NixOS 19.03: Notable Changes - Matomo, composableDerivation, TrueCrypt, Kubernetes DNS, and More

## Other Notable Changes {#sec-release-19.03-notable-changes} - The `services.matomo` module gained the option `services.matomo.package` which determines the used Matomo version. The Matomo module now also comes with the systemd service `matomo-archive-processing.service` and a timer that automatically triggers archive processing every hour. This means that you can safely [ disable browser triggers for Matomo archiving ](https://matomo.org/docs/setup-auto-archiving/#disable-browser-triggers-for-matomo-archiving-and-limit-matomo-reports-to-updating-every-hour) at `Administration > System > General Settings`. Additionally, you can enable to [ delete old visitor logs ](https://matomo.org/docs/privacy/#step-2-delete-old-visitors-logs) at `Administration > System > Privacy`, but make sure that you run `systemctl start matomo-archive-processing.service` at least once without errors if you have already collected data before, so that the reports get archived before the source data gets deleted. - `composableDerivation` along with supporting library functions has been removed. - 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. - The Kubernetes DNS addons, kube-dns, has been replaced with CoreDNS. This change is made in accordance with Kubernetes making CoreDNS the official default starting from [Kubernetes v1.11](https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG-1.11.md#sig-cluster-lifecycle). Please beware that upgrading DNS-addon on existing clusters might induce minor downtime while the DNS-addon terminates and re-initializes. Also note that the DNS-service now runs with 2 pod replicas by default. The desired number of replicas can be configured using: `services.kubernetes.addons.dns.replicas`. - The quassel-webserver package and module was removed from nixpkgs due to the lack of maintainers. - The manual gained a [ new chapter on self-hosting `matrix-synapse` and `riot-web` ](#module-services-matrix), the most prevalent server and client implementations for the [Matrix](https://matrix.org/) federated communication network. - The astah-community package was removed from nixpkgs due to it being discontinued and the downloads not being available anymore. - The httpd service now saves log files with a .log file extension by default for easier integration with the logrotate service. - The owncloud server packages and httpd subservice module were removed from nixpkgs due to the lack of maintainers. - It is possible now to uze ZRAM devices as general purpose ephemeral block devices, not only as swap. Using more than 1 device as ZRAM swap is no longer recommended, but is still possible by setting `zramSwap.swapDevices` explicitly. ZRAM algorithm can be changed now. Changes to ZRAM algorithm are applied during `nixos-rebuild switch`, so make sure you have enough swap space on disk to survive ZRAM device rebuild. Alternatively, use `nixos-rebuild boot; reboot`. - Flat volumes are now disabled by default in `hardware.pulseaudio`. This has been done to prevent applications, which are unaware of this feature, setting their volumes to 100% on startup causing harm to your audio hardware and potentially your ears.

This section highlights notable changes in NixOS 19.03, including updates to the Matomo module with a new package option and systemd service for archive processing. It also covers the removal of `composableDerivation` and the deprecated `truecrypt` package (now aliased to VeraCrypt). The Kubernetes DNS addon has been replaced with CoreDNS. Additionally, the quassel-webserver package and module were removed due to lack of maintainers. A new manual chapter on self-hosting `matrix-synapse` and `riot-web` was added. Other changes include the removal of the astah-community package, log file extension changes for httpd, removal of owncloud server packages and the httpd subservice module, updates to ZRAM device usage, and the disabling of flat volumes by default in pulseaudio.