# den - Aspect-oriented context-driven Dendritic Nix configurations. > den and [vic](https://bsky.app/profile/oeiuwq.bsky.social)'s [dendritic libs](https://dendritic.oeiuwq.com) made for you with Love++ and AI--. If you like my work, consider [sponsoring](https://dendritic.oeiuwq.com/sponsor)

# [Documentation](https://den.oeiuwq.com) ### [From Zero To Den](https://den.oeiuwq.com/guides/from-zero-to-den/) ### [From Flake To Den](https://den.oeiuwq.com/guides/from-flake-to-den/) ### [Core Principles](https://den.oeiuwq.com/explanation/core-principles/) ### [Custom Nix Classes](https://den.oeiuwq.com/guides/custom-classes/) ### [Homes Integration](https://den.oeiuwq.com/guides/home-manager/) ### [Batteries](https://den.oeiuwq.com/guides/batteries/) ### [Reference](https://den.oeiuwq.com/reference/ctx/) ### [Tests as Code Examples](https://den.oeiuwq.com/tutorials/ci/) ### [Motivation](https://den.oeiuwq.com/motivation/) ### [Community](https://den.oeiuwq.com/community/)

At its core, Den is a [library](https://den.oeiuwq.com/explanation/library-vs-framework/) built on [flake-aspects](https://github.com/vic/flake-aspects) for activating configuration-aspects via context-transformation pipelines. On top of the library, Den provides a [framework](https://den.oeiuwq.com/explanation/context-pipeline/) for the NixOS/nix-Darwin/Home-Manager Nix domains. Den embraces your Nix choices and does not impose itself. All parts of Den are optional and replaceable. Works with your current setup, with/without flakes, flake-parts or any other Nix module system. ### Templates: [default](https://den.oeiuwq.com/tutorials/default/): +flake-file +flake-parts +home-manager [minimal](https://den.oeiuwq.com/tutorials/minimal): +flakes -flake-parts -home-manager [noflake](https://den.oeiuwq.com/tutorials/noflake): -flakes +npins +lib.evalModules +nix-maid [microvm](https://den.oeiuwq.com/tutorials/microvm): MicroVM runnable-pkg and guests. custom ctx-pipeline. [example](https://den.oeiuwq.com/tutorials/example): cross-platform [ci](https://den.oeiuwq.com/tutorials/ci): Each feature tested as code examples [bogus](https://den.oeiuwq.com/tutorials/bogus): Isolated test for bug reproduction ### Examples: [`vic/vix`](https://github.com/vic/vix): author spends more time in Den itself (-flakes) [`quasigod.xyz`](https://tangled.org/quasigod.xyz/nixconfig): beautiful organization (+flake-parts) [GitHub Search](https://github.com/search?q=den.aspects+language%3ANix&type=code) **❄️ Try it:** ```console # Run virtio MicroVM from templates/microvm nix run github:vic/den?dir=templates/microvm#runnable-microvm ``` ```console # Run qemu VM from templates/example nix run github:vic/den ```

