In addition to numerous new and upgraded packages, this release has the following highlights: You can now pin a specific version of NixOS in your configuration.nix by setting: nixos.path = ./nixpkgs-unstable-2015-12-06/nixos; This will make NixOS re-evaluate your configuration with the modules of the specified NixOS version at the given path. For more details, see When upgrading from a previous release, please be aware of the following incompatible changes: wmiiSnap has been replaced with wmii_hg, but services.xserver.windowManager.wmii.enable has been updated respectively so this only affects you if you have explicitly installed wmiiSnap. wmiimenu is removed, as it has been removed by the developers upstream. Use wimenu from the wmii-hg package. Gitit is no longer automatically added to the module list in NixOS and as such there will not be any manual entries for it. You will need to add an import statement to your NixOS configuration in order to use it, e.g. ]; } ]]> will include the Gitit service configuration options. nginx does not accept flags for enabling and disabling modules anymore. Instead it accepts modules argument, which is a list of modules to be built in. All modules now reside in nginxModules set. Example configuration: