# GNOME 桌面系统管理指南

The GNOME System Administration Guide provides information to administrators on how to configure and manage different aspects of the desktop environment for users.

2006
Brent Smith
2005
Brent Smith
2004
Sun Microsystems
2003
Sun Microsystems
GNOME 文档项目

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This manual is part of a collection of GNOME manuals distributed under the GFDL. If you want to distribute this manual separately from the collection, you can do so by adding a copy of the license to the manual, as described in section 6 of the license.

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Brent
Smith
GNOME 文档项目
Sun
GNOME 文档团队
Sun Microsystems
GNOME 2.14 桌面系统管理指南 V2.4
2004 年 3 月

GNOME 文档项目

GNOME 文档项目

GNOME 2.6 桌面系统管理指南 V2.3
2004 年 3 月

Sun Microsystems

GNOME 文档项目

GNOME 2.4 桌面系统管理指南 V2.2
2003 年 9 月

Sun Microsystems

GNOME 文档项目

GNOME 2.2 桌面系统管理指南 V2.1
2003 年 1 月

Sun Microsystems

GNOME 文档项目

GNOME 2.0 桌面系统管理指南 V2.0
2002 年 12 月

Sun Microsystems

GNOME 文档项目

This manual describes version 2.14 of the GNOME Desktop.

## 反馈

To report a bug or make a suggestion regarding the GNOME Desktop or this manual, follow the directions in the GNOME Feedback Page.

## 使用 GConf

The information in this chapter describes how to use GConf to manage user preferences.

### GConf 简介

GConf simplifies the administration of preferences for GNOME Desktop users. GConf enables system administrators to do the following:

- Set mandatory values for particular preferences for all users. In this way, system administrators can control whether users can update particular preferences.

- Set default values for particular preferences for all users.

- Use suggested values for preferences that are specified in definition files for the preferences.

- Read documentation on each preference.

GConf 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.

GConf has the following components:

- A repository of user preferences.

- A daemon, `gconfd-2`.

- A command line tool, `gconftool-2`.

### GConf Repository

Each preference in the GConf repository is expressed as a key-value pair. A GConf preference key is an element in the repository that corresponds to an application preference. For example, the /apps/gnome-session/options/show_splash_screen preference key corresponds to the Show splash screen on login option in the Sessions preference tool. The GNOME Desktop user interface does not contain all of the preference keys in the GConf repository. For example, the Panel preference tool does not contain an option that corresponds to the /apps/panel/global/tooltips_enabled key.

The repository is structured like a simple hierarchical file system. The repository contains the following:

- Directories that correspond to applications that use the GConf repository. For example, the file system contains the directory /apps/metacity.

- Subdirectories that correspond to categories of preferences. For example, the file system contains the directory /apps/metacity/general.

- 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 /system/http_proxy.

- A /schemas directory that contains files that describe all of the preference keys.

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 /desktop/gnome/interface/font_name preference key when an Extensible Markup Language (XML) backend module is used to read the repository:

    <entry name="font_name" mtime="1038323555" muser="user123" type="string">
    <stringvalue>Sans 10</stringvalue></entry>

When this guide refers to a preference key, the path to the key is added to the name of the key. For example, the font_name preference key in the /desktop/gnome/interface subdirectory is referred to as /desktop/gnome/interface/font_name.

#### GConf Configuration Sources

The GConf repository contains a series of storage locations that are called configuration sources. The configuration sources are listed in the GConf path file. The location of the GConf path file is /etc/gconf/gconf-version-number/path. Each user has a path file. The path file specifies the following information for each configuration source:

- The backend module to use to read the repository.

- The permissions on the repository.

- The location of the repository.

The GConf path file also contains include instructions. By default, the contents of the GConf path file are as follows:

    xml:readonly:/etc/gconf/gconf.xml.mandatory
    include /etc/gconf/2/local-mandatory.path
    include "$(HOME)/.gconf.path"
    include /etc/gconf/2/local-defaults.path
    xml:readwrite:$(HOME)/.gconf
    xml:readonly:/etc/gconf/gconf.xml.defaults

When GConf searches for a preference value, GConf reads the configuration sources in the order specified in the path file. The following table describes the configuration sources in the path file:

Configuration Source | Description
--- | ---
Mandatory | 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.
User | This configuration source is stored in the `.gconf` directory in the home directory of the user. When the user sets a preference, the new preference information is added to this location. You can use the Configuration Editor to modify the user configuration source.
Default | This configuration source contains the default preference settings.

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, GConf applies preferences in the following order of priority:

1. Mandatory preferences

2. User-specified preferences

3. Default preferences

The include instructions in the GConf path file enable system administrators to specify other configuration sources.

Included Configuration Source | Description
--- | ---
`/etc/gconf/2/local-mandatory.path` | Use this configuration source to store mandatory preference values for a particular system.
`$(HOME)/.gconf.path` | The user specifies the location of the configuration source in the home directory, in a file that is called `.gconf.path`.
`/etc/gconf/2/local-defaults.path` | Use this configuration source to store default preference values for a particular system.

#### GConf Schemas

A GConf schema is a collective term for a GConf schema key and a GConf schema object. The following table describes schema keys and schema objects and the relationship of these items to preference keys:

Item | Description
--- | ---
Preference key | An element in the GConf repository that corresponds to an application preference.
Schema key | A key that stores a schema object for a preference key.

Schema object

An element in a configuration source that contains information for a preference key, such as the following:

- The name of the application that uses the preference key.

- The type of value required for the preference key, for example integer, boolean, and so on.

- A default value for the preference key.

- Brief documentation on the preference key.

The following table gives examples of a preference key, a schema key, and a schema object:

Item | Example
--- | ---
Preference key | /desktop/gnome/interface/font_name
Schema key | /schemas/desktop/gnome/interface/font_name

Schema object

    <schema>
      <applyto>/desktop/gnome/interface/font_name</applyto>
      <key>/schemas/desktop/gnome/interface/font_name</key>
      <owner>gnome</owner>
      <type>string</type>
      <default>Sans 10</default>
      <locale name="C">
        <short>Default font</short>
          <long>Name of the default font used by gtk+.</long>
      </locale>
    </schema>

You can associate a schema key with a preference key. For example, the following /desktop/gnome/interface/font_name key includes a schema key:

    <entry name="font_name" mtime="1034873859"
    schema="/schemas/desktop/gnome/interface/font_name"/>

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 `<default>` element in the schema object. By default, all the preference keys in the default configuration source are associated with schema keys.

Typically, schemas are stored in the default configuration source.

#### GConf Schema Definition Files

Schemas are generated from schema definition files. A schema definition file defines the characteristics of all of the keys in a particular application. Schema definition files have a `.schemas` extension.

The schema definition files are included in the `/etc/gconf/schemas` directory. You can use the schema definition files to create a new configuration source.

Some schema definition files correspond closely to a part of the GNOME Desktop user interface. For example, `system_http_proxy.schemas` corresponds to the Network Proxy preference tool. Other schema definition files contain preference keys that are not present in the GNOME Desktop user interface. For example, the /apps/panel/global/tooltips_enabled key is not present in the user interface.

Some parts of the GNOME Desktop user interface contain preferences that represent preference keys from more than one schema definition file. For example, the Keyboard Shortcuts preference tool contains preferences that represent keys from the `panel-global-config.schemas` and `metacity.schemas` files.

### GConf Daemon

The GConf daemon is called `gconfd-2`. The GConf daemon notifies applications when a preference value changes. For example, you might select to show only icons in toolbars in the Menus & Toolbars preference tool. When you select this option in the preference tool, the toolbars on all open applications are updated instantly. The GConf daemon can operate locally, or across a network.

An instance of the GConf daemon is started for each user. The GConf daemon does not have to deal with complex problems such as authentication and data security. When the GConf daemon starts, the daemon loads the GConf path file. The GConf daemon manages all access between applications and the configuration sources.

When an application requests the value of a preference key, the daemon searches the configuration sources as follows:

1. 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.

2. 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.

3. If the schema key is found, check the value of the schema key.

4. If the value of the schema key is a schema object, return the suggested value in the `<default>` element of the schema object.

The GConf daemon also caches preference key values. All applications use this cache, so applications only need to access the configuration sources once.

To terminate the GConf daemon, run the following command:

    gconftool-2 --shutdown

### GConf Command Line Tool

GConf includes a command line tool, `gconftool-2`. You can use the `gconftool-2` command to perform the following tasks:

- Set the values of keys.

- Display the values of keys.

- Install schemas from schema definition files when you install an application.

For example, use the following command to display the values of all keys in the /desktop/gnome directory and subdirectories.

    gconftool-2 --recursive-list /desktop/gnome

Below are listed some of the options that you can use with the `gconftool-2` command. For detailed command line options, please see man:gconftool-2(1).

#### gconftool-2 Command Options

`--all-dirs`

  Lists all subdirectories in a directory that you specify.

`--all-entries`

  Displays the values of all keys in a directory that you specify.

`--config-source=configuration-source`

  Use this option with the `--direct` 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.

`--direct`

  Use this option with the `--config-source` option to access a configuration source directly. When you use this option, GConf bypasses the server. Ensure that the GConf daemon, `gconfd-2`, is not running before you use this option.

`--dump`

  Generates a list that contains all preference keys in a GConf repository directory that you specify. The list contains XML descriptions of all the keys. The list is contained in a `<gconfentryfile>` element.

  For example, you can redirect the output from this option to generate a file that lists all keys that are related to your panel configuration. You can use the `--load` option with this file.

`--get`

  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.

`--help`

  Displays a help message about the `gconftool-2` command, and the options that you can use with the `gconftool-2` command.

`--load=filename`

  Use this option to sets the values of preference keys in the current directory in a configuration source to the values in the file that you specify. The file that you specify must contain XML descriptions of the keys, in a `<gconfentryfile>` element.

`--long-desc=description`

  Use this option with the `--set-schema` option to specify a long description for a schema key.

`--makefile-install-rule`

  Installs schema definition files to applications.

`--owner=owner`

  Use this option with the `--set-schema` option to specify an owner for a schema key.

`--recursive-list`

  Displays the values of all preference keys in all subdirectories in a directory that you specify.

`--recursive-unset`

  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.

`--set`

  Sets the value of a preference key, and writes the value to the user configuration source. Use the `--type` option with the `--set` option to specify the data type of the value that you want to set. For example, the following command sets the value of the /apps/gnome-terminal/profiles/Default/background_color key in the user configuration source:

      gconftool-2 \
        --set "/apps/gnome-terminal/profiles/Default/background_color" \
        --type string "#000000"

  You can also use the `--direct` option and the `--config-source` option with the `--set` option to write a value to another configuration source.

`--set-schema`

  Sets the value of an attribute in a schema key, and writes the value to the default configuration source.

  Use the following options with the `--set-schema` option to specify the attribute that you want to update:

  - `--type`

  - `--short-desc`

  - `--long-desc`

  - `--owner`

  For example, the following command sets the short description in the schema key for the /apps/gnome-terminal/profiles/Default/background_color key:

      gconftool-2 \
        --set-schema  "/schemas/apps/gnome-terminal/profiles/Default/background_color" \
        --short-desc "Default  background color of terminal"

`--short-desc=description`

  Use this option with the `--set-schema` option to specify a short description for a schema key.

`--shutdown`

  Terminates the GConf daemon.

`--type=data-type`

  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:

  - bool

  - float

  - int

  - list

  - pair

  - string

`--unset`

  Resets the value of a preference key from the user setting to the setting in the default configuration source.

`--usage`

  Displays a brief help message about the `gconftool-2` command, and the options that you can use with the `gconftool-2` command.

### To Set Preference Values

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 GConf daemon is not running for any user. Ensure that all users are logged out before you change preference values for users.

