In addition to numerous new and upgraded packages, this release has the following highlights:

The following new services were added since the last release:

When upgrading from a previous release, please be aware of the following incompatible changes: The minimum version of Nix required to evaluate Nixpkgs is now 2.0. For users of NixOS 18.03 and 19.03, NixOS defaults to Nix 2.0, but supports using Nix 1.11 by setting nix.package = pkgs.nix1;. If this option is set to a Nix 1.11 package, you will need to either unset the option or upgrade it to Nix 2.0. For users of NixOS 17.09, you will first need to upgrade Nix by setting nix.package = pkgs.nixStable2; and run nixos-rebuild switch as the root user. For users of a daemon-less Nix installation on Linux or macOS, you can upgrade Nix by running curl https://nixos.org/nix/install | sh, or prior to doing a channel update, running nix-env -iA nix. If you have already run a channel update and Nix is no longer able to evaluate Nixpkgs, the error message printed should provide adequate directions for upgrading Nix. For users of the Nix daemon on macOS, you can upgrade Nix by running sudo -i sh -c 'nix-channel --update && nix-env -iA nixpkgs.nix'; sudo launchctl stop org.nixos.nix-daemon; sudo launchctl start org.nixos.nix-daemon. Package rabbitmq_server is renamed to rabbitmq-server. The light module no longer uses setuid binaries, but udev rules. As a consequence users of that module have to belong to the video group in order to use the executable (i.e. users.users.yourusername.extraGroups = ["video"];). Buildbot now supports Python 3 and its packages have been moved to pythonPackages. The options services.buildbot-master.package and services.buildbot-worker.package can be used to select the Python 2 or 3 version of the package. Options services.znc.confOptions.networks.name.userName and services.znc.confOptions.networks.name.modulePackages were removed. They were never used for anything and can therefore safely be removed. Package wasm has been renamed proglodyte-wasm. The package wasm will be pointed to ocamlPackages.wasm in 19.09, so make sure to update your configuration if you want to keep proglodyte-wasm OpenSMTPD has been upgraded to version 6.4.0p1. This release makes backwards-incompatible changes to the configuration file format. See man smtpd.conf for more information on the new file format. The versioned postgresql have been renamed to use underscore number seperators. For example, postgresql96 has been renamed to postgresql_9_6.

The services.matomo module gained the option services.matomo.package which determines the used Matomo version. The deprecated truecrypt package has been removed and truecrypt attribute is now an alias for veracrypt. VeraCrypt is backward-compatible with TrueCrypt volumes. Note that cryptsetup also supports loading TrueCrypt volumes.