KDE Kiosk Mode

When users misconfigure software by mistake, the help desk suffers too. Here's how to lock in sensible choices for important options.

starting kcalc with the Precision group set as immutable makes changing these values impossible. Figures 3 and 4 show the difference between the locked and unlocked kcalc Precision settings.

Figure 3. The kcalc General Settings Dialog with Locked Precision Settings

Figure 4. The kcalc General Settings Dialog with Unlocked Precision Settings

Finally, the whole configuration file for the application can be made immutable by placing a [$i] at the very top of the file. This immutable mark cascades to all group and key/value pairs contained within the file. Setting the configuration file to immutable in this fashion completely disallows any changes made to an application's configuration.

Alternatively, if the KDE application does not have write access to the configuration file, it also is considered to be an immutable configuration file. This file permission restriction can be set directly on configuration files in the KDEHOME directory to prevent a user from editing the configuration.

For example, saving a non-writable kickerrc file restricts users from making any changes to the kicker panel. Many other KDE applications follow a similar procedure, though a restart of the application may be required in order for it to re-read its new configuration.

Figure 5. A kicker with its configuration file marked as immutable. It has a noticeable lack of handles, which allows the applets contained within to be customized.

Figure 6. The Normal Kicker

Action Restrictions

On top of being able to lock configuration items for users, administrators also can remove the functionality of certain actions users can perform. An action is simply something the user can perform, such as File→New. Because most KDE applications provide common actions, predefined standard action restrictions are easy to lock down. Program action restrictions are configured in the kdeglobals file, located in the same configuration directory structure noted above.

The following code snippet disables the standard Help menu available from the main toolbar of KDE applications:

...
[KDE Action Restrictions][$i]
action/help=false
...

Figure 7. Konqueror with Help

Figure 8. Konqueror without Help

Another option is disabling the Bookmarks feature of Konqueror. This can be accomplished like this:

...
[KDE Action Restrictions][$i]
action/bookmarks=false
...

Not all action restrictions have to be menu items. For example, the following snippet disables any options that require root access:

...
[KDE Action Restrictions][$i]
user/root=false
...

Many more actions can be set. A more complete list can be found in the kiosk documentation. Many of the actions are standard across KDE applications. Some applications, however, provide their own local actions, which can be restricted as well. Some of the more interesting actions are:

  • print/system: disables the ability to select the printing system.

  • shell_access: disables ability to start up a shell.

  • logout: disables user logouts.

  • run_command: disables Alt-F2 run command.

  • lineedit_text_completion: disables lineedits from remembering previous entries for partial text completion.

Restricting Other Resources

On top of configuration files, KDE applications utilize other types of resources in the KDEDIRS directories. Similar to the configuration file examples above, these resources are extended by resource files installed in KDEHOME. KDE provides the ability to restrict access to these types of files as well. This configuration information is stored in the kdeglobals configuration file. For example, the following kdeglobals snippet limits users' ability to add and utilize custom icon sets other than the ones already existing in an upper-level resource directory:

...
[KDE Resource Restrictions][$i]
icon=false
...

A list of resource types defined by KDE is shown in Table 1.

Table 1. Resource Types

Resource Type Location
apps share/applnk
configshare/config
datashare/apps
exebin
htmlshare/doc/HTML
iconshare/icon
liblib
localeshare/locale
mimeshare/mimelnk
pixmapshare/pixmaps
servicesshare/services
servicetypesshare/servicetypes
soundshare/sounds
templatesshare/templates
wallpapershare/wallpapers
xdgdata-appsshare/applications
______________________

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