To set a mandatory value or a default value for a preference key, use the `gconftool-2` command, as follows:

    gconftool-2 --direct \
      --config-source configuration-source \
      --type data-type \
      --set preference-key value

For example, to set `wwwproxy.xyz.com` as the mandatory HTTP proxy host, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type string \
      --set /system/http_proxy/host wwwproxy.xyz.com

The user cannot override this preference value.

You can also use the `gconftool-2` command to set default values. For example, to set the default number of workspaces to five, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults \
      --type int \
      --set /apps/metacity/general/num_workspaces 5

The user can override this preference value.

Before you change mandatory preference values or default preference values for users, you must ensure that all users are logged out.

### Setting General Preferences

The following sections describe how to assign mandatory or default values to general preferences.

#### To Set HTTP Proxy Preferences

To set HTTP proxy preferences, you modify the values of the preference keys in the /system/http_proxy/ location. For example, to set a mandatory value for the HTTP proxy host, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type string \
      --set /system/http_proxy/host proxy-name

To set a default value for the HTTP proxy host, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults \
      --type string \
      --set /system/http_proxy/host proxy-name

You can also set other HTTP proxy-related preferences. For information on the other HTTP proxy preferences, see the `system_http_proxy.schemas` schema definition file.

#### To Set Print Manager Preferences

To set print manager preferences, you modify the values of the preference keys in the /apps/gnome-print-manager location. For example, if you do not want users to view the print jobs of other users, set a mandatory value as follows:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type bool \
      --set /apps/gnome-print-manager/show_all_jobs false

To set a default value for this preference, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults \
      --type bool \
      --set /apps/gnome-print-manager/show_all_jobs false

You can also set other print manager preferences. For information on the other print manager preferences, see the `gnome-print-manager.schemas` schema definition file.

#### To Set the Number of Workspaces

To set a mandatory number of workspaces, use the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type int \
      --set /apps/metacity/general/num_workspaces integer

To set a default number of workspaces, use the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults \
      --type int \
      --set /apps/metacity/general/num_workspaces integer

You can also set other window manager preferences. For information on the other window manager preferences, see the `metacity.schemas` schema definition file.

#### To Set Keyboard Accessibility Preferences

To set keyboard accessibility preferences, you modify the values of the preference keys in the /desktop/gnome/accessibility/keyboard location. For example, if you want to set a mandatory value so that keyboard accessibility features are enabled, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type bool \
      --set /desktop/gnome/accessibility/keyboard/enable true

To set a default value for this preference, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults \
      --type bool \
      --set /desktop/gnome/accessibility/keyboard/enable false

You can also set other keyboard accessibility preferences. For information on the other keyboard accessibility preferences, see the `desktop_gnome_accessibility_keyboard.schemas` schema definition file.

#### To Set Keyboard Shortcut Preferences

To set keyboard shortcut preferences, you modify the values of preference keys in /apps/metacity/global_keybindings location. For example, you might want users to use only the AltF3 keyboard shortcut to open the Run Application dialog. To set this mandatory value, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type string \
      --set /apps/metacity/global_keybindings/panel_run_dialog '<Alt>F3'

You can also set other keyboard shortcut preferences. For information on the other keyboard shortcut preferences, see the `metacity.schemas` schema definition file.

#### Setting Panel and Panel Object Preferences

The `panel-default-setup.entries` file specifies the following details of the panels in the GNOME Desktop:

- Number of panels.

- Types of the panels.

- Properties of the panels.

- Contents of the panels.

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 `panel-default-setup.entries` file. For more information on the `panel-default-setup.entries` file, see the next section.

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 panel preferences is to use the `gconftool-2` command with the `--dump` and `--load` options. For more information on how to set preferences for panels and objects on panels, see .

##### Specifying Individual Panels and Panel Objects

The file `panel-default-setup.entries` contains sections that specify panels and panel contents. The `panel-default-setup.entries` file specifies values for schema keys. The `panel-default-setup.entries` file resides in the `/etc/gconf/schemas` directory.

The `panel-default-setup.entries` file is structured as follows:

1. Keys that specify the general structure of panels, applets, and other panel objects in the GNOME Desktop. The following keys specify the number of panels, panel objects, and applets that appear in the GNOME Desktop:

   - /apps/panel/default_setup/general/toplevel_id_list

   - /apps/panel/default_setup/general/object_id_list

   - /apps/panel/default_setup/general/applet_id_list

   The keys also assign identifiers to each panel, panel object, and applet. For example, the following sample from `panel-default-setup.entries` specifies that one panel appears in the GNOME Desktop:

       <entry>
         <key>toplevel_id_list</key>
         <schema_key>/schemas/apps/panel/general/toplevel_id_list</schema_key>
         <value>
           <list type="string">
             <value>
               <string>bottom_panel</string>
             </value>
           </list>
         </value>
       </entry>

   In the `panel-default-setup.entries` file, the identifier bottom_panel identifies the bottom edge panel.

2. Keys that specify the properties of the panels. The panel property keys are structured as follows:

       /apps/panel/default_setup/toplevels/panel-name/panel-property-key

   For example, the key /apps/panel/default_setup/toplevels/bottom_panel/size specifies the size of the bottom panel.

3. Keys that specify the panel objects, the panel object properties, and the panels in which the objects reside. For example, the following sample from `panel-default-setup.entries` specifies a Main Menu object at the left side of the bottom panel:

       <entrylist base="/apps/panel/default_setup/objects/main_menu">
         <entry>
           <key>object_type</key>
           <schema_key>/schemas/apps/panel/objects/object_type</schema_key>
           <value>
             <string>menu-object</string>
           </value>
         </entry>
         <entry>
           <key>toplevel_id</key>
           <schema_key>/schemas/apps/panel/objects/toplevel_id</schema_key>
           <value>
             <string>bottom_panel</string>
           </value>
         </entry>
         <entry>
           <key>position</key>
           <schema_key>/schemas/apps/panel/objects/position</schema_key>
           <value>
             <int>0</int>
           </value>
         </entry>
         <!-- Possibly more entry elements -->
       </entrylist>

4. Keys that specify the applets, the applet preferences, and the panels in which the applets reside. For example, the following sample from `panel-default-setup.entries` specifies the Window List applet, in the bottom panel:

       <entrylist base="/apps/panel/default_setup/applets/window_list">
         <entry>
           <key>object_type</key>
           <schema_key>/schemas/apps/panel/objects/object_type</schema_key>
           <value>
             <string>bonobo-applet</string>
           </value>
         </entry>
         <entry>
           <key>toplevel_id</key>
           <schema_key>/schemas/apps/panel/objects/toplevel_id</schema_key>
           <value>
             <string>bottom_panel</string>
           </value>
         </entry>
         <entry>
           <key>position</key>
           <schema_key>/schemas/apps/panel/objects/position</schema_key>
           <value>
             <int>2</int>
           </value>
         </entry>
         <!-- Possibly more entry elements -->
         <entry>
           <key>bonobo_iid</key>
           <schema_key>/schemas/apps/panel/objects/bonobo_iid_type</schema_key>
           <value>
             <string>OAFIID:GNOME_WindowListApplet</string>
           </value>
         </entry>
       </entrylist>

   The OAFIID is a unique identifier for an applet. To find the OAFIID for a particular applet, see the `.server` file for the applet in the `/usr/lib/bonobo/servers` directory. For example, the following excerpt from `GNOME_Wncklet_Factory.server` shows the OAFIID for the Window List applet:

       <oaf_server iid="OAFIID:GNOME_WindowListApplet"
       type="factory" location="OAFIID:GNOME_Wncklet_Factory">

##### To Set Preferences for Individual Panels and Panel Objects

To set the preferences for a panel and the objects on a panel perform the following steps:

1. Log in to a GNOME session, and configure the panels as required.

2. Use the `--dump` option with the `gconftool-2` command line tool to generate a file that contains an XML description of your panel configuration. The `--dump` option generates a list that contains all preference keys in a GConf repository directory that you specify.

   For example, the following command creates an XML description of the default panel configuration in a file called `my-panel-setup.entries`:

       gconftool-2 --dump /apps/panel > my-panel-setup.entries

3. Open the `my-panel-setup.entries` file in a text editor, and modify the file as required.

   For example, you might want to change the location of the desktop entry files. The following is an excerpt from a file generated with the `--dump` option:

       <entry>
         <key>objects/object_16/launcher_location</key>
         <schema_key>/schemas/apps/panel/objects/launcher_location</schema_key>
         <value>
           <string>hadjaha-00adce02f7.desktop</string>
         </value>
       </entry>

   In the sample above, you might want to change the reference to `hadjaha-00adce02f7.desktop` to another desktop entry file that is available globally.

   When you generate a panel configuration with the `--dump` option, the positions of the panel objects are absolute positions. You might want to change the positions of panel objects from absolute positions to relative positions. The object at the extreme left of a panel has a position value of `0`. The next object has a position value of `1`, and so on. If you want object positions to be relative to the right side of the panel, set the value of the right_stick key to `true`.

4. Use the `--load` option with the `gconftool-2` command line tool to set the values of the default configuration source to the values in the `my-panel-setup.entries` file. For example, the following command sets the values of the keys in the default configuration source to the values of the corresponding keys in `my-panel-setup.entries`:

       gconftool-2 --direct \
         --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults \
         --load my-panel-setup.entries

### Setting Look-and-Feel Preferences

The following sections describe how to assign mandatory or default values to look-and-feel preferences.

#### To Set Font Preferences

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:

GConf Location | User Interface Component
--- | ---
/desktop/gnome/interface/font_name | Font preference tool, Application font option
/apps/nautilus/preferences/desktop_font | Font preference tool, Desktop font option

For example, to set `Sans 12` as the mandatory application font, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type string \
      --set /desktop/gnome/interface/font_name "Sans 12"

To set `palatino 12` as the default desktop object font, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults \
      --type string \
      --set /apps/nautilus/preferences/desktop_font "palatino 12"

#### To Set Background Preferences

To set preferences for the desktop background, you modify the values of the preference keys in the /desktop/gnome/background location. For example, to set a mandatory image for the background, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type string \
      --set /desktop/gnome/background/picture_filename filename.png

To set a default value for this preference, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults \
      --type string \
      --set /desktop/gnome/background/picture_filename filename.png

You can also set other background preferences. For information on the other background preferences, see the `desktop_gnome_background.schemas` schema definition file.

#### To Set Splash Image Preferences

To set splash image preferences, you modify the value of the preference keys in the /apps/gnome-session/options/ location. For example, if you do not want users ever to see a splash image, set a mandatory value as follows:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type bool \
      --set /apps/gnome-session/options/show_splash_screen false

To set a default value for this preference, run the following command:

    gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults \
      --type bool \
      --set /apps/gnome-session/options/show_splash_screen false

You can also set other splash image preferences. For information on the other splash image preferences, see the `gnome-session.schemas` schema definition file.

### To Restore Default Preference Values

To restore the default preference values for a user, run the following command:

    gconftool-2 --direct \
      --config-source user-configuration-source \
      --recursive-unset

Replace user-configuration-source with the configuration source in the `.gconf` directory in the home directory of the user.

This command resets the values of all preference keys, in all subdirectories, from the user setting to the setting in the default configuration source.

## Customizing Menus

The information in this chapter describes how the GNOME Desktop implements menus and how you can customize menus.

### Introduction to Menus

The GNOME Desktop implements menus according to the XDG menu specification. By supporting this specification, GNOME allows you to:

- Customize the menu hierarchy easily. You can edit a small number of files to customize the menu hierarchy. You do not need to modify your applications or move files.

- Install applications easily. You do not need to provide information about the menu hierarchy to applications when you install the applications.

- Configure menus so that users cannot modify the menus.