### Testimonials > Den takes the Dendritic pattern to a whole new level, and I cannot imagine going back.\ > — `@adda` - Very early Den adopter after using Dendritic flake-parts and Unify. > I’m super impressed with den so far, I’m excited to try out some new patterns that Unify couldn’t easily do.\ > — `@quasigod` - Author of [Unify](https://codeberg.org/quasigod/unify) dendritic-framework, on adopting Den. > Massive work you did here!\ > — `@drupol` - Author of [“Flipping the Configuration Matrix”](https://not-a-number.io/2025/refactoring-my-infrastructure-as-code-configurations/#flipping-the-configuration-matrix) Dendritic blog post. > Thanks for the awesome library and the support for non-flakes… it’s positively brilliant!. I really hope this gets wider adoption.\ > — `@vczf` - At [`#den-lib:matrix.org`](https://matrix.to/#/#den-lib:matrix.org) channel. > Den is a playground for some very advanced concepts. I’m convinced that some of its ideas will play a role in future Nix areas. In my opinion there are some raw diamonds in Den.\ > — `@Doc-Steve` - Author of [Dendritic Design Guide](https://github.com/Doc-Steve/dendritic-design-with-flake-parts) ## Code example (OS configuration domain) ### Defining hosts, users and homes. ```nix den.hosts.x86_64-linux.lap.users.vic = {}; den.hosts.aarch64-darwin.mac.users.vic = {}; den.homes.aarch64-darwin.vic = {}; ``` ```console $ nixos-rebuild switch --flake .#lap $ darwin-rebuild switch --flake .#mac $ home-manager switch --flake .#vic ``` ### Extensible Schemas for hosts, users and homes. ```nix # extensible base modules for common, typed schemas den.schema.user = { user, lib, ... }: { config.classes = if user.userName == "vic" then [ "hjem" "maid" ] else lib.mkDefault [ "homeManager" ]; options.mainGroup = lib.mkOption { default = user.userName; }; }; ``` ### Dendritic Multi-Platform Hosts ```nix # modules/my-laptop.nix { den, inputs, ... }: { den.aspects.my-laptop = { # re-usable configuration aspects. Den batteries and yours. includes = [ den.provides.hostname den.aspects.work-vpn ]; # regular nixos/darwin modules or any other Nix class nixos = { pkgs, ... }: { imports = [ inputs.disko.nixosModules.disko ]; }; darwin = { pkgs, ... }: { imports = [ inputs.nix-homebrew.darwinModules.nix-homebrew ]; }; # Custom Nix classes. `os` applies to both nixos and darwin. contributed by @Risa-G. # See https://den.oeiuwq.com/guides/custom-classes/#user-contributed-examples os = { pkgs, ... }: { environment.systemPackages = [ pkgs.direnv ]; }; # host can contribute default home environments to all its users. homeManager.programs.vim.enable = true; }; } ``` ### Multiple User Home Environments ```nix # modules/vic.nix { den, ... }: { den.aspects.vic = { # supports multiple home environments, eg: for migrating from homeManager. homeManager = { pkgs, ... }: { }; hjem.files.".envrc".text = "use flake ~/hk/home"; maid.kconfig.settings.kwinrc.Desktops.Number = 3; # user can contribute OS-configurations to any host it lives on darwin.services.karabiner-elements.enable = true; # user class forwards into {nixos/darwin}.users.users. user = { pkgs, ... }: { packages = [ pkgs.helix ]; description = "oeiuwq"; }; includes = [ den.provides.primary-user # re-usable batteries (den.provides.user-shell "fish") # parametric aspects den.aspects.tiling-wm # your own aspects den.aspects.gaming.provides.emulators ]; }; } ``` ### Custom Dendritic Nix Classes [Custom classes](https://den.oeiuwq.com/guides/custom-classes) is how Den implements `homeManager`, `hjem`, `wsl`, `microvm` support. You can use the very same mechanism to create your own classes. ```nix # Example: A class for role-based configuration between users and hosts roleClass = { host, user }: { class, aspect-chain }: den._.forward { each = lib.intersectLists (host.roles or []) (user.roles or []); fromClass = lib.id; intoClass = _: host.class; intoPath = _: [ ]; fromAspect = _: lib.head aspect-chain; }; den.ctx.user.includes = [ roleClass ]; den.hosts.x86_64-linux.igloo = { roles = [ "devops" "gaming" ]; users = { alice.roles = [ "gaming" ]; bob.roles = [ "devops" ]; }; }; den.aspects.alice = { # enabled when both support gaming role gaming = { pkgs, ... }: { programs.steam.enable = true; }; }; den.aspects.bob = { # enabled when both support devops role devops = { pkgs, ... }: { virtualisation.podman.enable = true; }; # not enabled at igloo host (bob missing gaming role on that host) gaming = {}; }; ``` ### Guarded Forwarding Classes Forward guards allow feature-detection without mkIf/mkMerge cluttering. Aspects can simply assign configurations into a class (here `persys`) from any file, without any `mkIf`/`mkMerge` cluttering. The logic for determining if the class takes effect is defined at a single place. > Example inspired by @Doc-Steve ```nix # Aspects use the `persys` class without any conditional. And guard guarantees # settings are applied **only** when impermanence module has been imported. persys = { host }: den._.forward { each = lib.singleton true; fromClass = _: "persys"; intoClass = _: host.class; intoPath = _: [ "environment" "persistance" "/nix/persist/system" ]; fromAspect = _: den.aspects.${host.aspect}; guard = { options, config, ... }: options ? environment.persistance; }; # enable on all hosts den.ctx.host.includes = [ persys ]; # aspects just attach config to custom class den.aspects.my-laptop.persys.hideMounts = true; ``` ### User-defined Extensions to Den Framework. See example [`template/microvm`](https://den.oeiuwq.com/tutorials/microvm) for an example of custom `den.ctx` and `den.schema` extensions for supporting Declarative [MicroVM](https://microvm-nix.github.io/microvm.nix/declarative.html) guests with automatic host-shared `/nix/store`. ```nix den.hosts.x86_64-linux.guest = {}; den.hosts.x86_64-linux.host = { microvm.guests = [ den.hosts.x86_64-linux.guest ]; }; den.aspects.guest = { # propagated into host.nixos.microvm.vms.; microvm.autostart = true; # guest supports all Den features. includes = [ den.provides.hostname ]; # As MicroVM guest propagated into host.nixos.microvm.vms..config; nixos = { pkgs, ... }: { environment.systemPackages = [ pkgs.hello ]; }; }; ```