GConf is GNOME's configuration storage system. It is not tied to GNOME and can be used by any other program as well, though.

If you're looking for configuration for Gnome 2 user applications like Evolution, you'll find it in GConf. Settings are stored in .gconf/ by default (and not normally changed). You can edit the settings using gconf-editor if you want a GTK GUI or using gconftool from the CommandLine.

Comparisons with MicrosoftWindows's registry are inevitable. GConf is a database rather than a series of configuration files, but it's XML, it's open and it actually works.

The Windows registry fails because:

• It's very difficult to manage a large number of computers; system administrators can't install defaults, or push changes out to multiple user computers. Proprietary add-on tools exist that try to resolve this problem in various (rather frightening) ways.
• The registry contains lots of undocumented, cryptically-formatted data, and regedit is therefore dangerous and difficult to use.
• The registry becomes corrupted, and this tends to destroy the whole operating system installation.

GConf attempts to leapfrog the registry concept. It's a library which provides a simple configuration data storage interface to applications, and also an architecture that tries to make things easy for system administrators.

Here are some of the features of GConf:

Replaceable backend architecture

GConf currently has a single backend that stores configuration data in XML-format text files; however, the architecture allows a Registry-like binary database backend, an LDAP backend, or even a full-blown SQL database backend. The backend used is configurable by the system administrator. This is a valuable feature for IS deparatments managing large numbers of computers.

Configuration key documentation

Applications can install documentation along with their configuration data, explaining the possible settings and the effect of each configuration key. A regedit-style tool can display this documentation, making it much easier to customize applications without breaking them. The GConf database also stores useful meta-information such as the application that owns a key, when the key was last changed, etc.

Data change notification service

If configuration data is changed, all interested applications are notified. The notification service works across the network, affecting all login sessions for a single user.

This means that programs built from components (where each component may be in a separate process) are much easier to write, because if one component changes a setting the others can discover the change and update themselves. GNOME's Nautilus file manager f.ex. is actually a collection of applications, including an embedded web browser and various navigation components, which communicate via CORBA. However, you want a single preferences dialog located in the top-level "shell" component. Without GConf, a custom protocol would have to be invented for preferences settings to notify embedded components of changes to user preferences.

Notification is also useful if multiple application instances are running. GNOME 2.0 uses this feature to let user interface configuration take effect on-the-fly without restarting any applications; if you turn off toolbar icons, for example, toolbar icons will immediately disappear in all running apps.

See also: http://developer.gnome.org/feature/archive/gconf/gconf.html