Menus in the GNOME Desktop use the following components:

- Menu definition files

- Desktop entry files

- Directory entry files

### Menu Definition Files

Menu files define the hierarchy of menus that are used in the GNOME menu bar. By modifying these files, you can customize menus for all users, or for a single user depending on the location of the `applications.menu` file that you modify.

Menu files must reside at `$XDG_CONFIG_DIRS/menus/applications.menu`. If `$XDG_CONFIG_DIRS` $XDG_CONFIG_DIRS is the environment variable defined in the XDG base directory specification. is not set, then the default path `/etc/xdg` is used. This also implies that a user specific version may be located at `$XDG_CONFIG_HOME/menus/applications.menu` which is searched first. If `$XDG_CONFIG_HOME` is not set, then the default path `~/.config` is used. Directories which appear first in `$XDG_CONFIG_DIRS` are given precedence when there are several `applications.menu` files. The first file found is used and subsequent files are ignored.

If you are confused about the order in which paths are searched, here is a simple list for resolving the location of `applications.menu`:

1. Search each directory in `$XDG_CONFIG_HOME` in order to find `menus/applications.menu`. If `$XDG_CONFIG_HOME` is not set, it defaults to the `~/.config/` directory.

2. Search each directory in `$XDG_CONFIG_DIRS` in order to find `menus/applications.menu`. If `$XDG_CONFIG_DIRS` is not set, it defaults to the `/etc/xdg/` directory.

3. Use the first `applications.menu` file found.

You can see an example of a `.menu` file in . In this example, the top level menu is named `Applications`, which is specified using the `<Name>` element. The `Applications` menu contains a single submenu, but several submenus are allowed. Each submenu may also have an `<Include>` element. The purpose of the `<Include>` element is to perform a filter on the set of available desktop entries using matching rules.

For example, the `<Category>` element is a basic matching rule that selects a desktop entry only if the `Categories` key contains the content of the `<Category>` element. In the example, the `Accessories` menu will include a desktop entry only if it contains Utility but not System in the Categories key. For more information on the Categories key, see .

#### Example of a `.menu` file

    <!DOCTYPE Menu PUBLIC "-//freedesktop//DTD Menu 1.0//EN"
     "http://www.freedesktop.org/standards/menu-spec/1.0/menu.dtd">
    <Menu>
      <Name>Applications</Name>
      <Directory>Applications.directory</Directory>

      <!-- Read standard .directory and .desktop file locations -->
      <DefaultAppDirs/>
      <DefaultDirectoryDirs/>

      <!-- Accessories submenu -->
      <Menu>
        <Name>Accessories</Name>
        <Directory>Accessories.directory</Directory>
        <Include>
          <And>
            <Category>Utility</Category>
            <Not>
              <Category>System</Category>
            </Not>
          </And>
        </Include>
      </Menu> <!-- End Accessories -->

      <!-- possibly more submenus -->

    </Menu> <!-- End Applications -->

describes some of the elements in `.menu` files. For a more detailed description, please see the XDG menu specification.

#### Menu Definition File Elements

Element | Description
--- | ---
`<Menu>` | The root element which may contain nested `<Menu>` elements that define submenus. How these elements are nested determines the menu structure.
`<Name>` | Specifies the name of the menu. Every `<Menu>` element must contain a `<Name>` element.
`<Directory>` | Specifies the name of the directory entry file that specifies the name, comment, and icon for the menu. If this element is not specified, then the `<Name>` element is to be used to display the menu name. By default, `.directory` files are searched for in the location `$XDG_DATA_DIRS/desktop-directories/` as set forth in the XDG menu specification.
`<DefaultAppDirs>` | This is an instruction which indicates that all the available desktop entries from `$XDG_DATA_DIRS/applications/` should be scanned. If this instruction is not included, then these locations are not scanned for desktop entries.
`<DefaultDirectoryDirs>` | This is an instruction which indicates that all the available directory entries from `$XDG_DATA_DIRS/desktop-directories/` should be scanned. If the instruction is not included, then these locations are not scanned for directory entries.
`<Include>` | Contains a list of matching rules by which the contents of a menu are generated. May include the `<Filename>`, `<Category>`, `<And>`, `<Or>`, `<Not>`, or `<All>` matching rules. If more than one rule is present, the rules are logically ORed so that desktop entries that match any rule are included.
`<Exclude>` | The opposite of `<Include>` since any desktop entries that are matched in this element are excluded from the previous set of included elements. For this reason, this element must appear after the `<Include>` element.
`<Filename>` | A matching rule that selects a desktop entry when the Desktop File-Id matches the contents of the `<Filename>` element.
`<Category>` | A matching rule that selects a desktop entry when the Categories key matches the contents of the `<Category>` element.
`<And>` | A matching rule that selects a desktop entry when it is selected by all the nested matching rules in the `<And>` element.
`<Or>` | A matching rule that selects a desktop entry when it is selected by any of the nested matching rules in the `<Or>` element.
`<Not>` | A matching rule that does not select a desktop entry when it is selected by any of the nested matching rules in the `<Not>` element.
`<All>` | A matching rule which selects all desktop entries.

### Desktop Entry Files

A desktop entry file is a data file that provides information about an item in a menu. The desktop entry file specifies the details for the item such as a name, a command to run, an icon, and so on. It also contains keywords which determine the location of the item in the menu hierarchy.

Desktop entry files must reside in the `$XDG_DATA_DIRS/applications` directory and must have a `.desktop` file extension. If `$XDG_DATA_DIRS` $XDG_DATA_DIRS is the environment variable defined in the XDG base directory specification. is not set, then the default path is `/usr/share` is used. This also implies that user specific desktop entries may be located at `$XDG_DATA_HOME/applications` which is searched first. If `$XDG_DATA_HOME` is not set, then the default path `~/.local/share` is used. Desktop entries are collected from all directories in the `$XDG_DATA_DIRS` environment variable. Directories which appear first in `$XDG_DATA_DIRS` are given precedence when there are several `.desktop` files with the same name.

The following is a sample desktop entry file:

    [Desktop Entry]
    Encoding=UTF-8
    Name=Calculator
    Name[fr]=Calculatrice
    ...
    Comment=Perform calculations
    Comment[fr]=Effectue des calculs compliqués
    ...
    Exec=gcalctool
    Icon=accessories-calculator
    Terminal=false
    Type=Application
    StartupNotify=true
    Categories=GNOME;GTK;Utility;Calculator

describes the most important keys in desktop entry files. To get more information about desktop entry files, see the XDG Desktop Entry Specification.

#### Desktop Entry Keys

Desktop Entry Key | Description
--- | ---
`Categories` | Specifies the keywords that describe the item. The keywords are separated with semicolons (;). To see a list of the standard category keywords, see the desktop menu specification at http://www.freedesktop.org/Standards/menu-spec Menu Definition Files map desktop entries to menus by using matching rules against the Categories key.
`Comment` | Specifies a short description of the item. The comment is displayed as a tooltip when you point to the item in the menu.
`Encoding` | Specifies the encoding of the desktop entry file.
`Exec` | Specifies a command to execute when you choose the item from the menu.
`Icon` | Specifies the filename of an icon that represents the item. Does not specify the path to the filename, or the file extension.
`MimeType` | Specifies the MIME types that the application can handle.
`Name` | Specifies the name of the item. This name is displayed on the item in the menu.
`NoDisplay` | This options means This application exists, but don't display it in the menus.
`Terminal` | Specifies whether the command in the `Exec` key runs in a terminal window. If the value is `true` the command runs in a terminal window. If the command does not create a window in which to run, the value of this key must be `true`.

`Type`

Specifies the type of item. This value is one of the following:

- `Application`: An item that starts an application.

- `Link`: An item that links to a file, folder, or a remote resource (such as a FTP site, a web page, a Windows share...).

- `FSDevice`: An item that is a file system device.

- `Directory`: An item that is a Directory.

For more information on the keys in desktop entry files, see the desktop entry specification at the following URL:

        http://www.freedesktop.org/Standards/desktop-entry-spec

Panel launchers and desktop objects also use desktop entry files. The desktop entry files for launchers and desktop objects provide the same information as for items in a menu. For example, the desktop entry files provide the command to run when a user chooses the launcher or object.

### Directory Entry Files

A directory entry file is a data file that provides information about a menu. The directory entry file specifies the details for the menu such as a name, a tooltip, and an icon. Directory entry files have a `.directory` file extension.

Directory entry files must reside in the `$XDG_DATA_DIRS/desktop-directories` directory. If `$XDG_DATA_DIRS` is not set, then the default path is `/usr/share` is used. This also implies that user specific directory entries may be located at `$XDG_DATA_HOME/desktop-directories` which is searched first. If `$XDG_DATA_HOME` is not set, then the default path `~/.local/share` is used. Directory entries are collected from all directories in the `$XDG_DATA_DIRS` environment variable. Directories which appear first in `$XDG_DATA_DIRS` are given precedence when there are several `.directory` files with the same name.

The following is a sample directory entry file:

    [Desktop Entry]
    Name=Graphics
    Name[fr]=Graphisme
    ...
    Comment=Graphics applications
    Comment[fr]=Applications graphiques
    ...
    Icon=gnome-graphics
    Type=Directory
    Encoding=UTF-8

describes the most important keys in directory entry files.

#### Directory Entry Keys

Directory Entry Key | Description
--- | ---
`Name` | Specifies the name of the menu. This name is displayed on the menu.
`Comment` | Specifies a short description of the menu. The comment is displayed as a tooltip when you point to the menu.
`Icon` | Specifies the filename of an icon that represents the menu. Does not specify the path to the filename, or the file extension.
`Type` | Specifies the type of menu. The value of this key is always `Directory`.

### Editing System Menus

You can edit menu configuration files and menu data files manually to customize menus.

#### Adding Menus

To add a menu for all users, perform the following steps:

1. Create a directory entry file for the item that you want to add. Place the directory entry file in the `$XDG_DATA_DIRS/desktop-directories` directory. For more information on directory entry files, see .

2. Locate the `$XDG_CONFIG_DIRS/menus/applications.menu` file.

3. In the `.menu` file, add a `<Menu>` element for the new menu. For more information on `.menu` files, see .

4. Create a `<Name>` element below `<Menu>`. The content of the element should contain the name for the menu.

5. Create a `<Directory>` element below `<Menu>`. The content of the element should contain the name of the directory entry file.

6. See for how to add an item to the menu.

The next time that users log in, the menu should appear in the menu bar.

##### Missing Menu?

If you did not specify any matching rules in the `<Include>` element, or if the rule did not match any desktop entries, then you may not see the menu in the menu bar.

#### Adding an Item to a Menu

To add an item to a menu for all users, perform the following steps:

1. Create a desktop entry file for the item that you want to add. For more information on desktop entry files, see .

2. Place the desktop entry file in the `$XDG_DATA_DIRS/applications` folder.

3. Locate the `$XDG_CONFIG_DIRS/menus/applications.menu` file.

4. Verify that a `<Menu>` element contains an `<Include>` element with a matching rule that selects the desktop entry file made in step 1.

The next time that users log in, the menu item is in the assigned location.

#### Editing the Properties of a Menu

To edit the properties of a menu for all users, perform the following steps:

1. Locate the `$XDG_CONFIG_DIRS/menus/applications.menu` file.

2. Find the `<Menu>` entry in this file that corresponds to the menu you want to modify. Note the filename of the directory entry in the `<Directory>` element.

3. Locate the directory entry for this menu. Modify the contents to change the properties of the menu. For more information on `.directory` files, see .

#### Editing a Menu Item

To edit a menu item, perform the following steps:

1. Locate the desktop entry in the `$XDG_DATA_DIRS/applications` directory that corresponds to the menu item.

2. Edit the desktop entry to change the properties of the menu item. For more information on desktop entry files, see .

#### Deleting an Item from a Menu

To delete an item from a menu for all users:

1. Locate the `$XDG_CONFIG_DIRS/menus/applications.menu` file.

2. Find the `<Menu>` element in this file that contains the desktop entry you want to delete.

3. Insert an `<Exclude>` element after the closing tag for the `<Include>` element. Make sure this is in the `<Menu>` element determined in step 2.

