87 changed files with 1669 additions and 2422 deletions
--- a/.envrc
+++ b/.envrc
@ -1,6 +1,4 @@
-HOST_XDG_DATA_DIRS="${XDG_DATA_DIRS:-}"
 eval "$(lorri direnv)"
-export XDG_DATA_DIRS="${XDG_DATA_DIRS}:${HOST_XDG_DATA_DIRS}"

 # Use system PKI
 unset SSL_CERT_FILE
--- a/.gitignore
+++ b/.gitignore
@ -5,5 +5,3 @@ dist/
 dist-newstyle/
 cabal.project.local

-*.swp
-
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@ -1,100 +1,9 @@
 # Revision history for Arion

-## 0.2.1.0 -- 2023-07-26
+## Unreleased

-### Added
-
-* `service.networks` now supports attribute set values with various options, thanks to @pedorich-n.
-* `docker-compose.volumes` can now be specified in multiple modules, thanks to @qaifshaikh.
-* `image.fakeRootCommands` for making modifications to the image that aren't "add a link farm".
-
-### Fixed
-
-* Regular maintenance fixes, including one by olebedev
-
-
-## 0.2.0.0 -- 2022-12-02
-
-### BREAKING
-
-* The `project.name` option is now mandatory for projects that aren't deployed with the NixOS module.
-
-* The NixOS module now sets the default network name to the project name (commonly referred to as `<name>` in the option path).
-  If this is not desired, for instance if you need the projects to be on the same network, set `networks.default.name` in each of them.
-
-* The NixOS module now sets the default project name. You can still set your own value with the `project.name` option.
-  If you did not set one, docker compose heuristically determined the name to be `store`, so you may want to set `project.name = "store"` or prepare to rename the network manually.
-
-### Removed
-
- - NixOS 20.09 support. Its docker-compose does not support the
-   `networks.<name>.name` option, which is important in later versions.
-   A newer, bundled docker compose may work there, but for now the decision
-   is to drop this legacy version.
-
-### Changed
-
-* Healthcheck-based dependencies in `service.depends_on`.
-
-### Added
-
-* Support `service.healthcheck` for defining custom healthchecks.
-* Arion now declares a `networks.default` by default, with `name` set to
-  `project.name`. This improves compatibility with container runtimes by
-  copying pre-existing behavior. Most users will want to keep using this
-  behavior, but it can be disabled with `enableDefaultNetwork`.
-
-## 0.1.3.0 -- 2020-05-03
-
-### Changed
-
-* `useHostStore` now uses an image derived from the `image.*` options. You may
-  need to enable `enableRecommendedContents` because with this change, files
-  like `/bin/sh` aren't added by default anymore.
-
-* Drop obsolete NixOS 19.03, 19.09 and 20.03 from CI.
-
-### Added
-
-* NixOS-based containers can now run on Podman when it is configured to provide a docker socket. See the [installation docs](https://docs.hercules-ci.com/arion/#_nixos).
-
-* Support `service.dns`, for overriding the DNS servers used by containers.
-
-* Support `service.labels`, which is useful for autodiscovery among other things.
-
-* Add a tested example for Traefik with label-based routing.
-
-* Add a `flake.nix` and an experimental flake example
-
-* Add a warning when systemd `DynamicUser` is used but not available to the
-  container.
-
-* CI with NixOS 21.05
-
-## 0.1.2.0 -- 2020-03-05
-
-* Support use of prebuilt `docker-compose.yaml`.
-  Separates build and execution without duplicating evaluation.
-
-* Avoid storing tarballs (wasting store space) by using
-  `dockerTools.streamLayeredImage` if available.
-
-* Project name is now configurable via the `project.name` option
-
-* Support --no-ansi, --compatibility, --log-level options
-
-## 0.1.1.1 -- 2020-03-20
-
-* Fix ambiguous import of `lines`
-* Improve base version constraint
-* Fix warnings
-
-## 0.1.1.0 -- 2020-03-19
-
-* Support Nixpkgs 20.03
-* Fixes for macOS
+<!-- TODO: use better template -->

 ## 0.1.0.0 -- 2019-10-04

 * First released version. Released on an unsuspecting world.
-
--- a/arion-compose.cabal
+++ b/arion-compose.cabal
@ -1,7 +1,7 @@
 cabal-version:       2.4

 name:                arion-compose
-version: 0.2.1.0
+version: 0.1.0.0
 synopsis:            Run docker-compose with help from Nix/NixOS
 description:         Arion is a tool for building and running applications that consist of multiple docker containers using NixOS modules. It has special support for docker images that are built with Nix, for a smooth development experience and improved performance.
 homepage:            https://github.com/hercules-ci/arion#readme
@ -17,7 +17,6 @@ extra-source-files:  CHANGELOG.md, README.asciidoc,
                     src/haskell/testdata/**/*.json
 data-files:          nix/*.nix
                   , nix/modules/composition/*.nix
-                   , nix/modules/networks/*.nix
                   , nix/modules/nixos/*.nix
                   , nix/modules/service/*.nix
                   , nix/modules/lib/*.nix
@ -25,13 +24,9 @@ data-files:          nix/*.nix
 -- all data is verbatim from some sources
 data-dir:            src

-source-repository head
-  type: git
-  location: https://github.com/hercules-ci/arion
-
 common common
-  build-depends:     base >=4.12.0.0 && <4.99
-                   , aeson >=2
+  build-depends:     base ^>=4.12.0.0
+                   , aeson
                   , aeson-pretty
                   , async
                   , bytestring
@ -41,7 +36,7 @@ common common
                   , process
                   , temporary
                   , text
-                   , protolude >= 0.2
+                   , protolude
                   , unix
  ghc-options:     -Wall

