# The Registry

After Win3.x, the registry became a fundamental part of Windows. It is the place where both Windows itself, and all Win95/98/NT/2000/XP/etc.-compliant applications, store configuration and state data. While most sane system administrators (and Wine developers) curse badly at the twisted nature of the Windows registry, it is still necessary for Wine to support it somehow.

## The default registry

A Windows registry contains many keys by default, and some of them are necessary for even installers to operate correctly. The keys that the Wine developers have found necessary to install applications are distributed in a file called `winedefault.reg`. It is automatically installed for you if you use the `tools/wineinstall` script in the Wine source, but if you want to install it manually, you can do so by using the `regedit` tool to be found in the `programs/regedit/` directory in Wine source. `winedefault.reg` should even be applied if you plan to use a native Windows registry, since Wine needs some specific registry settings in its registry (for special workarounds for certain programs etc.). In the main Wine source code directory in a terminal, run:

      $ cd programs/regedit
      $ ./regedit ../../winedefault.reg

## Using a Windows registry

If you point Wine at an existing Windows installation (by setting the appropriate directories in `~/.wine/config`, then Wine is able to load registry data from it. However, Wine will not save anything to the real Windows registry, but rather to its own registry files (see below). Of course, if a particular registry value exists in both the Windows registry and in the Wine registry, then Wine will use the latter. In the Wine config file, there are a number of configuration settings in the [registry] section (see below) specific to the handling of Windows registry content by Wine.

## The Registry

The initial default registry content to be used by the Wine registry files is in the file `winedefault.reg`. It contains directory paths, class IDs, and more; it must be installed before most `INSTALL.EXE` or `SETUP.EXE` applications will work.

## Registry structure

The Windows registry is an elaborate tree structure, and not even most Windows programmers are fully aware of how the registry is laid out, with its different "hives" and numerous links between them; a full coverage is out of the scope of this document. But here are the basic registry keys you might need to know about for now.

HKEY_LOCAL_MACHINE

- This fundamental root key (in win9x it's stored in the hidden file `system.dat`) contains everything pertaining to the current Windows installation.

HKEY_USERS

- This fundamental root key (in win9x it's stored in the hidden file `user.dat`) contains configuration data for every user of the installation.

HKEY_CLASSES_ROOT

- This is a link to HKEY_LOCAL_MACHINE\Software\Classes. It contains data describing things like file associations, OLE document handlers, and COM classes.

HKEY_CURRENT_USER

- This is a link to HKEY_USERS\your_username, i.e., your personal configuration.

## Wine registry data files

In the user's home directory, there is a subdirectory named `.wine`, where Wine will try to save its registry by default. It saves into four files, which are:

`system.reg`

- This file contains HKEY_LOCAL_MACHINE.

`user.reg`

- This file contains HKEY_CURRENT_USER.

`userdef.reg`

- This file contains HKEY_USERS\.Default (i.e. the default user settings).

`wine.userreg`

- Wine saves HKEY_USERS to this file (both current and default user), but does not load from it, unless `userdef.reg` is missing.

All of these files are human-readable text files, so unlike Windows, you can actually use an ordinary text editor on them if you want (make sure you don't have Wine running when modifying them, otherwise your changes will be discarded).

FIXME: global configuration currently not implemented. In addition to these files, Wine can also optionally load from global registry files residing in the same directory as the global `wine.conf` (i.e. `/usr/local/etc` if you compiled from source). These are:

`wine.systemreg`

- Contains HKEY_LOCAL_MACHINE.

`wine.userreg`

- Contains HKEY_USERS.

## System administration

With the above file structure, it is possible for a system administrator to configure the system so that a system Wine installation (and applications) can be shared by all the users, and still let the users all have their own personalized configuration. An administrator can, after having installed Wine and any Windows application software he wants the users to have access to, copy the resulting `system.reg` and `wine.userreg` over to the global registry files (which we assume will reside in `/usr/local/etc` here), with:

      cd ~/.wine
      cp system.reg /usr/local/etc/wine.systemreg
      cp wine.userreg /usr/local/etc/wine.userreg

and perhaps even symlink these back to the administrator's account, to make it easier to install apps system-wide later:

      ln -sf /usr/local/etc/wine.systemreg system.reg
      ln -sf /usr/local/etc/wine.userreg wine.userreg

Note that the `tools/wineinstall` script already does all of this for you, if you install Wine source as root. If you then install Windows applications while logged in as root, all your users will automatically be able to use them. While the application setup will be taken from the global registry, the users' personalized configurations will be saved in their own home directories.

But be careful with what you do with the administrator account - if you do copy or link the administrator's registry to the global registry, any user might be able to read the administrator's preferences, which might not be good if sensitive information (passwords, personal information, etc) is stored there. Only use the administrator account to install software, not for daily work; use an ordinary user account for that.

## The [registry] section

Now let's look at the Wine configuration file options for handling the registry.

GlobalRegistryDir

- Optional. Sets the path to look for the Global Registry.

LoadGlobalRegistryFiles

- Controls whether to try to load the global registry files, if they exist.

LoadHomeRegistryFiles

- Controls whether to try to load the user's registry files (in the `.wine` subdirectory of the user's home directory).

LoadWindowsRegistryFiles

- Controls whether Wine will attempt to load registry data from a real Windows registry in an existing MS Windows installation.

WritetoHomeRegistryFiles

- Controls whether registry data will be written to the user's registry files. (Currently, there is no alternative, so if you turn this off, Wine cannot save the registry on disk at all; after you exit Wine, your changes will be lost.)

SaveOnlyUpdatedKeys

- Controls whether the entire registry is saved to the user's registry files, or only subkeys the user have actually changed. Considering that the user's registry will override any global registry files and Windows registry files, it usually makes sense to only save user-modified subkeys; that way, changes to the rest of the global or Windows registries will still affect the user.

PeriodicSave

- If this option is set to a nonzero value, it specifies that you want the registry to be saved to disk at the given interval. If it is not set, the registry will only be saved to disk when the wineserver terminates.

UseNewFormat

- This option is obsolete. Wine now always uses the new format; support for the old format was removed a while ago.