4. Insert the `<Filename>` matching rule as a subelement of `<Exclude>` to specifically exclude a desktop entry.

The next time that users log in, the menu item is not displayed in the menu. shows how this done in the `applications.menu` file. The desktop entry for `dasher.desktop` is explicitly excluded from showing up in the accessibility menu.

##### Deleting an Item from a Menu

    <!-- ... -->

      <Menu>
        <Name>Accessibility</Name>
        <Directory>Accessibility.directory</Directory>
        <Include>
          <And>
            <Category>Accessibility</Category>
            <Not><Category>Settings</Category></Not>
          </And>
        </Include>
        <Exclude>
          <Filename>dasher.desktop</Filename>
        </Exclude>
      </Menu>

    <!-- ... -->

### Editing User Menus and Menu Merging

You can use the following GNOME Desktop applications to edit menus for users:

- GNOME Menu Editor

A simple menu editor is available for users to edit their menus. For more information, see Working With Menus in the GNOME User Guide. Alternatively, you can manually create and edit a user menu file.

To manually create a custom menu for a user, the `$XDG_CONFIG_HOME/menus/applications.menu` must exist. In the case that `$XDG_CONFIG_HOME` is not set, the default `~/.config` directory is used. Since this is the first location that is searched for the `applications.menu` file, it takes precedence over all other menu files.

User menus can contain all the elements described in . For a complete list of the elements allowed, see the XDG menu specification.

Since user menu files take precedence over the system menu file, it will completely replace the system menu unless it explicitly merges the system menu. Information on menu merging is available in the following subsections.

#### Merging the System Menu

Often, a user only wants to add or delete menu items in addition to the standard system menu. To support single changes like these, it is recommended that you use the `<MergeFile>` element with the attribute `type="parent"` within the user's `applications.menu` file.

The `<MergeFile>` element allows a menu to be merged with the contents of the user's menu file. When you specify the attribute `type="parent"`, then the contents of the `<MergeFile>` element are ignored and the next `applications.menu` file in the `$XDG_CONFIG_DIRS/menus` directory is used for merging.

##### Older Specifications

Older specifications did not include the `type` attribute and simply required the location of the menu file to be merged as the content of the `<MergeFile>` element. As a result, you may still see a location specified in the contents of `<MergeFile>`, even when `type="parent"`.

The merging is performed as follows:

- The children of the root `<Menu>` element in the merged menu file Merged menu file refers to the next `applications.menu` in the `$XDG_CONFIG_DIRS/menus` directory. are substituted for the `<MergeFile>` element in the base menu file.

- All child `<Menu>` elements with the same name are consolidated into a single `<Menu>` element. This is by done appending all child elements of each `<Menu>` element with the same name into the last occurrence of the menu element.

shows an example of a user menu file explicitly merging the system menu file.

##### Merging the System Menu

    <!DOCTYPE Menu PUBLIC "-//freedesktop//DTD Menu 1.0//EN"
     "http://www.freedesktop.org/standards/menu-spec/menu-1.0.dtd">

    <Menu>
      <Name>Applications</Name>
      <MergeFile type="parent">/etc/xdg/menus/applications.menu</MergeFile>
      <Menu>
        <Name>Accessibility</Name>
        <Exclude>
          <Filename>dasher.desktop</Filename>
        </Exclude>
      </Menu>
    </Menu>

#### Merging Arbitrary Menus

Arbitrary menu files can be merged in much the same way as system menus. The difference is that the `type` attribute must be set to `path` or must be excluded from the `<MergeFile>` element in order to do this type of merge.

The merge is performed in the same way except that the location of the merged menu file is specified in the contents of the `<MergeFile>` element.

## Installing Themes

This chapter describes themes, the theme settings that are available in the GNOME Desktop, how to install options for theme settings, and how to create a custom option.

### Introduction to Themes

A theme is a group of coordinated settings that specifies the visual appearance of a part of the GNOME Desktop. Users can choose themes to change the appearance of the GNOME Desktop.

A theme contains settings that affect different parts of the GNOME Desktop, as follows:

Controls

  The controls setting for a theme determines the visual appearance of windows, panels, and applets. The controls setting also determines the visual appearance of the GNOME-compliant interface items that appear on windows, panels, and applets, such as menus, icons, and buttons. Some of the controls setting options that are available are designed for special accessibility needs. Users can choose an option for the controls setting from the Controls tabbed section in the Theme preference tool.

Window frame

  The window frame setting for a theme determines the appearance of the frames around windows only. Users can choose an option for the window frame setting from the Window Border tabbed section in the Theme preference tool.

Icon

  The icon setting for a theme determines the appearance of the icons on panels and the desktop background. Users can choose an option for the icon setting from the Icons tabbed section in the Theme preference tool.

### Theme Index File

Each theme has an index file which defines the characteristics of the theme. The name of the index file is `/usr/share/themes/theme-name/index.theme`.

The following is a sample theme index file:

    [Desktop Entry]
    Type=X-GNOME-Metatheme
    Name=High Contrast Large
    Name[es]=Alto contraste grande
    Comment=Large black-on-white text and icons
    Comment[es]=Textos e iconos grandes en negro sobre blanco
    Encoding=UTF-8

    [X-GNOME-Metatheme]
    GtkTheme=HighContrastLargePrint
    IconTheme=HighContrast
    MetacityTheme=Atlanta
    ApplicationFont=sans 18

The following table describes the keys in theme index files:

#### Keys in Theme Index Files

Index File Key | Description
--- | ---
`Type` | Specifies that this theme determines the appearance of several theme options, such as controls, window frames, and icons.
`Name` | The name of the theme. This is the name of the theme that is displayed in the Theme preference tool.
`Comment` | A brief description of the theme. This is the text that is displayed under the name of the theme in the Theme preference tool.
`GtkTheme` | Corresponds to the controls setting in the Theme preference tool. Specifies which controls setting option to apply to windows, panels, and applets.
`IconTheme` | Corresponds to the icons setting in the Theme preference tool. Specifies which icons setting option to apply to panels and the desktop background.
`MetacityTheme` | Corresponds to the window frame setting in the Theme preference tool. Specifies which window frame setting option to apply to windows.
`ApplicationFont` | Corresponds to the application font setting in the Font preference tool.

### To Install a New Controls Option

You can add a new option for the controls setting in the Theme preference tool. Controls options reside in the `/usr/share/themes` directory. The typical structure of a controls option in the file system is as follows:

Option file

  `/usr/share/themes/option-name/gtk-2.0/gtkrc`

Image files

  `/usr/share/themes/option-name/pixmaps/*.*`

Typically, a new option for the controls setting is supplied as a `.tar.gz` file. To install the new controls option, unzip the `.tar.gz` file, then untar the `.tar` file into the `/usr/share/themes` directory.

Users can install their own options for the controls setting. If a user installs an option for the controls setting, the option is stored in the `$HOME/.themes` directory.

### To Install a New Window Frame Option

You can add a new option for the window frame setting in the Theme preference tool. Window frame options reside in the `/usr/share/themes/option-name/metacity-1` directory. The typical structure of a window frame option in the file system is as follows:

Option file

  `/usr/share/themes/option-name/metacity-1/metacity-theme-1.xml`

Image files

  `/usr/share/themes/option-name/metacity-1/*.*`

Typically, a new option for the window frame setting is supplied as a `.tar.gz` file. To install the new window frame option, unzip the `.tar.gz` file, then untar the `.tar` file into the `/usr/share/themes` directory.

Users can install their own options for the window frame setting. If a user installs an option for the window frame setting, the option is stored in the `$HOME/.themes` directory.

### To Install a New Icons Option

You can add a new option for the icons setting in the Theme preference tool. Icons options reside in the `/usr/share/icons/option-name` directory. The typical structure of an icons option in the file system is as follows:

Option file

  `/usr/share/icons/option-name`

Image files

  `/usr/share/icons/option-name/icons/*.*`

Typically, a new option for the icons setting is supplied as a `.tar.gz` file. To install the new icons option, unzip the `.tar.gz` file, then untar the `.tar` file into the `/usr/share/icons` directory.

Users can install their own options for the icons setting. If a user installs an option for the icons setting, the option is stored in the `$HOME/.icons/option-name` directory.

### Installing Icons for Themes

The GNOME Desktop provides several themes that are designed for users with special visual needs. For example, some of the themes are designed for users with low vision. Several versions of icons might be required so that the icon can be displayed properly in each theme.

You might need to install a new icon for an application. When you install a new icon, you must create several versions of the icon, so that the icon displays correctly in the themes. You must create several versions of the following types of icon:

- Icons that are used within applications in the GNOME Desktop.

- Icons that are used internally by GTK+ applications, or GTK+ stock icons.

When you install a new icon, you must create several versions of the icon, so that the icon displays correctly in the themes. You can create the icons in several formats, for example Portable Network Graphic (PNG) format. The suggested size of icons for the desktop environment is 48 pixels by 48 pixels. At this size, most themes can rescale the icons.

When you install a new icon, create the following 48 pixel by 48 pixel versions of the icon:

- Regular icon

- Low contrast icon

- High contrast icon

- Inverse high contrast icon

If possible, create 16 pixel by 16 pixel versions of the each of the icons above also, for themes that do not require large print.

Install the icons to the image files location that is specified for the theme in or . For example, to add icons to the HighContrastLargePrint theme, add the icons to the `/usr/share/themes/HighContrastLargePrint/pixmaps` directory. Add references to the icons to the relevant theme files. For example, to add icons to the HighContrastLargePrint theme, add references to the icons to the `/usr/share/themes/HighContrastLargePrint/gtk-2.0/gtkrc` file. Modify the `gtkrc` file for the theme to associate the icon with a GTK stock icon identifier.

For more information on how to create icons for application launchers and for panels, see http://www.freedesktop.org/Standards/icon-theme-spec.

### To Create a Custom Controls Option

If the options for the controls setting are not suitable for the needs of your users, you can create a custom controls option. To create a custom controls option, perform the following steps:

1. Create a directory structure for the option in the `/usr/share/themes` directory. Use the same directory structure that other options use. For example, to create an option that is called SmallPrint, create the following directories:

   - `/usr/share/themes/SmallPrint`

   - `/usr/share/themes/SmallPrint/gtk-2.0`

2. Locate the `gtkrc` file that is closest to meeting the needs of your users. Copy the file to the `gtk-2.0` directory of your new option.

3. Open the `gtkrc` file in a text editor, and modify the attributes of the interface elements as required.

4. If the new option includes images, install the images for the new option in the `pixmaps` directory of your new option. If the new option uses images from another option, you do not need to create copies of the images for the new option. Instead, ensure that the reference to the images in the `pixmap_path` entry in the `gtkrc` file is correct.

Users can now choose the new option for the controls setting.

For more information on `gtkrc` files, see http://developer.gnome.org/doc/API/2.0/gtk/index.html.

## Configuring Fonts

This chapter describes how to configure fonts in the GNOME Desktop.

### Introduction to Configuring Fonts

GNOME Desktop uses the `fontconfig` font configuration and customization library. The `fontconfig` library can use all kinds of fonts, including PostScript Type 1 fonts and TrueType fonts.

The `fontconfig` library provides a list of all the fonts available on a GNOME Desktop system. To compile this list, `fontconfig` searches the directories listed in the `/etc/fonts/fonts.conf` file. To view all the fonts available on a system, access the `fonts:///` location in the file manager on the system.

For more information about the `fontconfig` library, see the following URL:

          http://freedesktop.org/software/fontconfig

### Font Substitution

The `fontconfig` library performs font substitution when either entire fonts, or individual characters, are not present. If the system needs to display a font that is not available, `fontconfig` attempts to display another, similar font. For example, if a web page requests to display the Verdana font, and that font is not installed on the system, `fontconfig` displays a similar font, such as Helvetica. The list of similar fonts is defined in the `/etc/fonts/fonts.conf` file.

If the system needs to display a character that is not present in the selected font, `fontconfig` attempts to display the character in another, similar font. For example, you might select Bitstream Vera Sans as the font for the Text Editor application. The Bitstream Vera font family does not include Cyrillic characters. If you open a document which contains a Cyrillic character, Text Editor uses a similar font that includes Cyrillic characters to display the character.

The `fontconfig` library also defines aliases for fonts, for example, `serif`, `sans-serif`, and `monospace`. When you select one of the aliases for a font, the system uses the first font that is defined for that alias in the `/etc/fonts/fonts.conf`.

### To Add a Font for All Users

To add a font for all users, perform the following steps:

1. Copy the font file to one of the directories in the `/etc/fonts/fonts.conf` file. Typically, fonts are stored in the `/usr/share/fonts/` directory.

2. The `fontconfig` library updates the list of fonts automatically. If the list of fonts is not updated, run the following command:

       fc-cache directory-name

### To Add a Font for an Individual User

To add a font for an individual users, perform the following steps:

1. Copy the font file to the `$HOME/.fonts` directory of the user. If you drag the font file to the `fonts:///` location in the file manager, the font file is copied to the `$HOME/.fonts` directory.

2. The `fontconfig` library updates the list of fonts automatically. If the list of fonts is not updated, run the following command:

       fc-cache directory-name

## MIME Types

This chapter describes how applications detect MIME types, how to register MIME types, and how to add applications to the GNOME Desktop.

The purpose of this chapter is to make it easy for an administrator to understand how to configure different parts of the MIME database and give an general overview of the MIME system. Therefore we will not attempt to go into details where it is not necessary. For the gory details, it is recommended that you refer to the XDG shared mime info specification.

### Introduction to MIME Types

A Multipurpose Internet Mail Extension [MIME] type identifies the format of a file. Applications such as Internet browsers and email applications use the MIME type of a file to decide which actions to perform on it. For example, an email application can use the MIME type to detect the format of an attachment and choose an appropriate viewer for the file, such as opening a text document with gedit.

As another example, the Nautilus file manager needs to know the MIME type of a file to perform the following tasks:

- Open the file in an appropriate application.

- Display a string that describes the type of file.

- Display an appropriate icon to represent the file.

- Display a list of other applications that can open the file.

MIME types were originally proposed as a standard for identifying the message body of an e-mail message. Now, many systems use MIME types to identify the format of arbitrary files on the file system. MIME types are composed of a top-level media type followed by a subtype identifier, separated by a forward slash character, `/`. One example of a MIME type is `image/jpeg`. The media type in this example is `image` and the subtype identifier is `jpeg`. The top-level media type is meant to be a general categorization about the content of the file, while the subtype identifer is meant to specifically identify the format of the file.

There are eight media types currently blessed by the IANA [Internet Assigned Naming Authority]. These eight media types are

- application
- audio
- image
- message
- model
- multipart
- text
- video

. Many subtypes exist for each media type; for more information, see MIME Media Types at the IANA web site.

Implementation of MIME types in GNOME follows the XDG shared mime info specification. This specification provides the following advantages:

- Standard locations for all MIME related files.

- A standard way for applications to register information about a new MIME type.

- A standard way to retrieve the MIME type for a file.

- A standard way to retrieve information about a MIME type.

The rest of the chapter describes the files and directories that make up the MIME database, details about source XML files, how to create or modify MIME types, how to register applications as handlers for certain MIME types and finally, how to add an application to the GNOME desktop.

### The MIME Database

The MIME database is a collection of files that make up:

- The set of known MIME types

- The method for determing the MIME type of a file

- Meta information regarding a MIME type, such as a human readable description to use when displaying files of this type.

#### Location

As an administrator, the most important and basic step to understanding the MIME system is learning the locations where these files are stored. Since the XDG shared mime info specification was drafted by the X Desktop Group, it also makes use of the XDG base directory specification. It is highly recommended that you familiarize yourself with this specification, as it is also important for other system administration tasks such as editing menus. A brief summary of the directory locations as pertaining to the MIME specification is given below.

The MIME database is created from the set of files located in the `$XDG_DATA_HOME/mime` and `$XDG_DATA_DIRS/mime` directories. If these environment variables are unset, then they default to the values `~/.local/share` and `/usr/local/share:/usr/share` respectively. As can be seen from the default value for `$XDG_DATA_DIRS` , each environment variable is actually a colon separated list of directories. The user's database at `$XDG_DATA_HOME/mime` has precedence over the system database at `$XDG_DATA_DIRS/mime` when conflicting definitions are encountered. Similar to the XDG shared mime specification, we will refer to this set of directories as `<MIME>` in the rest of this document.

For example, assuming default paths for the environment variables, Load `<MIME>/text/plain.xml` means to load the following files:

- `~/.local/share/mime/text/plain.xml`

- `/usr/local/share/mime/text/plain.xml`

- `/usr/share/mime/text/plain.xml`

#### Contents

The following is a list of directories and files that are found inside the MIME database along with brief descriptions:

`<MIME>/packages/`

  This directory contains any number of XML files, each of which describe a collection of MIME types. By default, the `freedesktop.org.xml` file is installed in the `/usr/share/mime/packages` directory. This file contains all the default MIME types that are widely used and recognized.

  Applications which provide information about new MIME types are to install a single new XML file here. Depending on the prefix where the application is installed, it will create the file in the `/mime/package` subdirectory of one of the directories in `$XDG_DATA_HOME:$XDG_DATA_DIRS`. For example, an application installed to `/usr/bin` should install a new source XML file to the `/usr/share/mime/packages` directory. For more information about the XML files in the `packages` directory, please see .

`<MIME>/MEDIA/SUBTYPE.xml`

  These directories and files are automatically generated from the collection of source XML files in the `<MIME>/packages/` subdirectory by the update-mime-database application. For example, for each `mime-type` element in the `/usr/share/mime/packages/freedesktop.org.xml` file, a directory is created at `/usr/share/mime/` with the media type of the MIME type. An XML file is created in that directory with the subtype identifier of that MIME type as well. The contents of the created XML file include comments (and translations for them), subclasses designations and aliases.

  ##### Example: `/usr/share/mime/text/plain.xml` file

      <?xml version='1.0' encoding='utf-8'?>
      <mime-type xmlns="http://www.freedesktop.org/standards/shared-mime-info" type="text/plain">
      <!--Created automatically by update-mime-database. DO NOT EDIT!-->
        <comment>plain text document</comment>
        <!-- possibly more translations -->
        <comment xml:lang="es">documento de texto sencillo</comment>
        <comment xml:lang="eu">testu soileko dokumentua</comment>
        <comment xml:lang="fi">perustekstiasiakirja</comment>
        <comment xml:lang="fr">document plein texte</comment>
        <!-- possibly more translations -->
      </mime-type>

  This file is generated by the update-mime-database application, using the default source XML file `freedesktop.org.xml`.
`<MIME>/globs`

  Contains one line with a MIME type and a glob pattern, separated by a colon. Files which match the glob pattern are resolved to the MIME type specified before the colon. There are special rules about how filenames are matched by the glob pattern; for more details see the XDG shared mime specification.

  This file is also generated by the update-mime-database application, using the default source XML file `freedesktop.org.xml`.

`<MIME>/magic`

  A binary file which contains information on how to resolve MIME types by sniffing the content of the file. This is generally a set of one or more rules such as check for the string `%PDF-` at byte offset 0 in the file; if found, assign it the MIME type `application/pdf`.

  This file is also generated by the update-mime-database application.

`<MIME>/XMLnamespaces`

  Contains a mapping of XML namespaces to MIME types. Each line contains three fields, the namespace, the localName and the MIME type. Each field is separated by a space. If the localName is empty, then there are two spaces between the namespace and the MIME type.

  This file is also generated by the update-mime-database application.

`<MIME>/aliases`

  Contains a list of aliases for each MIME type. An alias is simply a MIME type that is sometimes known as another type. For each line in this file there are two fields: the first field is the alias name, and the second field is the MIME type. The fields are separated by a space.

  This file is also generated by the update-mime-database application.

`<MIME>/subclasses`

  Contains a list of subclassed MIME types and their parent MIME type. From the XDG shared mime specification:

  > A type is a subclass of another type if any instance of the first type is also an instance of the second. For example, all image/svg files are also text/xml, text/plain and application/octet-stream files. Subclassing is about the format, rather than the catagory of the data (for example, there is no 'generic spreadsheet' class that all spreadsheets inherit from).

  The format of this file is similar to the `aliases` file. Each line contains two fields, where the first field is the subclassed MIME type and the second field is the parent MIME type. Each field is separated by a space.

  This file is also generated by the update-mime-database application.

#### Refreshing the MIME Database

Understanding how to refresh the MIME database is important for administrators who wish to add new MIME types to the system, or otherwise modify information about a MIME type. The application update-mime-database is intended for this purpose.

For example, if an application installs information about a new MIME type to `/usr/share/mime/packages/diff.xml`, then update-mime-database must be called with the parameter `/usr/share/mime`.

    # update-mime-database /usr/share/mime
    ***
    * Updating MIME database in /usr/share/mime...
    ***

The MIME database is refreshed by scanning all the source XML files in the directory `<MIME>/packages`.

### The source XML files

Located in the `<MIME>/packages` directory, these XML files provide all the information regarding MIME types that is installed into the database by the update-mime-database application. There are a few rules about the XML file itself:

- It must specify the namespace as `http://www.freedesktop.org/standards/shared-mime-info`

- The root element must be `mime-info`

- Zero or more `mime-type` elements can be specified as children of the `mime-info` element. The `type` attribute is used to specify the MIME type that is being defined.

By default, the `freedesktop.org.xml` file is installed to the `packages` directory in one of the `<MIME>` paths (usually `/usr/share/mime/packages`).

gives a brief description for each of the elements that can occur as children to the `mime-type` element.

#### Child elements of `<mime-type>`

Element (and attributes) | Description
--- | ---
`<glob pattern="*.xyz">` | This element specifies a glob pattern against filenames. If the filename matches, then it is assigned the MIME type of the parent `mime-type` element. The `pattern` attribute is mandatory.

`<magic priority="50">`

This element contains a list of `match` elements as its children. The `priority` attribute is optional, and specifies a priority between 0 and 100, with 100 being the highest matching priority. Each child `match` element has three required attributes:

- `type`
- `offset`
- `value`

and a fourth optional attribute, `mask`. For details on these attributes, see the XDG shared mime info specification.

`<alias type="media/subtype">` | This element defines an alias for the parent `mime-type` element. An alias is simply a MIME type that is sometimes known as another type. For example, `application/x-pdf` is an alias for the MIME type `application/pdf`.
`<sub-class-of type="media/subtype">` | This element defines the parent `mime-type` element as a subclass of the MIME type specified in the `type` attribute. For example, `image/svg` is a sub class of the MIME type `text/xml`, `text/plain`, and `application/octet-stream`.
`<comment xml:lang="locale">` | This element provides a human readable description for the MIME type. There can be zero or more occurrences of this element as long as each one contains a unique value for the `xml:lang` attribute.

`<root-XML namespaceURI="namespace" localName="">`

If a file is determined to an XML file, then this element helps to further classify it through the use of the `namespaceURI` and `localName` attributes, both of which are required. The attribute `namespaceURI` is the namespace of the document, and `localName` is the name of the root element for the document. If `localName` is present but its value is empty, then the root element may have any name, but the namespace must still match.