@ -54,7 +49,6 @@ library
  exposed-modules:     Arion.Nix
                       Arion.Aeson
                       Arion.DockerCompose
-                       Arion.ExtendedInfo
                       Arion.Images
                       Arion.Services
  other-modules:       Paths_arion_compose
--- a/bors.toml
+++ b/bors.toml
@ -1,5 +1,5 @@
 status = [
-  "ci/hercules/onPush/default",
+  "ci/hercules/derivations",
  "ci/hercules/evaluation",
 ]
 delete_merged_branches = true
--- a/default.nix
+++ b/default.nix
@ -1,11 +1,6 @@
-let flake = import ./nix/compat.nix;
-in
-{ pkgs ? import flake.inputs.nixpkgs { }
+{ pkgs ? import ./nix {}
 , haskellPackages ? pkgs.haskellPackages
 }:
-let
-  pkgsWithArion = pkgs.extend flake.overlays.default;
-in
 {
-  inherit (pkgsWithArion) arion;
+  arion = import ./nix/arion.nix { inherit pkgs haskellPackages; };
 }
--- a/docs/README.md
+++ b/docs/README.md
@ -1,4 +0,0 @@
-
-# Documentation
-
-Please refer to the [**rendered documentation**](https://docs.hercules-ci.com/arion), which includes the [**options.**](https://docs.hercules-ci.com/arion/options/)
--- a/docs/antora.yml
+++ b/docs/antora.yml
@ -4,4 +4,3 @@ version: 'master'
 nav:
 - modules/ROOT/nav.adoc
 - modules/reference/nav.adoc
-nix: true
--- a/docs/flake-module.nix
+++ b/docs/flake-module.nix
@ -1,31 +0,0 @@
-{
-  perSystem = { config, pkgs, lib, ... }: {
-    packages.generated-option-doc-arion =
-      # TODO: use the render pipeline in flake-parts,
-      #       which has support for things like {options}`foo`.
-      let
-        eval = lib.evalModules {
-          modules = import ../src/nix/modules.nix;
-        };
-      in
-      (pkgs.nixosOptionsDoc
-        {
-          options = eval.options;
-        }).optionsCommonMark;
-
-    packages.generated-antora-files =
-      pkgs.runCommand "generated-antora-files"
-        {
-          nativeBuildInputs = [ pkgs.pandoc ];
-          doc_arion = config.packages.generated-option-doc-arion;
-        }
-        # TODO: use the render pipeline in flake-parts,
-        #       which has support for things like {options}`foo`.
-        ''
-          mkdir -p $out/modules/ROOT/partials
-          pandoc --from=markdown --to=asciidoc \
-            < $doc_arion \
-            > $out/modules/ROOT/partials/arion-options.adoc
-        '';
-  };
-}
--- a/docs/modules/ROOT/examples/full-nixos/arion-compose.nix
+++ b/docs/modules/ROOT/examples/full-nixos/arion-compose.nix
@ -1 +0,0 @@
-../../../../../examples/full-nixos/arion-compose.nix
--- a/docs/modules/ROOT/examples/minimal/arion-compose.nix
+++ b/docs/modules/ROOT/examples/minimal/arion-compose.nix
@ -1 +0,0 @@
-../../../../../examples/minimal/arion-compose.nix
--- a/docs/modules/ROOT/examples/nixos-unit/arion-compose.nix
+++ b/docs/modules/ROOT/examples/nixos-unit/arion-compose.nix
@ -1 +0,0 @@
-../../../../../examples/nixos-unit/arion-compose.nix
--- a/docs/modules/ROOT/nav.adoc
+++ b/docs/modules/ROOT/nav.adoc
@ -1,3 +1,2 @@
 * xref:index.adoc[Getting Started]
 * xref:options.adoc[Arion Options]
-* xref:deployment.adoc[Deployment]
--- a/docs/modules/ROOT/pages/deployment.adoc
+++ b/docs/modules/ROOT/pages/deployment.adoc
@ -1,71 +0,0 @@
-= Deployment with Arion
-
-Arion projects can be deployed in Nix-like or Docker-like ways.
-
-== Docker images
-
-When you disable `useHostStore`, arion will build images, which can be deployed
-to any Docker host, including non-NixOS hosts.
-
-=== Remote Docker socket
-
-NOTE: Access to a Docker socket is equivalent to root access on the host.
-
-Docker supports authentication via TLS client certificates.
-
-The xref:hercules-ci-effects:ROOT:reference/nix-functions/runArion.adoc[runArion Effect] uses this technique.
-
-Because this technique works with a single Docker host, it does not need a registry.
-
-=== Upload to registry
-
-You can either use `arion push` or write custom push logic using the `arion cat`
-command, the `eval` function on the `arion` package, or the `lib.eval` function
-on the flake to retrieve the images defined in a project.
-
-== NixOS module
-
-Arion projects can be deployed as part of a NixOS configuration. This ties the
-project revision to the system configuration revision, which can be good or bad
-thing, depending on your deployment strategy. At a low level, a benefit is that
-no store paths need to be copied locally and remote NixOS deployments can use
-Nix's copy-closure algorithm for efficient transfers, and transparent binary
-caches rather than an inherently stateful Docker registry solution.
-
-Extend your NixOS configuration by adding the configuration elements to an
-existing configuration. You could create a new module file for it, if your
-choice of `imports` allows it.
-
-NOTE: This deployment method does NOT use an `arion-pkgs.nix` file, but reuses
-      the host `pkgs`.
-
-```nix
-{
-  imports = [
-    # Pick one of:
-    #  - niv
-    ((import ./nix/sources.nix).arion + "/nixos-module.nix")
-    #  - or flakes (where arion is a flake input)
-    arion.nixosModules.arion
-    #  - or other: copy commit hash of arion and replace HASH in:
-    (builtins.fetchTarball "https://github.com/hercules-ci/arion/archive/HASH.tar.gz") + "/nixos-module.nix")
-  ];
-
-  virtualisation.arion = {
-    backend = "podman-socket"; # or "docker"
-    projects.example = {
-      serviceName = "example"; # optional systemd service name, defaults to arion-example in this case
-      settings = {
-        # Specify you project here, or import it from a file.
-        # NOTE: This does NOT use ./arion-pkgs.nix, but defaults to NixOS' pkgs.
-        imports = [ ./arion-compose.nix ];
-      };
-    };
-  };
-}
-```
-
-See also:
-
- - xref:hercules-ci-effects:ROOT:reference/nix-functions/runNixOS.adoc[runNixOS Effect]
- - xref:hercules-ci-effects:ROOT:reference/nix-functions/runNixOps2.adoc[runNixOps2 Effect]
--- a/docs/modules/ROOT/pages/index.adoc
+++ b/docs/modules/ROOT/pages/index.adoc
@ -39,13 +39,6 @@ Arion allows to compose containers with different granularity:
  * <<NixOS: run full OS>>
  * <<Docker image from DockerHub>>

-Full NixOS is supported on
-
- * docker-compose + podman with docker socket (NixOS >= 21.05)
- * docker-compose + docker, before cgroupsv2 (NixOS < 21.05)
-
-`podman-compose` support is currently WIP on a separate branch.
-
 == Installation

 === Nix
@ -59,24 +52,10 @@ $ nix-env -iA arion -f https://github.com/hercules-ci/arion/tarball/master
 Add this module to your NixOS configuration:

 ```nix
-{ pkgs, ... }: {
-  environment.systemPackages = [
-    pkgs.arion
-
-     # Do install the docker CLI to talk to podman.
-     # Not needed when virtualisation.docker.enable = true;
-    pkgs.docker-client
-  ];
-
-  # Arion works with Docker, but for NixOS-based containers, you need Podman
-  # since NixOS 21.05.
-  virtualisation.docker.enable = false;
-  virtualisation.podman.enable = true;
-  virtualisation.podman.dockerSocket.enable = true;
-  virtualisation.podman.defaultNetwork.dnsname.enable = true;
-
-  # Use your username instead of `myuser`
-  users.extraUsers.myuser.extraGroups = ["podman"];
+{ ... }: {
+  environment.systemPackages = [ (import (builtins.fetchTarball https://github.com/hercules-ci/arion/tarball/master) {}).arion ];
+  virtualisation.docker.enable = true;
+  users.extraUsers.myuser.extraGroups = ["docker"];
 }
 ```

@ -113,16 +92,14 @@ Describe containers using NixOS-style modules. There are a few options:

