In addition to numerous new and upgraded packages, this release has the following highlights: The Haskell packages infrastructure has been re-designed from the ground up. NixOS now distributes the latest version of every single package registered on Hackage, i.e. well over 8000 Haskell packages. Further information and usage instructions for the improved infrastructure are available at https://nixos.org/wiki/Haskell. Users migrating from an earlier release will find also find helpful information below, in the list of backwards-incompatible changes. Users running an SSH server who worry about the quality of their /etc/ssh/moduli file with respect to the vulnerabilities discovered in the Diffie-Hellman key exchange can now replace OpenSSH's default version with one they generated themselves using the new services.openssh.moduliFile option. When upgrading from a previous release, please be aware of the following incompatible changes: sshd no longer supports DSA and ECDSA host keys by default. If you have existing systems with such host keys and want to continue to use them, please set system.stateVersion = "14.12"; (The new option system.stateVersion ensures that certain configuration changes that could break existing systems (such as the sshd host key setting) will maintain compatibility with the specified NixOS release.) cron is no longer enabled by default, unless you have a non-empty services.cron.systemCronJobs. To force cron to be enabled, set services.cron.enable = true. Nix now requires binary caches to be cryptographically signed. If you have unsigned binary caches that you want to continue to use, you should set nix.requireSignedBinaryCaches = false. Steam now doesn't need root rights to work. Instead of using *-steam-chrootenv, you should now just run steam. steamChrootEnv package was renamed to steam, and old steam package -- to steamOriginal. CMPlayer has been renamed to bomi upstream. Package cmplayer was accordingly renamed to bomi Atom Shell has been renamed to Electron upstream. Package atom-shell was accordingly renamed to electron Elm is not released on Hackage anymore. You should now use elmPackages.elm which contains the latest Elm platform. The CUPS printing service has been updated to version 2.0.2. Furthermore its systemd service has been renamed to cups.service. Local printers are no longer shared or advertised by default. This behavior can be changed by enabling services.printing.defaultShared or services.printing.browsing respectively. The VirtualBox host and guest options have been moved/renamed more consistently and less confusing to be now found in virtualisation.virtualbox.host.* instead of services.virtualboxHost.* and virtualisation.virtualbox.guest.* instead of services.virtualboxGuest.*. Haskell packages can no longer be found by name, i.e. the commands nix-env -qa cabal-install and nix-env -i ghc will fail, even though we do ship both cabal-install and ghc. The reason for this inconvenience is the sheer size of the Haskell package set: name-based lookups such as these would become much slower than they are today if we'd add the entire Hackage database into the top level attribute set. Instead, the list of Haskell packages can be displayed by nix-env -f "<nixpkgs>" -qaP -A haskellPackages and packages can be installed with: nix-env -f "<nixpkgs>" -iA haskellPackages.cabal-install Previous versions of NixOS came with a feature called ghc-wrapper, a small wrapper script that allows GHC to transparently pick up on libraries installed in the user's profile. This feature has been deprecated; ghc-wrapper was removed from the distribution. The proper way to register Haskell libraries with the compiler now is the haskellPackages.ghcWithPackages function. https://nixos.org/wiki/Haskell provides much information about this subject. All Haskell builds that have been generated with version 1.x of the cabal2nix utility are now invalid and need to be re-generated with a current version of cabal2nix to function. The most recent version of this tool can be installed by running nix-env -i cabal2nix. The haskellPackages set in Nixpkgs used to have a function attribute called extension that users could override in their ~/.nixpkgs/config.nix files to configure additional attributes, etc. That function still exists, but it's now called overrides. The OpenBLAS library has been updated to version 0.2.14. Support for the x86_64-darwin platform was added. Dynamic architecture detection was enabled; OpenBLAS now selects microarchitecture-optimized routines at runtime, so optimal performance is achieved without the need to rebuild OpenBLAS locally. OpenBLAS has replaced ATLAS in most packages which use an optimized BLAS or LAPACK implementation. The phpfpm is now using the default PHP version (pkgs.php) instead of PHP 5.4 (pkgs.php54). The locate service no longer indexes the Nix store by default, preventing packages with potentially numerous versions from cluttering the output. Indexing the store can be activated by setting services.locate.includeStore = true. The Nix expression search path (NIX_PATH) no longer contains /etc/nixos/nixpkgs by default. You can override NIX_PATH by setting nix.nixPath. The following new services were added since the last release: brltty marathon tvheadend Other notable improvements: The nixos and nixpkgs channels were unified, so one can use nix-env -iA nixos.bash instead of nix-env -iA nixos.pkgs.bash. See the commit for details.