The easiest way to understand these files is to take a look at an example. Borrowing from the XDG shared mime specification, displays the contents of a source XML file called `diff.xml`. This example defines the MIME type `text/x-diff`. There are multiple `comment` elements which give a human readable name to the MIME type in a number of different languages. This MIME type has both rules for matching through glob patterns and through the use of content sniffing (better known as `magic` rules). Any file with the extension `.diff` or `.patch` will resolve to this MIME type. Additionally any file whose contents start with the strings specified in the `value` attributes of the `match` element, will resolve to the `text/x-diff` MIME type.

The order in which glob patterns and magic rules apply is beyond the scope of this document. For details on this, see the XDG shared mime info specification.

#### Example of a source XML file: `diff.xml`

    <?xml version='1.0'?>
    <mime-info xmlns='http://www.freedesktop.org/standards/shared-mime-info'>
      <mime-type type="text/x-diff">
        <comment>Differences between files</comment>
        <comment xml:lang="af">verskille tussen lêers</comment>
        <!-- more translated comment elements -->
        <magic priority="50">
          <match type="string" offset="0" value="diff\t"/>
          <match type="string" offset="0" value="***\t"/>
          <match type="string" offset="0" value="Common subdirectories: "/>
        </magic>
        <glob pattern="*.diff"/>
        <glob pattern="*.patch"/>
      </mime-type>
    </mime-info>

### Modifying MIME types

You should never directly modify the source XML files that are installed to the `<MIME>/packages` directory by applications. Instead, modify the `Overrides.xml` file. This file has precedence over all other source XML files installed into the same `packages` directory. If you are an application author, then this rule does not apply. You should create a new source XML file and place it in the proper `<MIME>/packages` directory (your `Makefile` will take care of this, of course).

You can modify the MIME database for all users on the system or for a particular user depending on the location of the file you change. To modify the database for all users, make changes to the file `Overrides.xml` in the `$XDG_DATA_DIRS/mime/packages` directory. To modify the database for a single user, make changes to the file `Overrides.xml` in the `$XDG_DATA_HOME/mime/packages` directory.

After changes are made, you must always run the update-mime-database application, with the directory location of the MIME database as the first parameter.

#### Adding or Modifying MIME types

To add one or more MIME types for all users:

1. Create or modify an existing `Overrides.xml` source XML file, containing the definitions for the MIME types. For more information, see .

2. Place the `Overrides.xml` file in the `/usr/share/mime/packages` directory.

3. Update the MIME database by running update-mime-database using the system account.

       update-mime-database /usr/share/mime

To add one or more MIME types for a single user, follow the same steps, except place your `Overrides.xml` file in the `~/.local/share/mime/packages` directory. Additionally, call update-mime-database with `~/.local/share/mime/packages` as the first parameter.

#### Verifying Changes

After you have made a change to the MIME database and refreshed its contents, you can verify that the change has taken effect using the gnomevfs-info application. This application prints the MIME type and other useful information about a file.

Running gnomevfs-info on a SVG file gives you the output shown below. You'll notice the default application for this MIME type is `eog.desktop`; We will discuss default applications in .

    $ gnomevfs-info mime-diagram.svg
    Name              : mime-diagram.svg
    Type              : Regular
    MIME type         : image/svg+xml
    Default app       : eog.desktop
    Size              : 14869
    Blocks            : 32
    I/O block size    : 4096
    Local             : YES
    SUID              : NO
    SGID              : NO
    Sticky            : NO
    Permissions       : 600644
    Link count        : 1
    UID               : 1000
    GID               : 100
    Access time       : Wed Feb 22 18:24:47 2006
    Modification time : Wed Feb 22 18:24:42 2006
    Change time       : Wed Feb 22 18:24:42 2006
    Device #          : 775
    Inode #           : 297252
    Readable          : YES
    Writable          : YES
    Executable        : NO
    $

walks through the steps of creating a new MIME type and then verifying the changes using gnomevfs-info.

#### `application/x-newtype` Example

To create (or override) a MIME type and verify the changes:

1. Make a new, empty file in your home directory called `testing.xyz`.

2. Use gnomevfs-info on the file to find out the MIME type.The MIME type for this file should be detected as `text/plain` because there are not any glob patterns or magic rules that match it When no glob patterns or magic rules match a file, then it is resolved to the MIME type `text/plain` if it contains textual data or `application/octet-stream` for binary data. If the file is empty, then it defaults to `text/plain`. .

3. Create (or modify) the `Overrides.xml` file as described in with the contents given in .

4. Refresh the database using update-mime-database.

5. Use gnomevfs-info to verify that your change has taken effect. You should see the MIME type for the `testing.xyz` file resolved as `application/x-newtype`.

       $ gnomevfs-info testing.xyz | grep MIME
       MIME type         : application/x-newtype
       $

##### `Overrides.xml` file

    <?xml version='1.0' encoding='utf-8'?>
    <mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
      <mime-type type="application/x-newtype"><comment>new mime type</comment><glob pattern="*.xyz"/></mime-type>
    </mime-info>

### Registering Applications for MIME Types

Registering applications to handle MIME types is fairly straightforward. Applications are registered by creating a `MimeType` key in their `.desktop` entry file and listing each MIME type separated by a semicolon. The `MimeType` key should only be used in `.desktop` files whose `Type` key has the value `Application`. For more information on `.desktop` files, see .

After creating or modifying a `.desktop` entry file, you must update the application database using the update-desktop-database application (very similar to update-mime-database, except it does not take a parameter). This will create a `mimeinfo.cache` file in the `applications` subdirectory for each directory in `$XDG_DATA_HOME:$XDG_DATA_DIRS`. The cache file is necessary so that all the `.desktop` files do not need to be scanned for just the `MimeType` key, as this causes unnecessary disk I/O.

Default applications to use for specific MIME types should be specified in a file called `defaults.list`. This file is located in the `applications` subdirectory for each directory in `$XDG_DATA_HOME` and `$XDG_DATA_DIRS`. The format for this file consists of the MIME type, the `=` symbol and the Desktop File ID (which is the filename for the desktop entry file). is a short example of a `defaults.list` file in a user's `~/.local/share/applications` directory.

#### A User's `defaults.list` file

    [Default Applications]
    application/pdf=evince.desktop
    text/html=epiphany.desktop
    text/plain=gedit.desktop
    image/jpeg=eog.desktop
    image/png=eog.desktop
    text/xml=gedit.desktop

#### XDG Desktop Entry Specification

How to register MIME types for applications is part of the XDG desktop entry specification, rather than the XDG shared mime info specification.

### Adding an Application to the GNOME Desktop

To add an application to the GNOME Desktop, perform the following steps:

1. Add a menu item for the application. For more information on how to add an item to a menu, see .

2. Add an icon for the application to `/usr/share/icons/theme-name/icon-size/apps`. For more information on icons and themes, see .

3. If the application uses a new MIME type, add a source XML file to the MIME database. For more information, see .

4. If the application uses a new MIME type, add an icon for the MIME type to `/usr/share/icons/theme-name/icon-size/mimetypes`. For more information on icons and themes, see .

5. To associate the application with a MIME type, include a `MimeType` key in your `.desktop` file. For more information, see .

## Setting Screensavers

This chapter describes how to set preferences for the screensaver. This chapter also provides information on how to modify the displays that are available for the screensaver.

### Introduction to Screensavers

A screensaver is an application that replaces the image on a screen when the screen is not in use. The screensaver application for the GNOME Desktop is gnome-screensaver. The following sections describe how to set preferences for the gnome-screensaver application, and how to change the themes that are available for the screensaver.

### Setting Screensaver Preferences

All screensaver preferences and settings are stored in GConf.

To modify screensaver application preferences, users can use the Screensaver preference tool. For information on screensaver preferences, see GNOME Desktop User's Guide.

Users can also run the command `/usr/bin/gnome-screensaver-preferences` to open the Screensaver Preferences dialog.

To set default screensaver settings and policy for all users, modify the screensaver settings in the Default GConf Configuration Source.

To set mandatory screensaver settings and policy for all users, modify the screensaver settings in the Mandatory GConf Configuration Source.

### Modifying Screensaver Themes

The screensaver application allows users to choose one or more screensaver themes. A screensaver theme is an application that displays images on the screen of the user when the screen is not in use. The available screensaver themes are listed in the Screensaver preference tool.

To add a new screensaver theme, copy the executable file for the screensaver theme engine to somewhere in your PATH or into the screensaver theme engine executable directory. The screensaver theme engine executable directory for your system can be determined using the following command:

    pkg-config --variable=privlibexecdir gnome-screensaver

Next, add a `.desktop` file for the theme into the screensaver themes directory. The screensaver themes directory for your system can be determined using the following command:

    pkg-config --variable=themesdir gnome-screensaver

In the Exec field of the `.desktop` file include any arguments that are required to run the screensaver theme on the whole screen, rather than in a window. For example, some legacy screensaver theme engines may require you to include the `-root` option to display the screensaver display on the whole screen.

The Screensaver infrastructure implements themes according to the XDG menu specification. By supporting this specification, GNOME allows you to:

- Customize the themes easily. You can edit a small number of files to customize the available themes. You do not need to modify your applications or move files.

- Install themes easily. You do not need to provide information about the system when you install the themes.

- Configure the system so that users cannot modify the themes.

For more information, see .

## Session Management

This chapter introduces session management, and describes how to set session defaults. The chapter also contains information on sessions and login scripts.

### Introduction to Sessions

A session occurs between the time that a user logs in to the GNOME Desktop and the time that the user logs out. The session manager starts after the Login Manager authenticates the user. The session manager enables the user to manage the session. For example, a user can save the state of a session and return to that session the next time that the user logs in.

At a minimum, the following applications run in a session:

- The session manager, `gnome-session`.

- The GConf X settings daemon, `gnome-settings-daemon`.

- The gnome-panel application, which runs the panels in the GNOME Desktop.

- The Metacity window manager.

### Setting Session Defaults

The following table lists the files that contain default session information:

File | Description
--- | ---
`/usr/share/gnome/default.session` | Default session file. Default session details are stored in this file.
`$HOME/.gnome2/session` | User session file. When a user modifies the session, the details are stored in this file.

To set default session details for all users, modify the default session file.

To restore the default session settings for a user, delete the session file from the home directory of the user. If no user session file is present, the default settings in `/usr/share/gnome/default.session` are used.

To save the current session as the default session, users can run the `gnome-session-save` command.

## Help System

This chapter describes the Help system in the GNOME Desktop.

### Introduction to the Help System

The GNOME Desktop displays help in the Yelp Help browser. For more information, see Yelp Help Browser in the GNOME Desktop User Guide.

The source documents for the help are XML files. The XML files are written to the DocBook XML Version 4.1.2 document type definition (DTD). The DocBook XML files are converted to HTML using stylesheets installed with gnome-doc-utils and the HTML is displayed in the help browser. For more information on DocBook XML, see the following URL:

          http://www.oasis-open.org/docbook/xml

The Help system uses Open Source Metadata Framework (OMF) files, and a cataloging system. The next sections describe OMF files and the cataloging system.

### OMF Files

The XML file for each manual has an associated OMF file. The OMF file contains information about the manual that is used by the Help browser. OMF files have a `.omf` extension.

When you install an application, the installation process installs an OMF file to a directory of OMF files. If a Help document has an associated OMF file in an OMF file directory, the Help document is displayed in the Help browser.

OMF files contain information about Help documents such as the following:

- The location of the XML file for the Help document

- The title of the Help document

- A subject category to which the Help document belongs

For more information on how to create OMF files, please see Writing Scrollkeeper OMF Files.