 ==== Minimal: Plain command using nixpkgs

-`examples/minimal/arion-compose.nix`
-[,nix]
----
+`examples/minimal/arion-compose.nix`:
+
+```nix
 { pkgs, ... }:
 {
-  project.name = "webapp";
-  services = {
+  config.services = {

    webserver = {
-      image.enableRecommendedContents = true;
      service.useHostStore = true;
      service.command = [ "sh" "-c" ''
                  cd "$$WEB_ROOT"
@ -132,36 +109,62 @@ Describe containers using NixOS-style modules. There are a few options:
        "8000:8000" # host:container
      ];
      service.environment.WEB_ROOT = "${pkgs.nix.doc}/share/doc/nix/manual";
-      service.stop_signal = "SIGINT";
    };
  };
 }
----

-==== NixOS: run full OS

-`examples/full-nixos/arion-compose.nix`:
+```
+
+==== NixOS: run only one systemd service
+
+`examples/nixos-unit/arion-compose.nix`:
+
+```nix

-[,nix]
----
 {
-  project.name = "full-nixos";
-  services.webserver = { pkgs, lib, ... }: {
-    nixos.useSystemd = true;
-    nixos.configuration.boot.tmp.useTmpfs = true;
-    nixos.configuration.services.nginx.enable = true;
-    nixos.configuration.services.nginx.virtualHosts.localhost.root = "${pkgs.nix.doc}/share/doc/nix/manual";
-    nixos.configuration.services.nscd.enable = false;
-    nixos.configuration.system.nssModules = lib.mkForce [];
-    nixos.configuration.systemd.services.nginx.serviceConfig.AmbientCapabilities = 
-      lib.mkForce [ "CAP_NET_BIND_SERVICE" ];
+  services.webserver = { config, pkgs, ... }: {
+
+    nixos.configuration = {config, pkgs, ...}: {
+      boot.isContainer = true;
+      services.nginx.enable = true;
+      services.nginx.virtualHosts.localhost.root = "${pkgs.nix.doc}/share/doc/nix/manual";
+      system.build.run-nginx = pkgs.writeScript "run-nginx" ''
+        #!${pkgs.bash}/bin/bash
+        PATH='${config.systemd.services.nginx.environment.PATH}'
+        echo nginx:x:${toString config.users.users.nginx.uid}:${toString config.users.groups.nginx.gid}:nginx web server user:/var/empty:/bin/sh >>/etc/passwd
+        echo nginx:x:${toString config.users.groups.nginx.gid}:nginx >>/etc/group
+        ${config.systemd.services.nginx.runner}
+      '';
+    };
+    service.command = [ config.nixos.build.run-nginx ];
    service.useHostStore = true;
    service.ports = [
      "8000:80" # host:container
    ];
  };
 }
----
+
+```
+
+==== NixOS: run full OS
+
+`examples/full-nixos/arion-compose.nix`:
+
+```nix
+{
+  services.webserver = { pkgs, ... }: {
+    nixos.useSystemd = true;
+    nixos.configuration.boot.tmpOnTmpfs = true;
+    nixos.configuration.services.nginx.enable = true;
+    nixos.configuration.services.nginx.virtualHosts.localhost.root = "${pkgs.nix.doc}/share/doc/nix/manual";
+    service.useHostStore = true;
+    service.ports = [
+      "8000:80" # host:container
+    ];
+  };
+}
+```

 ==== Docker image from DockerHub

@ -175,11 +178,6 @@ Describe containers using NixOS-style modules. There are a few options:
 }
 ```

-==== NixOS: run only one systemd service
-
-Running individual units from NixOS is possible using an experimental script.
-See `examples/nixos-unit/arion-compose.nix`.
-
 === Run

 Start containers and watch their logs:
@ -191,47 +189,15 @@ $ arion logs -f

 You can go to `examples/*/` and run these commands to give it a quick try.

-=== Inspect the config
+== A full featured Nix command example

-While developing an arion project, you can make use of `arion repl`, which launches
-a `nix repl` on the project configuration.
+To see how Arion can be used in a project, have a look at
+https://github.com/nix-community/todomvc-nix/tree/master/deploy/arion[todomvc-nix].

-```
-$ arion repl
-Launching a repl for you. To get started:
-
-To see deployment-wide configuration
-  type config. and use tab completion
-To bring the top-level Nixpkgs attributes into scope
-  type :a (config._module.args.pkgs) // { inherit config; }
-
-Welcome to Nix. Type :? for help.
-
-Loading '../../src/nix/eval-composition.nix'...
-Added 5 variables.
-
-nix-repl> config.services.webserver.service.command
-[ "sh" "-c" "cd \"$$WEB_ROOT\"\n/nix/store/66fbv9mmx1j4hrn9y06kcp73c3yb196r-python3-3.8.9/bin/python -m http.server\n" ]
-
-nix-repl>
-
-```
-
-== Build with Nix
-
-You can build a project with `nix-build` using an expression like
-
-```nix
-arion.build { modules = [ ./arion-compose.nix ]; pkgs = import ./arion-pkgs.nix; }
-```
-
-If you deploy with xref:hercules-ci-effects:ROOT:reference/nix-functions/runArion.adoc[runArion],
-and your `pkgs` variable is equivalent to `import ./arion-pkgs.nix`, you can use:
-
-```nix
-let
-  deployment = pkgs.effects.runArion { /* ... */ });
-in deployment.prebuilt
+```bash
+$ git clone https://github.com/nix-community/todomvc-nix
+$ cd todomvc-nix/deploy/arion
+$ arion up
 ```

 == Project Status
@ -241,10 +207,10 @@ development environments while working on
 https://www.hercules-ci.com[Hercules CI]. (It was also born out of
 ancient Greek deities disguised as horses. More on that later.)

-Arion can be used for simple single host deployments, using Docker's TLS
-client verification, or https://search.nixos.org/options?channel=unstable&show=virtualisation.podman.networkSocket.enable&query=virtualisation.podman[`virtualisation.podman.networkSocket` options].
-Remote deployments do not support `useHostStore`, although an SSH-based deployment method could support this.
-Docker Swarm is not currently supported.
+If you do want to use Arion for production environments, you’ll probably
+want to either build normal container images or manage garbage
+collection roots if you control the deployment host. Neither scenario is
+made easier by arion at this time.

 Arion has run successfully on Linux distributions other than NixOS, but we only perform CI for Arion on NixOS.

@ -265,7 +231,7 @@ configuration that makes the Docker Compose file do the things it needs
 to do.

 One of the more interesting built-in modules is the
-https://github.com/hercules-ci/arion/blob/master/src/nix/modules/service/host-store.nix[host-store.nix module] which
+link:src/nix/modules/service/host-store.nix[host-store.nix module] which
 performs the bind mounts to make the host Nix store available in the
 container.

@ -275,23 +241,21 @@ container.

 Nope, it’s just Nix and Docker Compose under the hood.

-It does xref:hercules-ci-effects:ROOT:reference/nix-functions/runArion.adoc[integrate] nicely though.
-
 === What about garbage collection?

 Arion removes the need for garbage collecting docker images, delegating
-this task to Nix when using `service.useHostStore`.
+this task to Nix.

