/interface/font_name &ldquo;Sans
12&rdquo;</userinput></para>
      <indexterm>
        <primary>desktop background</primary>
        <secondary>font preferences,
setting with GConf</secondary>
      </indexterm>
      <para>To set <literal>palatino 12</literal> as the default desktop background object font, run the following
command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.defaults --type string --set /apps/nautilus/preferences/desktop_font &ldquo;palatino
12&rdquo;</userinput></para>
    </sect2>
    <sect2 id="gconf-20">
      <title>To Set Desktop Background Preferences</title>
      <indexterm>
        <primary>GConf</primary>
        <secondary>desktop background, setting</secondary>
      </indexterm>
      <indexterm>
        <primary>desktop background</primary>
        <secondary>preferences, setting with GConf</secondary>
      </indexterm>
      <para>To set desktop
background preferences, you modify the values of the preference keys in the <filename>/desktop/gnome/background</filename> location. For example, to set a mandatory
image for the desktop background, run the following command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.mandatory --type string --set /desktop/gnome/background/picture_filename <replaceable>filename.png</replaceable></userinput></para>
      <para>To set a default value for this preference, run the following command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.defaults --type string --set /desktop/gnome/background/picture_filename <replaceable>filename.png</replaceable></userinput></para>
      <para>You can also set other desktop background preferences. For information
on the other desktop background preferences, see the <filename>desktop_gnome_background.schemas</filename> schema definition file.</para>
    </sect2>
    <sect2 id="gconf-21">
      <title>To Set Splash Image Preferences</title>
      <indexterm>
        <primary>GConf</primary>
        <secondary>splash image, setting</secondary>
      </indexterm>
      <indexterm>
        <primary>splash screen</primary>
        <secondary>image, setting
with GConf</secondary>
      </indexterm>
      <para>To set splash image preferences, you
modify the value of the preference keys in the <filename>/apps/gnome-session/options/</filename> location. For example, if you do not want users ever to see a
splash image, set a mandatory value as follows:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.mandatory --type bool --set /apps/gnome-session/options/show_splash_screen
false</userinput></para>
      <para>To set a default value for this preference, run the following command:</para>
      <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source
xml:readwrite:/etc/gconf/gconf.xml.defaults --type bool --set /apps/gnome-session/options/show_splash_screen
false</userinput></para>
      <para>You can also set other splash image preferences. For information on
the other splash image preferences, see the <filename>gnome-session.schemas</filename> schema definition file.</para>
    </sect2>
  </sect1>
  <sect1 id="gconf-28">
    <title>To Restore Default Preference Values</title>
    <indexterm>
      <primary>GConf</primary>
      <secondary>restoring default preference
values</secondary>
    </indexterm>
    <indexterm>
      <primary>preference values</primary>
      <secondary>restoring to default with GConf</secondary>
    </indexterm>
    <para>To
restore the default preference values for a user, run the following command:</para>
    <para><computeroutput>#</computeroutput> <userinput>gconftool-2 --direct --config-source <replaceable>user_configuration_source</replaceable> --recursive-unset</userinput></para>
    <para>Replace <replaceable>user_configuration_source</replaceable> with the
configuration source in the <filename>.gconf</filename> directory in the home
directory of the user. </para>
    <para>This command resets the values of all preference keys, in all subdirectories,
from the user setting to the setting in the default configuration source.</para>
  </sect1>
</chapter>