More Incompatibilities: OpenCV, Display Managers, and Security Changes

lag behind the upstream kernel which made version bumps harder. If you want to use a hardened kernel, please pin it explicitly with a versioned attribute such as `linuxPackages_5_10_hardened`. - The `nomad` package now defaults to a 1.1.x release instead of 1.0.x - If `exfat` is included in `boot.supportedFilesystems` and when using kernel 5.7 or later, the `exfatprogs` user-space utilities are used instead of `exfat`. - The `todoman` package was upgraded from 3.9.0 to 4.0.0. This introduces breaking changes in the [configuration file](https://todoman.readthedocs.io/en/stable/configure.html#configuration-file) format. - The `datadog-agent`, `datadog-integrations-core` and `datadog-process-agent` packages were upgraded from 6.11.2 to 7.30.2, git-2018-09-18 to 7.30.1 and 6.11.1 to 7.30.2, respectively. As a result `services.datadog-agent` has had breaking changes to the configuration file. For details, see the [upstream changelog](https://github.com/DataDog/datadog-agent/blob/main/CHANGELOG.rst). - `opencv2` no longer includes the non-free libraries by default, and consequently `pfstools` no longer includes OpenCV support by default. Both packages now support an `enableUnfree` option to re-enable this functionality. - `services.xserver.displayManager.defaultSession = "plasma5"` does not work anymore, instead use either `"plasma"` for the Plasma X11 session or `"plasmawayland"` for the Plasma Wayland session. - `boot.kernelParams` now only accepts one command line parameter per string. This change is aimed to reduce common mistakes like "param = 12", which would be parsed as 3 parameters. - `nix.daemonNiceLevel` and `nix.daemonIONiceLevel` have been removed in favour of the new options [`nix.daemonCPUSchedPolicy`](options.html#opt-nix.daemonCPUSchedPolicy), [`nix.daemonIOSchedClass`](options.html#opt-nix.daemonIOSchedClass) and [`nix.daemonIOSchedPriority`](options.html#opt-nix.daemonIOSchedPriority). Please refer to the options documentation and the `sched(7)` and `ioprio_set(2)` man pages for guidance on how to use them. - The `coursier` package's binary was renamed from `coursier` to `cs`. Completions which haven't worked for a while should now work with the renamed binary. To keep using `coursier`, you can create a shell alias. - The `services.mosquitto` module has been rewritten to support multiple listeners and per-listener configuration. Module configurations from previous releases will no longer work and must be updated. - The `fluidsynth_1` attribute has been removed, as this legacy version is no longer needed in nixpkgs. The actively maintained 2.x series is available as `fluidsynth` unchanged. - Nextcloud 20 (`pkgs.nextcloud20`) has been dropped because it was EOLed by upstream in 2021-10. - The `virtualisation.pathsInNixDB` option was renamed [`virtualisation.additionalPaths`](options.html#opt-virtualisation.additionalPaths). - The `services.ddclient.password` option was removed, and replaced with `services.ddclient.passwordFile`. - The default GNAT version has been changed: The `gnat` attribute now points to `gnat12` instead of `gnat9`. - `retroArchCores` has been removed. This means that using `nixpkgs.config.retroarch` to customize RetroArch cores is not supported anymore. Instead, use package overrides, for example: `retroarch.override { cores = with libretro; [ citra snes9x ]; };`. Also, `retroarchFull` derivation is available for those who want to have all RetroArch cores available. - The Linux kernel for security reasons now restricts access to BPF syscalls via `BPF_UNPRIV_DEFAULT_OFF=y`. Unprivileged access can be reenabled via the `kernel.unprivileged_bpf_disabled` sysctl knob. - `/usr` will always be included in the initial ramdisk. See the `fileSystems.<name>.neededForBoot` option. If any files exist under `/usr` (which is not typical for NixOS), they will be included in the initial ramdisk, increasing its size to a possibly problematic extent. - `pkgs.haskell-language-server` will now by default be linked dynamically to improve TemplateHaskell compatibility. To mitigate the increased closure size it will now by default only support our current default ghc (at the moment 9.0.2). Add other ghc versions via e.g. `pkgs.haskell-language-server.override { supportedGhcVersions = [ "90" "92" ]; }`.

Further incompatibilities are outlined. `linuxPackages_latest_hardened` was removed, `nomad` defaults to 1.1.x. `exfatprogs` is used for exfat on kernel 5.7+. `todoman` and Datadog packages have config changes. `opencv2` excludes non-free libraries by default, and `services.xserver.displayManager.defaultSession` needs updates. `boot.kernelParams` now accepts one parameter per string. `nix.daemonNiceLevel` and `nix.daemonIONiceLevel` were replaced. The `coursier` binary was renamed to `cs`. `services.mosquitto` was rewritten, requiring config updates. `fluidsynth_1` and Nextcloud 20 were removed. `virtualisation.pathsInNixDB` was renamed. `services.ddclient.password` was replaced. Default GNAT version is `gnat12`. `retroArchCores` was removed, and Linux kernel restricts BPF syscalls. `/usr` is always in initial ramdisk. `pkgs.haskell-language-server` will be linked dynamically.