-Arion creates a garbage collection root that it cleans up after completing
-the command. This means that `arion up -d` should not be used with `useHostStore`
-in production. Instead, disable `useHostStore`, which will use `dockerTools` to
-generate images that can be used in production.
+Arion creates a garbage collection root and cleans it up after
+completing the command. This means that `arion up` without `-d` is safe
+with respect to garbage collection. A deployment that is more serious
+than local development must leave a GC root on the deployment host. This
+use case is not supported as of now.

 === Why is my container not running latest code?

-Rebuild the image using `arion up -d --always-recreate-deps <name>` or simply `arion up -d`.
-
-Like `docker-compose restart`, `arion restart` does not update the image before starting.
+Restart it with `arion restart <name>` or if you've changed the image rebuild
+them using `arion up -d --always-recreate-deps <name>`.

 === What is messing with my environment variables?

@ -302,11 +266,11 @@ reference a script from `pkgs.writeScript` or escape the dollar sign as

 === Why name it ``Arion``?

-Arion comes from Greek mythology. Poseidon, the god of Docker -- I mean the seas --
+Arion comes from Greek mythology. Poseidon, the god of ~Docker~ the seas
 had his eye on Demeter. Demeter tried to trick him by disguising as a
 horse, but Poseidon saw through the deception and they had Arion.

 So Arion is a super fast divine horse; the result of some weird mixing.
 Also it talks.

