In addition to numerous new and upgraded packages, this release has the following highlights: Nixpkgs is now extensible through overlays. See the Nixpkgs manual for more information. The following new services were added since the last release: When upgrading from a previous release, please be aware of the following incompatible changes: Cross compilation has been rewritten. See the nixpkgs manual for details. The most obvious breaking change is that derivations absent a .nativeDrv or .crossDrv are now cross by default, not native. stdenv.overrides is now expected to take self and super arguments. See lib.trivial.extends for what those parameters represent. ansible now defaults to ansible version 2 as version 1 has been removed due to a serious vulnerability unpatched by upstream. gnome alias has been removed along with gtk, gtkmm and several others. Now you need to use versioned attributes, like gnome3. The attribute name of the Radicale daemon has been changed from pythonPackages.radicale to radicale. The Yama LSM is now enabled by default in the kernel, which prevents ptracing non-child processes. This means you will not be able to attach gdb to an existing process, but will need to start that process from gdb (so it is a child). The stripHash bash function in stdenv changed according to its documentation; it now outputs the stripped name to stdout instead of putting it in the variable strippedName. PHP now scans for extra configuration .ini files in /etc/php.d instead of /etc. This prevents accidentally loading non-PHP .ini files that may be in /etc. Parsoid service now uses YAML configuration format. service.parsoid.interwikis is now called service.parsoid.wikis and is a list of either API URLs or attribute sets as specified in parsoid's documentation. Ntpd was replaced by systemd-timesyncd as the default service to synchronize system time with a remote NTP server. The old behavior can be restored by setting services.ntp.enable to true. Upstream time servers for all NTP implementations are now configured using networking.timeServers. overridePackages function no longer exists. It is replaced by overlays. For example, the following code: let pkgs = import <nixpkgs> {}; in pkgs.overridePackages (self: super: ...) should be replaced by: let pkgs = import <nixpkgs> {}; in import pkgs.path { overlays = [(self: super: ...)] } Autoloading connection tracking helpers is now disabled by default. This default was also changed in the Linux kernel and is considered insecure if not configured properly in your firewall. If you need connection tracking helpers (i.e. for active FTP) please enable networking.firewall.autoLoadConntrackHelpers and tune networking.firewall.connectionTrackingModules to suit your needs. Other notable improvements: Module type system have a new extensible option types feature that allow to extend certain types, such as enum, through multiple option declarations of the same option across multiple modules.