### ScrollKeeper Cataloging System

ScrollKeeper is a cataloging system for documentation. Its primary function is to manage the information in OMF files for the help browser. When you install an application, the OMF file is copied to the `$prefix/share/omf/<application-name>` directory.

ScrollKeeper builds a table of contents from the collection of OMF files in the directories specified in `$prefix/etc/scrollkeeper.conf` file. This file usually consists of a single line with the `OMF_DIR` set to a comma separated list of directories to recursively search.

    OMF_DIR=/usr/share/omf:/usr/local/share/omf:/opt/gnome2/share/omf:/opt/kde/omf

ScrollKeeper contains a hierarchy of subject categories to which a help document can belong. The subject category of the document in the OMF file determines the location of the document in the table of contents presented by the help browser.

The hierarchy of subject categories is defined in the file `$prefix/scrollkeeper/Templates/<lang>/scrollkeeper_cl.xml`. The subject category of a document must correspond to a category specified in this file.

For more information on the Scrollkeeper system, visit the website at http://scrollkeeper.sourceforge.net/.

If the help document XML file is moved to a new location, then the location in the OMF file needs to be updated.

## Improving Performance

This chapter describes how to improve the performance of the GNOME Desktop.

### Introduction to Improving Performance

This chapter lists several preferences whose settings you can change to improve the performance of the GNOME Desktop. You can use the `gconftool-2` command to set values for preferences for users. The example commands in this chapter show how to set values in the user configuration source.

You can also use the `--direct` and `--config-source` options to set mandatory values or default values for preferences. You can also use the `gconftool-2` command in a script to set the values of many preferences. For more information on the `gconftool-2` command and the options that are available with the command, see .

### Reducing CPU Usage

This section describes preferences that you can set to reduce CPU usage by the GNOME Desktop.

#### To Use Theme Options Which Require Less CPU Resources

Some window frame theme options load image files to draw the window frame. Other options use simpler techniques to draw the window frame.

The Crux window frame option loads image files, and can be slow on systems with limited CPU resources. To reduce CPU usage, use one of the following window frame options:

- Atlanta

- Esco

The following window frame options also use less CPU resources than Crux:

- AgingGorilla

- Bright

- Metabox

Metabox does not work well with inverse controls options such as HighContrastInverse. Use Atlanta with inverse controls options.

To change the window frame theme option, run the following command:

    gconftool-2 \
    --type string \
    --set /apps/metacity/general/theme option-name

For example, to use Atlanta, run the following command:

    gconftool-2 \
    --type string \
    --set /apps/metacity/general/theme Atlanta

Alternatively, users can use the Theme preference tool to select the appropriate option.

You can use the Metacity Theme Viewer to measure the performance of a window frame option, and to preview the option. To start Metacity Theme Viewer, use the following command:

    metacity-theme-viewer option-name

For example, to measure the performance of Atlanta and preview Atlanta, run the following command:

    metacity-theme-viewer Atlanta

#### To Reduce CPU Usage by Turning Off Display of Icons in Menus

Some items in menus display an icon beside the item. To turn off this feature, run the following command:

    gconftool-2 \
    --type bool \
    --set /desktop/gnome/interface/menus_have_icons false

Alternatively, users can use the Menus & Toolbars preference tool to deselect the Show icons in menus option.

#### To Reduce CPU Usage by Turning Off the Splash Screen

By default, when users log in to the desktop environment, a splash screen is displayed. Icons are displayed on the splash screen while the user logs in. You can turn off the splash screen to reduce CPU usage during login.

To turn off the splash screen, run the following command:

    gconftool-2 \
    --type bool \
    --set /apps/gnome-session/options/show_splash_screen false

Alternatively, users can use the Sessions preference tool to deselect the Show splash screen on login option.

#### To Reduce CPU Usage by Turning Off Panel Animation

When users show or hide panels, the panels can show or hide in an animated style. To turn off panel animation, run the following command:

    gconftool-2 \
    --type bool \
    --set /apps/panel/global/enable_animations false

Alternatively, users can use the Panel preference tool to deselect the Drawer and panel animation option.

#### Improving File Manager Performance

The Nautilus file manager includes some features that you can modify to improve performance.

##### To Modify Performance Preferences

The file manager includes performance-related preferences. Each performance preference can take one of three values. The values are described in the following table:

Value | Description
--- | ---
`always` | Performs the action for both local files, and files on other file systems.
`local_only` | Performs the action for local files only. When you set a performance preference to `local_only`, the CPU usage is reduced.
`never` | Never performs the action. When you set a performance preference to never, the CPU usage and the network traffic are reduced.

The following table describes the performance preferences for the file manager. For the fastest performance, set the value of the preferences to `never`.

Preference | Description
--- | ---

`show_icon_text`

Specifies when to preview the content of text files in the icon that represents the file. To never preview the content of text files, run the following command:

    gconftool-2 \
    --type string \
    --set /apps/nautilus/preferences/show_icon_text never

Alternatively, users can perform the following steps:

1. Choose Edit Preferences from a file manager window, then choose Preview.

2. Select an option for the Show text in icons preference.

`show_directory_item_counts`

Specifies when to show the number of items in folders. To never show the number of items in folders, run the following command:

    gconftool-2 \
    --type string \
    --set /apps/nautilus/preferences/show_directory_item_counts never

Alternatively, users can perform the following steps:

1. Choose Edit Preferences from a file manager window, then choose Preview.

2. Select an option for the Count number of items preference.

`show_image_thumbnails`

Specifies when to show thumbnails of image files. To never show thumbnails, run the following command:

    gconftool-2 \
    --type string \
    --set /apps/nautilus/preferences/show_image_thumbnails never

Alternatively, users can perform the following steps:

1. Choose Edit Preferences from a file manager window, then choose Preview.

2. Select an option for the Show thumbnails preference.

`preview_sound`

Specifies when to preview the content of sound files. To never preview the content of sound files, run the following command:

    gconftool-2 \
    --type string \
    --set /apps/nautilus/preferences/preview_sound never

Alternatively, users can perform the following steps:

1. Choose Edit Preferences from a file manager window, then choose Preview.

2. Select an option for the Preview sound files preference.

##### To Turn Off the Side Pane, Toolbar, and Location Bar

The file manager includes preferences that enable you to turn off the side pane and the toolbar. To improve file manager performance, turn off the side pane and the toolbar.

To turn off the side pane, run the following command:

    gconftool-2 \
    --type bool \
    --set /apps/nautilus/preferences/start_with_sidebar false

To turn off the toolbar, run the following command:

    gconftool-2 \
    --type bool \
    --set /apps/nautilus/preferences/start_with_toolbar false

You can also turn off the location bar. Users can use the CtrlL keyboard shortcut to display a location bar when required.

To turn off the location bar, run the following command:

    gconftool-2 \
    --type bool \
    --set /apps/nautilus/preferences/start_with_location_bar false

##### To Turn Off the Desktop

The file manager contains a preference that enables users to use Nautilus to manage the desktop. You can disable the desktop to improve performance. However, if you disable the desktop, you cannot do the following:

- Use the file manager to change the pattern or color of the desktop background.

- Use the desktop objects, such as Trash. The desktop objects are not displayed on the desktop.

To disable the desktop, run the following command:

    gconftool-2 \
    --type bool \
    --set /apps/nautilus/preferences/show_desktop false

### Reducing X Window System Network Traffic

This section describes preferences that you can set to reduce X Window System network traffic on the GNOME Desktop.

#### To Use Theme Options Which Create Less Network Traffic

Remote display protocols do not transfer every pixel in a block of pixels if all pixels in the block are the same color.

To reduce X Window System network traffic, use a window frame theme option that uses solid colors. That is, use one of the following window frame options:

- Atlanta

- Esco

For information on how to change theme options, see .

#### To Reduce Network Traffic by Turning Off Display of Icons in Menus

Some items in menus display an icon beside the item. If the icon is located on another file system, this feature can increase X Window System network traffic. This feature can also increase X Window System network traffic if the panels are displayed on a remote host.

For information on how to turn off this feature, see .

### Reducing Color Usage and Improving Display Quality

Many modern computer systems support 24-bit color, that is, 16,777,216 colors. However, many users still use systems that support 8-bit color, that is, 256 colors.

The GNOME Desktop uses the websafe color palette. This palette is a general-purpose palette of 216 colors, which is designed to optimize the use of color on systems that support 8-bit color. However, some visual components of the GNOME Desktop are designed for systems that support 24-bit color.

The following display problems might occur on systems that support 8-bit color:

- Windows, icons, and background images might appear grainy. Many themes, background images, and icons use colors that are not in the websafe color palette. The colors that are not in the palette are replaced with the nearest equivalent or a dithered approximation. This use of replacement colors causes the grainy appearance.

- Applications that do not use the websafe color palette have less colors available. Color errors might occur. Some colors might not appear in the user interface of the application. Some applications might crash if the application cannot allocate colors.

- Color flashing might occur when users switch between applications that use the websafe color palette, and applications that do not use this palette. The applications that do not use the websafe color palette might use a custom colormap. When the custom colormap is used, other visual components might lose colors, then become unviewable.

The following sections describe how to optimize the appearance of the GNOME Desktop for systems that support 8-bit color.

#### To Use Theme Options That Use the Websafe Color Palette

Some window frame theme options use colors that are in the websafe color palette. Bright and Esco use colors from the websafe color palette. Bright and Esco do not have the grainy appearance of other window frame options on 8-bit color displays. Use Bright or Esco for the best color display on 8-bit visual modes.

For information on how to change theme options, see .

#### To Reduce Color Usage by Turning Off Display of Icons in Menus

Some items in menus display an icon beside the item. If the icon contains colors that are not in the websafe color palette, this feature can increase the number of colors used.

For information on how to turn off this feature, see .

#### To Reduce Color Usage by Turning Off the Splash Screen

You can turn off the splash screen to make more colors available for the GNOME Desktop and for applications.

For information on how to turn off the splash screen, see .

#### To Reduce Color Usage by Using a Solid Color for the Background

Use a solid color for the desktop background. Use of a solid color reduces the number of colors used by the GNOME Desktop.

To set a solid color for the background, run the following commands:

    gconftool-2 \
    --type string \
    --set /desktop/gnome/background/picture_options none

    gconftool-2 \
    --type string \
    --set /desktop/gnome/background/color_shading_type solid

    gconftool-2 \
    --type string \
    --set /desktop/gnome/background/primary_color #hexadecimal-color

Alternatively, users can use the Background preference tool to choose a solid color for the background.

## Disabling GNOME Desktop Features

This chapter describes how to disable particular features of the GNOME Desktop.

### Introduction to Disabling GNOME Desktop Features

The GNOME Desktop includes features that you can use to restrict access to certain functions in the GNOME Desktop. The disable features are useful in various situations where you want to restrict the actions that users can perform on a computer. For example, you might want to prevent command line operations on a computer that is for public use at a trade show. The disable features are also known as lockdown features.

You set GConf keys to disable features. For information about how to set GConf keys, see . You can also use the Configuration Editor application to set GConf keys in a user configuration source. For more information about the Configuration Editor application, see the GConf Editor Manual.

### Locking Down Setting Manually

#### To Disable Lock Screen and Log Out

To disable the lock screen and log out functions, set the `/apps/panel/global/disable_lock_screen` key and the `/apps/panel/global/disable_log_out` key to `true`.

When you disable the lock screen and log out functions, the following items are removed from the panels:

- Lock Screen and Log Out user menu items from the Main Menu.

- Lock and Log Out menu items from the Add to Panel Actions menu. To open this menu, right-click on a vacant space on a panel, then choose Add to Panel Actions.

- Lock Screen and Log Out user menu items from the Actions menu in the Menu Bar applet.

Also, any Lock Screen buttons and Log Out buttons on panels are disabled.

#### To Disable Command Line Operations

To disable operations from a command line, set the `/desktop/gnome/lockdown/disable_command_line` key to `true`.

