[Nix-dev] How to run GnuCash (and other GConf applications) on NixOS

[Peter Simons]

GNOME's GConf implements a system-wide registry (like on Windows) that
applications can use to store and retrieve internal configuration data.
That concept is inherently impure, and it's very hard to support on
NixOS. The result is that applications that use GConf -- like GnuCash --
will report tons of error messages at start-up. To remedy those errors,
the GConf daemon must be told the path to the application-specific
${out}/etc/gconf/gconf.xml.defaults/ directory, and the DBus daemon must
be told how to start gconfd whenever an application needs it. To
accomplish that, follow these steps:

 1) Add the following line to ~/.gconf.path:

      xml:readonly:$(HOME)/.nix-profile/etc/gconf/gconf.xml.defaults/

 2) Add the following line to /etc/nixos/configuration.nix:

      services.dbus.packages = [ pkgs.gnome.GConf ];

Now run "nixos-rebuild switch". It may also be necessary to run
"gconftool-2 --shutdown", in case there already is an active gconfd, but
those beasts typically terminate on their own after a few moments of
inactivity.