-(And we felt morally obliged to name our stuff after Greek mythology)
+(And we feel morally obliged to name our stuff after Greek mythology)
--- a/docs/modules/ROOT/pages/options.adoc
+++ b/docs/modules/ROOT/pages/options.adoc
@ -1,3 +1 @@
-# Arion Options
-
-include::partial$arion-options.adoc[]
+include::partial$NixOSOptions.adoc[]
--- a/docs/modules/ROOT/partials/NixOSOptions.adoc
+++ b/docs/modules/ROOT/partials/NixOSOptions.adoc
@ -0,0 +1,941 @@
+= Arion options
+
+== docker-compose.extended
+
+Attribute set that will be turned into the x-arion section of the docker-compose.yaml file.
+
+[discrete]
+=== details
+
+Type:: attribute set
+No Default:: {blank}
+
+No Example:: {blank}
+
+== docker-compose.raw
+
+Attribute set that will be turned into the docker-compose.yaml file, using Nix's toJSON builtin.
+
+[discrete]
+=== details
+
+Type:: attribute set
+No Default:: {blank}
+
+No Example:: {blank}
+
+== host.nixStorePrefix
+
+Prefixes store paths on the host, allowing the Nix store to be
+stored at an alternate location without altering the format of
+store paths.
+
+For example: instead of mounting the host's /nix/store as the
+container's /nix/store, this will mount /mnt/foo/nix/store
+as the container's /nix/store.
+
+
+[discrete]
+=== details
+
+Type:: string
+Default::
+
+----
+""
+----
+
+
+Example::
+
+----
+"/mnt/foo"
+----
+
+
+== host.uid
+
+The numeric user id (UID) of the user running arion.
+
+This lets you to write modules that interact with the host
+user's files, which is helpful for local development, but not
+intended for production-like deployment scenarios.
+
+
+[discrete]
+=== details
+
+Type:: signed integer
+No Default:: {blank}
+
+No Example:: {blank}
+
+== out.dockerComposeYaml
+
+A derivation that produces a docker-compose.yaml file for this composition.
+
+[discrete]
+=== details
+
+Type:: package
+No Default:: {blank}
+Read Only:: {blank}
+No Example:: {blank}
+
+== out.dockerComposeYamlAttrs
+
+The text of out.dockerComposeYaml.
+
+[discrete]
+=== details
+
+Type:: attribute set of unspecifieds
+No Default:: {blank}
+Read Only:: {blank}
+No Example:: {blank}
+
+== out.dockerComposeYamlText
+
+The text of out.dockerComposeYaml.
+
+[discrete]
+=== details
+
+Type:: string
+No Default:: {blank}
+Read Only:: {blank}
+No Example:: {blank}
+
+== services
+
+An attribute set of service configurations. A service specifies how to run an image as a container.
+
+[discrete]
+=== details
+
+Type:: attribute set of submodules
+No Default:: {blank}
+
+No Example:: {blank}
+
+== services.<name>.composition
+
+The composition configuration.
+
+
+[discrete]
+=== details
+
+Type:: attribute set
+No Default:: {blank}
+Read Only:: {blank}
+No Example:: {blank}
+
+== services.<name>.host
+
+The composition-level host option values.
+
+
+[discrete]
+=== details
+
+Type:: attribute set
+No Default:: {blank}
+Read Only:: {blank}
+No Example:: {blank}
+
+== services.<name>.image.command
+
+
+
+[discrete]
+=== details
+
+Type:: list of strings
+Default::
+
+----
+[]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.image.contents
+
+Top level paths in the container.
+
+
+[discrete]
+=== details
+
+Type:: list of packages
+Default::
+
+----
+[]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.image.name
+
+A human readable name for the docker image.
+
+Shows up in the <code>docker ps</code> output in the
+<code>IMAGE</code> column, among other places.
+
+
+[discrete]
+=== details
+
+Type:: string
+Default::
+
+----
+{"_type":"literalExample","text":"config.service.name"}
+----
+
+
+No Example:: {blank}
+
+== services.<name>.image.nixBuild
+
+Whether to build this image with Nixpkgs'
+<code>dockerTools.buildLayeredImage</code>
+and then load it with <code>docker load</code>.
+
+By default, an image will be built with Nix unless <option>service.image</option>
+is set. See also <option>image.name</option>, which defaults to
+the service name.
+
+
+[discrete]
+=== details
+
+Type:: boolean
+No Default:: {blank}
+
+No Example:: {blank}
+
+== services.<name>.image.rawConfig
+
+This is a low-level fallback for when a container option has not
+been modeled in the Arion module system.
+
+This attribute set does not have an appropriate merge function.
+Please use the specific <code>image</code> options instead.
+
+Run-time configuration of the container. A full list of the
+options are available at in the <link xlink:href="https://github.com/moby/moby/blob/master/image/spec/v1.2.md#image-json-field-descriptions">Docker Image Specification
+v1.2.0</link>.
+
+
+[discrete]
+=== details
+
+Type:: attribute set of unspecifieds
+Default::
+
+----
+{}
+----
+
+
+No Example:: {blank}
+
+== services.<name>.nixos.build
+
+NixOS build products from <code>config.system.build</code>, such as <code>toplevel</code> and <code>etc</code>.
+
+This option is unused by default, because not all images use NixOS.
+
+One way to use this is to enable <code>nixos.useSystemd</code>, but the
+NixOS configuration can be used in other ways.
+
+
+[discrete]
+=== details
+
+Type:: attribute set
+No Default:: {blank}
+Read Only:: {blank}
+No Example:: {blank}
+
+== services.<name>.nixos.configuration
+
+Modules to add to the NixOS configuration.
+
+This option is unused by default, because not all images use NixOS.
+
+One way to use this is to enable <code>nixos.useSystemd</code>, but the
+NixOS configuration can be used in other ways.
+
+
+[discrete]
+=== details
+
+Type:: list of unspecifieds or unspecified convertible to it
+Default::
+
+----
+{}
+----
+
+
+No Example:: {blank}
+
+== services.<name>.nixos.evaluatedConfig
+
+Evaluated NixOS configuration, to be read by service-level modules.
+
+This option is unused by default, because not all images use NixOS.
+
+One way to use this is to enable <code>nixos.useSystemd</code>, but the
+NixOS configuration can be used in other ways.
+
+
+[discrete]
+=== details
+
+Type:: attribute set
+No Default:: {blank}
+Read Only:: {blank}
+No Example:: {blank}
+
+== services.<name>.nixos.useSystemd
+
+When enabled, call the NixOS systemd-based init system.
+
+Configure NixOS with <code>nixos.configuration</code>.
+
+
+[discrete]
+=== details
+
+Type:: boolean
+Default::
+
+----
+false
+----
+
+
+No Example:: {blank}
+
+== services.<name>.out.extendedInfo
+
+Information about a service to include in the Docker Compose file,
+but that will not be used by the <code>docker-compose</code> command
+itself.
+
+It will be inserted in <code>x-arion.serviceInfo.&lt;service.name></code>.
+
+
+[discrete]
+=== details
+
+Type:: attribute set of unspecifieds
+Default::
+
+----
+{}
+----
+
+
+No Example:: {blank}
+
+== services.<name>.out.service
+
+Raw input for the service in <code>docker-compose.yaml</code>.
+
+You should not need to use this option. If anything is
+missing, please contribute the missing option.
+
+This option is user accessible because it may serve as an
+escape hatch for some.
+
+
+[discrete]
+=== details
+
+Type:: attribute set of unspecifieds
+No Default:: {blank}
+
+No Example:: {blank}
+
+== services.<name>.service.build.context
+
+Locates a Dockerfile to use for creating an image to use in this service.
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#context">Docker Compose#context</link>
+
+
+[discrete]
+=== details
+
+Type:: null or string
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.capabilities
+
+Enable/disable linux capabilities, or pick Docker's default.
+
+Setting a capability to <code>true</code> means that it will be
+"added". Setting it to <code>false</code> means that it will be "dropped".
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#cap_add-cap_drop">Docker Compose#cap_add-cap_drop</link>
+
+Omitted and <code>null</code> capabilities will therefore be set
+according to Docker's <link xlink:href="https://docs.docker.com/engine/reference/run/#runtime-privilege-and-linux-capabilities">default list of capabilities.</link>
+
+
+[discrete]
+=== details
+
+Type:: attribute set of null or booleans
+Default::
+
+----
+{}
+----
+
+
+Example::
+
+----
+{"ALL":true,"NET_ADMIN":false,"SYS_ADMIN":false}
+----
+
+
+== services.<name>.service.command
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#command">Docker Compose#command</link>