When you disable command line operations, the following changes occur in the user interface:

- The Run Application menu item is removed from the following menus:

  - Main Menu

  - Actions submenu in the Add to Panel menu

  - Actions menu in the Menu Bar applet

- Any Run buttons on panels are disabled.

To disable command line operations, you must also remove menu items that start terminal applications. For example, you might want to remove menu items that contain the following commands from the menus:

- GNOME Terminal command, that is `/usr/bin/gnome-terminal`

- `/usr/bin/xterm`

- `/usr/bin/setterm`

The items are removed from the following menus:

- Main Menu

- Add to Panel Launcher from menu

To disable command line operations, you must also disable the Command Line applet. To disable the Command Line applet, add the applet to the `/apps/panel/global/disabled_applets` key. When you disable the Command Line applet, the Command Line applet is removed from the Main Menu and the Add to Panel Utility menu.

#### To Disable Panel Configuration

To disable panel configuration, set the `/apps/panel/global/locked_down` key to `true`.

When you disable panel configuration, the following changes occur in the user interface:

- The following items are removed from the panel popup menu, and from the drawer popup menu:

  - Add to Panel

  - Delete This Panel

  - Properties

  - New Panel

- The launcher popup menu is disabled.

- The following items are removed from the applet popup menu:

  - Remove From Panel

  - Lock

  - Move

- The Main Menu popup menu is disabled.

- The launcher drag feature is disabled, so that users cannot drag launchers to, or from, panels.

- The panel drag feature is disabled, so that users cannot drag panels to new locations.

### Lockdown Editor

As of GNOME 2.14, a graphical lockdown editor called Pessulus has been included to ease the task of disabling desktop settings.

#### Getting Started

To run the lockdown editor:

- Click the System Administration Lockdown Editor

- Run the `pessulus` command in a terminal window.

You will see a window with several different tabs. Each of the tabs represents a different category of desktop settings that can be disabled. In the next section, we will discuss each category and provide a brief description for each setting that can be disabled.

#### Disabling Features

To disable a setting, make sure the checkbox next to the setting's description is checked. Most settings will take effect immediately, however some settings will require that the application be restarted in order to take effect.

When pessulus starts, it will try to get a connection to the GConf mandatory configuration source. This address for this configuration source is `xml:merged:$prefix/etc/gconf/gconf.xml.mandatory`. If the user that is running pessulus has access to this configuration source, then a lock icon will be displayed next to the checkbox for each setting. Clicking the lock will toggle whether or not the setting is mandatory. If the setting is mandatory, then regular users will not be able to change or override the setting. If the user running pessulus does not have access to the mandatory configuration source, then the lock icon will not appear. In this case, all disabled settings will simply be stored in the user's default configuration source and can be modified later using other tools such as gconf-editor or gconftool-2. For more information on GConf and mandatory configuration sources, see .

The following subsections will give a brief description of the settings that can be disabled for each category.

Depending on the applications you have installed, you may see fewer categories than those described in this section.

##### General

Disable command line

  Prevent the user from accessing the terminal or specifying a command line to be executed. For example, this would disable access to the panel's "Run Application" dialog.

Disable printing

  Prevent the user from printing. For example, this would disable access to all applications' "Print" dialogs.

Disable print setup

  Prevent the user from modifying print settings. For example, this would disable access to all applications' "Print Setup" dialogs.

Disable save to disk

  Prevent the user from saving files to disk. For example, this would disable access to all applications' "Save as" dialogs.

##### Panel

Lock down the panels

  If true, the panel will not allow any changes to the configuration of the panel. Individual applets may need to be locked down separately however. The panel must be restarted for this to take effect.

Disable force quit

  If true, the panel will not allow a user to force an application to quit by removing access to the force quit button.

Disable lock screen

  If true, the panel will not allow a user to lock their screen, by removing access to the lock screen menu entries.

Disable log out

  If true, the panel will not allow a user to log out, by removing access to the log out menu entries.

##### Epiphany Web Browser

Disable quit

  User is not allowed to close Epiphany.

Disable arbitrary URL

  Disable the user's ability to type in a URL to Epiphany.

Disable bookmark editing

  Disable the user's ability to add or edit bookmarks.

Disable history

  Disable all historical information by disabling back and forward navigation, not allowing the history dialog and hiding the most used bookmarks list.

Disable javascript chrome

  Disable JavaScript's control over window chrome.

Disable toolbar editing

  Disable the user's ability to edit toolbars.

Force fullscreen mode

  Locks Epiphany in fullscreen mode.

Hide menubar

  Hide the menubar by default. The menubar can still be accessed using F10.

Disable unsafe protocols

  Disables loading of content from unsafe protocols. Safe protocols are http and https.

##### GNOME Screensaver

Lock on activation

  Set this to TRUE to lock the screen when the screensaver goes active.

Allow log out

  Set this to TRUE to offer an option in unlock dialog to logging out after a delay. The Delay is specified in the "logout_delay" key.

Allow user switching

  Set this to TRUE to offer an option in the unlock dialog to switch to a different user account.

## Hidden Directories

This appendix describes the hidden directories that the GNOME Desktop adds to the home directories of users.

A hidden directory is a directory that has a name that begins with a period (.). describes the hidden directories that the GNOME Desktop adds to the home directories of users.

### Hidden Directories in User Home Directories

Directory | Description
--- | ---
`.config` | This is the default location for the environment variable `XDG_CONFIG_HOME`, if it is not set. User defined menus can be created at `menus/applications.menu`.
`.fonts` | Contains fonts specific to a particular user. When a user installs a font by dragging it to the `fonts:///` URI in nautilus, it is copied to this location.
`.esd_auth` | Contains the authentication cookie for the GNOME sound daemon. The GNOME sound daemon is the Enlightened Sound Daemon (ESD). NOTE: This is a file, not a directory.
`.gconf` | Contains the GConf configuration source for the user. When the user sets a preference, the new preference information is added to this location.

`.gconfd`

Contains the following GConf daemon details:

- Configuration information.

- Lock information for objects that are referenced by an Interoperable Object Reference (IOR).

- State information for objects that are referenced by an IOR.

`.gnome` | Contains user-specific application data that is not stored in the GConf repository. NOTE: this directory is deprecated and is only used by GNOME 1.x applications.

`.gnome2`

Contains user-specific application data that is not stored in the GConf repository. For example, this directory contains the following:

- Keyboard shortcut information.

- Window location information.

- Desktop entry files for panel launchers.

This directory may also contain sub-directories that store application specific data.

`.gnome2-private` | Ignore this directory. This directory has no function at the time of publication of this guide.
`.local/share` | This is the default location for the environment variable `XDG_DATA_HOME`, if it is not set. User defined desktop entries can be created in the subdirectory `applications`. User defined mime types can be created in `mime/packages/Overrides.xml`.
`.metacity` | Contains session data for the Metacity window manager.

`.nautilus`

Contains file manager data that is specific to the user. For example, this directory can contain the following:

- Metadata for the directories with which the user works.

- Nautilus emblems that the user adds.

- Nautilus desktop images.

`.themes` | Contains controls theme options, window frame theme options, and icons theme options that the user adds. The user can add themes from the Theme preference tool.
`.thumbnails` | Contains image thumbnails for the user. The image thumbnails are used in the file manager. The file manager contains a preference that the user can select to stop generation of thumbnail images.

## Security Note on Configuring SMB Printers

This appendix provides a security note related to the configuration of printers on Windows network shares.

Windows network shares are also referred to as Samba or SMB shares. When you configure a printer on an SMB share, you must enter a username and password for the print queue.

The username and password for the print queue is stored as unencrypted text in the file `/etc/cups/printers.conf`. This file has read-only permissions for users with root privileges, so any user with root privileges can read the username and password for the print queue.

To reduce the impact of possible security violations, ensure that the username and password required to access the print queue is used only for the print queue. This ensures that any possible security violation is restricted to unauthorized use of the print queue.

## Glossary

`.desktop` file
`.directory` file
`.omf` file
application registry

  The application registry is a collection of desktop entry files which register applications. The location of the application registry for the GNOME Desktop is `$XDG_DATA_DIRS:$XDG_DATA_HOME/applications/`.

desktop entry file

  A data file that provides information about an item in a menu. The desktop entry file specifies the details for the item such as a name, a command to run, an icon, and so on. Desktop entry files have a `.desktop` file extension.

directory entry file

  A data file that provides information about a menu. The directory entry file specifies details such as a name for the menu, a tooltip for the menu, and an icon to represent the menu. Directory entry files have a `.directory` file extension.

GConf configuration source

  A storage location in the GConf repository. For example, `xml:readonly:/etc/gconf/gconf.xml.defaults`.

GConf preference key

  An element in the GConf repository that corresponds to an application preference. For example, the `/apps/gnome-session/options/show_splash_screen` key corresponds to the Show splash screen on login option in the Sessions preference tool.

GConf path file

  A file that lists the GConf configuration sources, and the order in which to search the sources.

GConf schema

  A collective term for a schema key and a schema object.

GConf schema definition file

  A GConf schema definition file lists the keys in a particular application, and defines the characteristics of the keys. GConf schemas are generated from schema definition files. Schema definition files have a `.schemas` file extension.

GConf schema key

  A key that stores a schema object for a preference key. For example, `/schemas/desktop/gnome/interface/font_name` is a schema key for the `/desktop/gnome/interface/font_name` preference key.

GConf schema object

  An element in a configuration source that contains information about a preference key. The schema object contains information such as a default value for the preference key, and documentation on the preference key.

glob pattern

  A glob pattern is used to match a file name by using special characters such as `*` and `?`. The MIME system uses glob patterns to assign MIME types based upon filenames and often, file extensions.

Interoperable Object Reference

  An Interoperable Object Reference (IOR) is a string reference to a CORBA object. An IOR encodes a hostname and port to which messages can be sent to control the object. The IOR also contains an object key to identify the object.

magic rule

  A magic rule defines a file's MIME type by specifying text or binary data to search for at the beginning of the file. Offsets to look for this data are defined in a magic rule.

Menu definition files

  Menu definition files define the hierarchy of menus that are used in the GNOME menu bar.

MIME

  Multipurpose Internet Mail Extension.

MIME source XML file

  A MIME source XML file defines how MIME types are resolved for different kinds of files. There are three ways in which this can be done: using file extensions (glob patterns), using magic rules and using XML namespaces. MIME source XML files are located in the `$XDG_DATA_DIRS:$XDG_DATA_HOME/mime/packages` directory.

MIME type

  A MIME type identifies the format of a file. The MIME type enables applications to read the file. For example, an email application can use the `image/png` MIME type to detect that a Portable Networks Graphic (PNG) file is attached to an email.

MIME type database

  The MIME type database is a collection of files which register MIME types for the desktop environment. The location of the MIME type database is the directory `$XDG_DATA_DIRS:$XDG_DATA_HOME/mime`.

OMF file

  Open Source Metadata Framework file. This is a file that is associated with the XML file for a manual. The OMF file contains information about the manual that is used by the Help browser. OMF files have a `.omf` file extension.

PAM

  Pluggable Authentication Modules.

screensaver

  A screensaver is an application that replaces the image on a screen when the screen is not in use. The screensaver application for the GNOME Desktop is XScreenSaver.

screensaver display

  A screensaver display is an application that displays images on the screen of the user when the screen is not in use.

UDP

  User Datagram Protocol.

Uniform Resource Identifier

  A Uniform Resource Identifier (URI) is a string that identifies a particular location in a file system or on the web. For example, the address of a web page is a URI.

websafe color palette

  The websafe color palette is a general-purpose palette of 216 colors. The websafe color palette is designed to optimize the use of color on systems that support 8-bit color. The websafe color palette is also called the Netscape color palette and the Netscape color cube.