+
+[discrete]
+=== details
+
+Type:: null or unspecified
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.container_name
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#container_name">Docker Compose#container_name</link>
+
+[discrete]
+=== details
+
+Type:: null or string
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.defaultExec
+
+Container program and arguments to invoke when calling
+<code>arion exec &lt;service.name></code> without further arguments.
+
+
+[discrete]
+=== details
+
+Type:: list of strings
+Default::
+
+----
+["/bin/sh"]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.depends_on
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#depends_on">Docker Compose#depends_on</link>
+
+[discrete]
+=== details
+
+Type:: list of strings
+Default::
+
+----
+[]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.devices
+
+See <link xlink:href="https://docs.docker.com/engine/reference/run/#runtime-privilege-and-linux-capabilities"><code>docker run --device</code> documentation</link>
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#devices">Docker Compose#devices</link>
+
+
+[discrete]
+=== details
+
+Type:: list of strings
+Default::
+
+----
+[]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.entrypoint
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#entrypoint">Docker Compose#entrypoint</link>
+
+[discrete]
+=== details
+
+Type:: null or string
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.env_file
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#env_file">Docker Compose#env_file</link>
+
+[discrete]
+=== details
+
+Type:: list of strings
+Default::
+
+----
+[]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.environment
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#environment">Docker Compose#environment</link>
+
+[discrete]
+=== details
+
+Type:: attribute set of string or signed integers
+Default::
+
+----
+{}
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.expose
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#expose">Docker Compose#expose</link>
+
+[discrete]
+=== details
+
+Type:: list of strings
+Default::
+
+----
+[]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.external_links
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#external_links">Docker Compose#external_links</link>
+
+[discrete]
+=== details
+
+Type:: list of strings
+Default::
+
+----
+[]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.extra_hosts
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#extra_hosts">Docker Compose#extra_hosts</link>
+
+[discrete]
+=== details
+
+Type:: list of strings
+Default::
+
+----
+[]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.hostStoreAsReadOnly
+
+Adds a ':ro' (read-only) access mode to the host nix store bind mount.
+
+[discrete]
+=== details
+
+Type:: boolean
+Default::
+
+----
+true
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.hostname
+
+Analogous to the <code>docker run</code> counterpart.
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#domainname-hostname-ipc-mac_address-privileged-read_only-shm_size-stdin_open-tty-user-working_dir">Docker Compose#domainname-hostname-ipc-mac_address-privileged-read_only-shm_size-stdin_open-tty-user-working_dir</link>
+
+
+[discrete]
+=== details
+
+Type:: null or string
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.image
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#image">Docker Compose#image</link>
+
+[discrete]
+=== details
+
+Type:: string
+No Default:: {blank}
+
+No Example:: {blank}
+
+== services.<name>.service.links
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#links">Docker Compose#links</link>
+
+[discrete]
+=== details
+
+Type:: list of strings
+Default::
+
+----
+[]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.name
+
+The name of the service - <code>&lt;name></code> in the composition-level <code>services.&lt;name></code>
+
+
+[discrete]
+=== details
+
+Type:: string
+No Default:: {blank}
+Read Only:: {blank}
+No Example:: {blank}
+
+== services.<name>.service.network_mode
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#network_mode">Docker Compose#network_mode</link>
+
+[discrete]
+=== details
+
+Type:: null or string
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.networks
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#networks">Docker Compose#networks</link>
+
+[discrete]
+=== details
+
+Type:: null or list of strings
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.ports
+
+Expose ports on host. "host:container" or structured.
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#ports">Docker Compose#ports</link>
+
+
+[discrete]
+=== details
+
+Type:: list of unspecifieds
+Default::
+
+----
+[]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.privileged
+
+Analogous to the <code>docker run</code> counterpart.
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#domainname-hostname-ipc-mac_address-privileged-read_only-shm_size-stdin_open-tty-user-working_dir">Docker Compose#domainname-hostname-ipc-mac_address-privileged-read_only-shm_size-stdin_open-tty-user-working_dir</link>
+
+
+[discrete]
+=== details
+
+Type:: null or boolean
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.restart
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#restart">Docker Compose#restart</link>
+
+[discrete]
+=== details
+
+Type:: null or string
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.stop_signal
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#stop_signal">Docker Compose#stop_signal</link>
+
+[discrete]
+=== details
+
+Type:: null or string
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.sysctls
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#sysctls">Docker Compose#sysctls</link>
+
+[discrete]
+=== details
+
+Type:: attribute set of string or signed integers
+Default::
+
+----
+{}
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.tmpfs
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#tmpfs">Docker Compose#tmpfs</link>
+
+[discrete]
+=== details
+
+Type:: list of strings
+Default::
+
+----
+[]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.tty
+
+Analogous to the <code>docker run</code> counterpart.
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#domainname-hostname-ipc-mac_address-privileged-read_only-shm_size-stdin_open-tty-user-working_dir">Docker Compose#domainname-hostname-ipc-mac_address-privileged-read_only-shm_size-stdin_open-tty-user-working_dir</link>
+
+
+[discrete]
+=== details
+
+Type:: null or boolean
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.useHostNixDaemon
+
+Make the host Nix daemon available.
+
+[discrete]
+=== details
+
+Type:: boolean
+Default::
+
+----
+false
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.useHostStore
+
+Bind mounts the host store if enabled, avoiding copying.
+
+[discrete]
+=== details
+
+Type:: boolean
+Default::
+
+----
+false
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.user
+
+Analogous to the <code>docker run</code> counterpart.
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#domainname-hostname-ipc-mac_address-privileged-read_only-shm_size-stdin_open-tty-user-working_dir">Docker Compose#domainname-hostname-ipc-mac_address-privileged-read_only-shm_size-stdin_open-tty-user-working_dir</link>
+
+
+[discrete]
+=== details
+
+Type:: null or string
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.volumes
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#volumes">Docker Compose#volumes</link>
+
+[discrete]
+=== details
+
+Type:: list of unspecifieds
+Default::
+
+----
+[]
+----
+
+
+No Example:: {blank}
+
+== services.<name>.service.working_dir
+
+Analogous to the <code>docker run</code> counterpart.
+
+See <link xlink:href="https://docs.docker.com/compose/compose-file/#domainname-hostname-ipc-mac_address-privileged-read_only-shm_size-stdin_open-tty-user-working_dir">Docker Compose#domainname-hostname-ipc-mac_address-privileged-read_only-shm_size-stdin_open-tty-user-working_dir</link>
+
+
+[discrete]
+=== details
+
+Type:: null or string
+Default::
+
+----
+null
+----
+
+
+No Example:: {blank}
+
--- a/docs/options.nix
+++ b/docs/options.nix
@ -8,12 +8,10 @@ let
    options = eval.options;
  };

-in (pkgs.runCommand "agent-options.adoc" { } ''
-  cat >$out <<EOF
+in (pkgs.writeText "agent-options" ''
  = Arion options

-  EOF
-  cat ${options.optionsAsciiDoc} >>$out
+  ${options.optionsAsciiDoc}
 '').overrideAttrs (o: {
  # Work around https://github.com/hercules-ci/hercules-ci-agent/issues/168
  allowSubstitutes = true;
--- a/examples/flake/arion-compose.nix
+++ b/examples/flake/arion-compose.nix
@ -1,30 +0,0 @@
-{ pkgs, ... }:
-let 
-    sh = pkgs.stdenv.mkDerivation {
-        name = "sh";
-        phases = [ "installPhase" ];
-
-        installPhase = ''
-            mkdir -p "$out"/bin
-            ln -s ${pkgs.bash}/bin/sh "$out"/bin/sh
-        '';
-    };
-in{
-  config.project.name = "webapp";
-  config.services = {
-
-    webserver = {
-      image.contents = [ sh ];
-      service.useHostStore = true;
-      service.command = [ "sh" "-c" ''
-                  cd "$$WEB_ROOT"
-                  ${pkgs.python3}/bin/python -m http.server
-                '' ];
-      service.ports = [
-        "8000:8000" # host:container
-      ];
-      service.environment.WEB_ROOT = "${pkgs.nix.doc}/share/doc/nix/manual";
-      service.stop_signal = "SIGINT";
-    };
-  };
-}
--- a/examples/flake/arion-pkgs.nix
+++ b/examples/flake/arion-pkgs.nix
@ -1,13 +0,0 @@
-let
-  flake = if builtins ? getFlake
-    then (builtins.getFlake (toString ./.)).pkgs
-    else (import flake-compat { src = ./.; }).defaultNix;
-  # NB: this is lazy
-  lock = builtins.fromJSON (builtins.readFile ./flake.lock);
-  inherit (lock.nodes.flake-compat.locked) owner repo rev narHash;
-  flake-compat = builtins.fetchTarball {
-    url = "https://github.com/${owner}/${repo}/archive/${rev}.tar.gz";
-    sha256 = narHash;
-  };
-in
-  flake.pkgs
--- a/examples/flake/flake.lock
+++ b/examples/flake/flake.lock
@ -1,44 +0,0 @@
-{
-  "nodes": {
-    "flake-compat": {
-      "flake": false,
-      "locked": {
-        "lastModified": 1606424373,
-        "narHash": "sha256-oq8d4//CJOrVj+EcOaSXvMebvuTkmBJuT5tzlfewUnQ=",
-        "owner": "edolstra",
-        "repo": "flake-compat",
-        "rev": "99f1c2157fba4bfe6211a321fd0ee43199025dbf",
-        "type": "github"
-      },
-      "original": {
-        "owner": "edolstra",
-        "repo": "flake-compat",
-        "type": "github"
-      }
-    },
-    "nixpkgs": {
-      "locked": {
-        "lastModified": 1618853290,
-        "narHash": "sha256-K4fddnrGOcKL+6CEchRrVmepiwvwvHxB87goqBTI5Bs=",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "9a1672105db0eebe8ef59f310397435f2d0298d0",
-        "type": "github"
-      },
-      "original": {
-        "owner": "NixOS",
-        "ref": "nixos-20.09",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
-    "root": {
-      "inputs": {
-        "flake-compat": "flake-compat",
-        "nixpkgs": "nixpkgs"
-      }
-    }
-  },
-  "root": "root",
-  "version": 7
-}
--- a/examples/flake/flake.nix
+++ b/examples/flake/flake.nix
@ -1,19 +0,0 @@
-{
-  description = "A very basic flake";
-
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-20.09";
-  inputs.flake-compat.url = "github:edolstra/flake-compat";
-  inputs.flake-compat.flake = false;
-
-  outputs = { self, nixpkgs, ... }: {
-
-    pkgs = nixpkgs.legacyPackages.x86_64-linux;
-    # # alternative:
-    # pkgs = import nixpkgs { config = { }; overlays = [ ]; system = "x86_64-linux"; };
-
-    packages.x86_64-linux.hello = nixpkgs.legacyPackages.x86_64-linux.hello;
-
-    defaultPackage.x86_64-linux = self.packages.x86_64-linux.hello;
-
-  };
-}
--- a/examples/full-nixos/arion-compose.nix
+++ b/examples/full-nixos/arion-compose.nix
@ -1,15 +1,9 @@
 {
-  project.name = "full-nixos";
-  services.webserver = { pkgs, lib, ... }: {
+  services.webserver = { pkgs, ... }: {
    nixos.useSystemd = true;
-    nixos.configuration.boot.tmp.useTmpfs = true;
-    nixos.configuration.networking.useDHCP = false;
+    nixos.configuration.boot.tmpOnTmpfs = true;
    nixos.configuration.services.nginx.enable = true;
    nixos.configuration.services.nginx.virtualHosts.localhost.root = "${pkgs.nix.doc}/share/doc/nix/manual";
-    nixos.configuration.services.nscd.enable = false;
-    nixos.configuration.system.nssModules = lib.mkForce [];
-    nixos.configuration.systemd.services.nginx.serviceConfig.AmbientCapabilities = 
-      lib.mkForce [ "CAP_NET_BIND_SERVICE" ];
    service.useHostStore = true;
    service.ports = [
      "8000:80" # host:container
--- a/examples/minimal/arion-compose.nix
+++ b/examples/minimal/arion-compose.nix
@ -1,10 +1,8 @@
 { pkgs, ... }:
 {
-  project.name = "webapp";
-  services = {
+  config.services = {

    webserver = {
-      image.enableRecommendedContents = true;
      service.useHostStore = true;
      service.command = [ "sh" "-c" ''
                  cd "$$WEB_ROOT"
@ -14,7 +12,6 @@
        "8000:8000" # host:container
      ];
      service.environment.WEB_ROOT = "${pkgs.nix.doc}/share/doc/nix/manual";
-      service.stop_signal = "SIGINT";
    };
  };
 }
--- a/examples/nixos-unit/arion-compose.nix
+++ b/examples/nixos-unit/arion-compose.nix
@ -17,27 +17,17 @@
 */

 {
-  project.name = "nixos-unit";
  services.webserver = { config, pkgs, ... }: {

-    nixos.configuration = {config, lib, options, pkgs, ...}: {
+    nixos.configuration = {config, pkgs, ...}: {
      boot.isContainer = true;
-      services.nginx = {
-        enable = true;
-        virtualHosts.localhost.root = "${pkgs.nix.doc}/share/doc/nix/manual";
-      } // lib.optionalAttrs (options?services.nginx.stateDir) {
-        # Work around a problem in NixOS 20.03
-        stateDir = "/var/lib/nginx";
-      };
+      services.nginx.enable = true;
+      services.nginx.virtualHosts.localhost.root = "${pkgs.nix.doc}/share/doc/nix/manual";
      system.build.run-nginx = pkgs.writeScript "run-nginx" ''
        #!${pkgs.bash}/bin/bash
        PATH='${config.systemd.services.nginx.environment.PATH}'
        echo nginx:x:${toString config.users.users.nginx.uid}:${toString config.users.groups.nginx.gid}:nginx web server user:/var/empty:/bin/sh >>/etc/passwd
        echo nginx:x:${toString config.users.groups.nginx.gid}:nginx >>/etc/group
-        echo 'nobody:x:65534:65534:Unprivileged account do not use:/var/empty:/run/current-system/sw/bin/nologin' >>/etc/passwd
-        echo 'nogroup:x:65534:' >>/etc/group
-        mkdir -p /var/log/nginx /run/nginx/ /var/cache/nginx /var/lib/nginx/{,logs,proxy_temp,client_body_temp,fastcgi_temp,scgi_temp,uwsgi_temp} /tmp/nginx_client_body
-        chown nginx /var/log/nginx /run/nginx/ /var/cache/nginx /var/lib/nginx/{,logs,proxy_temp,client_body_temp,fastcgi_temp,scgi_temp,uwsgi_temp} /tmp/nginx_client_body
        ${config.systemd.services.nginx.runner}
      '';
    };
--- a/examples/traefik/arion-compose.nix
+++ b/examples/traefik/arion-compose.nix
@ -1,64 +0,0 @@
-/*
- 
-  An example of
-   - traefik HTTP reverse proxy
-   - minimal images
-   - routing via docker labels
-
-  Run `arion up -d` and open http://nix-docs.localhost/
-
- */
-{ lib, pkgs, ... }: {
-  config.project.name = "traefik";
-  config.networks = {
-    traefik-custom = {
-      name = "traefik-custom";
-      ipam = {
-        config = [{
-          subnet = "172.32.0.0/16";
-          gateway = "172.32.0.1";
-        }];
-      };
-    };
-  };
-  config.services = {
-    traefik = {
-      image.command = [
-        "${pkgs.traefik}/bin/traefik"
-        "--api.insecure=true"
-        "--providers.docker=true"
-        "--providers.docker.exposedbydefault=false"
-        "--entrypoints.web.address=:80"
-      ];
-      service = {
-        container_name = "traefik";
-        stop_signal = "SIGINT";
-        ports = [ "80:80" "8080:8080" ];
-        volumes = [ "/var/run/docker.sock:/var/run/docker.sock:ro" ];
-        networks = [ "traefik-custom" ];
-      };
-    };
-
-    nix-docs = {
-      image.command = ["${pkgs.writeScript "entrypoint" ''
-        #!${pkgs.bash}/bin/bash
-        cd ${pkgs.nix.doc}/share/doc/nix/manual
-        ${pkgs.python3}/bin/python -m http.server
-      ''}"];
-      service.container_name = "simple-service";
-      service.stop_signal = "SIGINT";
-      service.labels = {
-        "traefik.enable" = "true";
-        "traefik.http.routers.nix-docs.rule" = "Host(`nix-docs.localhost`)";
-        "traefik.http.routers.nix-docs.entrypoints" = "web";
-        "traefik.http.services.nix-docs.loadBalancer.server.port" = "8000";
-      };
-      service.networks = {
-        traefik-custom = {
-          ipv4_address = "172.32.0.5";
-        };
-      };
-    };
-  };
-}
-
--- a/examples/traefik/arion-pkgs.nix
+++ b/examples/traefik/arion-pkgs.nix
@ -1,6 +0,0 @@
-# Instead of pinning Nixpkgs, we can opt to use the one in NIX_PATH
-import <nixpkgs> {
-  # We specify the architecture explicitly. Use a Linux remote builder when
-  # calling arion from other platforms.
-  system = "x86_64-linux";
-}
--- a/flake.lock
+++ b/flake.lock
@ -1,107 +0,0 @@
-{
-  "nodes": {
-    "flake-parts": {
-      "inputs": {
-        "nixpkgs-lib": [
-          "nixpkgs"
-        ]
-      },
-      "locked": {
-        "lastModified": 1722555600,
-        "narHash": "sha256-XOQkdLafnb/p9ij77byFQjDf5m5QYl9b2REiVClC+x4=",
-        "owner": "hercules-ci",
-        "repo": "flake-parts",
-        "rev": "8471fe90ad337a8074e957b69ca4d0089218391d",
-        "type": "github"
-      },
-      "original": {
-        "owner": "hercules-ci",
-        "repo": "flake-parts",
-        "type": "github"
-      }
-    },
-    "flake-parts_2": {
-      "inputs": {
-        "nixpkgs-lib": [
-          "hercules-ci-effects",
-          "nixpkgs"
-        ]
-      },
-      "locked": {
-        "lastModified": 1712014858,
-        "narHash": "sha256-sB4SWl2lX95bExY2gMFG5HIzvva5AVMJd4Igm+GpZNw=",
-        "owner": "hercules-ci",
-        "repo": "flake-parts",
-        "rev": "9126214d0a59633752a136528f5f3b9aa8565b7d",
-        "type": "github"
-      },
-      "original": {
-        "id": "flake-parts",
-        "type": "indirect"
-      }
-    },
-    "haskell-flake": {
-      "locked": {
-        "lastModified": 1675296942,
-        "narHash": "sha256-u1X1sblozi5qYEcLp1hxcyo8FfDHnRUVX3dJ/tW19jY=",
-        "owner": "srid",
-        "repo": "haskell-flake",
-        "rev": "c2cafce9d57bfca41794dc3b99c593155006c71e",
-        "type": "github"
-      },
-      "original": {
-        "owner": "srid",
-        "ref": "0.1.0",
-        "repo": "haskell-flake",
-        "type": "github"
-      }
-    },
-    "hercules-ci-effects": {
-      "inputs": {
-        "flake-parts": "flake-parts_2",
-        "nixpkgs": [
-          "nixpkgs"
-        ]
-      },
-      "locked": {
-        "lastModified": 1719226092,
-        "narHash": "sha256-YNkUMcCUCpnULp40g+svYsaH1RbSEj6s4WdZY/SHe38=",
-        "owner": "hercules-ci",
-        "repo": "hercules-ci-effects",
-        "rev": "11e4b8dc112e2f485d7c97e1cee77f9958f498f5",
-        "type": "github"
-      },
-      "original": {
-        "owner": "hercules-ci",
-        "repo": "hercules-ci-effects",
-        "type": "github"
-      }
-    },
-    "nixpkgs": {
-      "locked": {
-        "lastModified": 1722630782,
-        "narHash": "sha256-hMyG9/WlUi0Ho9VkRrrez7SeNlDzLxalm9FwY7n/Noo=",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "d04953086551086b44b6f3c6b7eeb26294f207da",
-        "type": "github"
-      },
-      "original": {
-        "owner": "NixOS",
-        "ref": "nixos-unstable",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
-    "root": {
-      "inputs": {
-        "flake-parts": "flake-parts",
-        "haskell-flake": "haskell-flake",
-        "hercules-ci-effects": "hercules-ci-effects",
-        "nixpkgs": "nixpkgs"
-      }
-    }
-  },
-  "root": "root",
-  "version": 7
-}
--- a/flake.nix
+++ b/flake.nix
@ -1,98 +0,0 @@
-{
-  description = "Arion - use Docker Compose via Nix";
-
-  inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
-    haskell-flake.url = "github:srid/haskell-flake/0.1.0";
-    flake-parts.url = "github:hercules-ci/flake-parts";
-    flake-parts.inputs.nixpkgs-lib.follows = "nixpkgs";
-    hercules-ci-effects.url = "github:hercules-ci/hercules-ci-effects";
-    hercules-ci-effects.inputs.nixpkgs.follows = "nixpkgs";
-  };
-
-  outputs = inputs@{ self, flake-parts, ... }:
-    flake-parts.lib.mkFlake { inherit inputs; } ({ config, lib, extendModules, ... }: {
-      imports = [
-        inputs.haskell-flake.flakeModule
-        inputs.hercules-ci-effects.flakeModule
-        inputs.flake-parts.flakeModules.easyOverlay
-        ./docs/flake-module.nix
-        ./tests/flake-module.nix
-      ];
-      systems = inputs.nixpkgs.lib.systems.flakeExposed;
-      perSystem = { config, self', inputs', pkgs, system, final, ... }:
-        let h = pkgs.haskell.lib.compose; in
-        {
-          overlayAttrs = {
-            inherit (config.packages) arion;
-            arionTestingFlags = {
-              dockerSupportsSystemd = false;
-            };
-          };
-          packages.default = config.packages.arion;
-          packages.overlay-test = final.arion;
-          packages.arion = import ./nix/arion.nix { inherit pkgs; };
-          haskellProjects.haskell-package = {
-            # not autodetected: https://github.com/srid/haskell-flake/issues/49
-            packages.arion-compose.root = ./.;
-
-            overrides =
-              self: super: {
-                arion-compose =
-                  lib.pipe super.arion-compose [
-                    (h.addBuildTools [ pkgs.nix ])
-                    (h.overrideCabal (o: {
-                      src = pkgs.lib.sourceByRegex ./. [
-                        ".*[.]cabal"
-                        "LICENSE"
-                        "src/?.*"
-                        "README.asciidoc"
-                        "CHANGELOG.md"
-                      ];
-                      preCheck = ''
-                        export NIX_LOG_DIR=$TMPDIR
-                        export NIX_STATE_DIR=$TMPDIR
-                        export NIX_PATH=nixpkgs=${pkgs.path}
-                      '';
-                    }))
-                  ];
-              };
-          };
-          devShells.default = config.devShells.haskell-package.overrideAttrs (o: {
-            nativeBuildInputs = o.nativeBuildInputs or [ ] ++ [
-              pkgs.docker-compose
-              pkgs.nixpkgs-fmt
-              config.haskellProjects.haskell-package.haskellPackages.releaser
-            ];
-          });
-        };
-
-      hercules-ci.flake-update = {
-        enable = true;
-        autoMergeMethod = "merge";
-        when = {
-          hour = [ 2 ];
-          dayOfMonth = [ 5 ];
-        };
-      };
-
-      herculesCI.ciSystems = [
-        # "aarch64-darwin"
-        # "aarch64-linux"
-        "x86_64-darwin"
-        "x86_64-linux"
-      ];
-
-      flake = {
-        debug = { inherit inputs config lib; };
-
-        lib = {
-          eval = import ./src/nix/eval-composition.nix;
-          build = args@{ ... }:
-            let composition = self.lib.eval args;
-            in composition.config.out.dockerComposeYaml;
-        };
-        nixosModules.arion = ./nixos-module.nix;
-      };
-    });
-}
--- a/12
+++ b/12
@ -0,0 +1,12 @@
+#!/usr/bin/env nix-shell
+#!nix-shell ./shell.nix
+#!nix-shell -i bash
+set -eux -o pipefail
+
+cd "$(dirname "${BASH_SOURCE[0]}")"
+
+ghcid \
+  --command 'ghci -isrc/haskell/exe src/haskell/exe/Main.hs' \
+  --reload=src/haskell \
+  --restart=arion-compose.cabal \
+  ;
--- a/nix/arion.nix
+++ b/nix/arion.nix
@ -1,13 +1,42 @@
-# Like the upstreamable expression but wired up for the local arion.
 { pkgs ? import ./. {}
 , lib ? pkgs.lib
-, haskell ? pkgs.haskell
 , haskellPackages ? pkgs.haskellPackages
 , arion-compose ? import ./haskell-arion-compose.nix { inherit pkgs haskellPackages; }
-, runCommand ? pkgs.runCommand
 }:
-import ./upstreamable/default.nix {
-  inherit pkgs lib haskell runCommand;
-  haskellPackages = haskellPackages // { inherit arion-compose; };
-  evalSrc = ./..;
-}
+
+let
+  inherit (pkgs.haskell.lib) justStaticExecutables overrideCabal;
+
+  srcDir = ../src;
+  eval = import (srcDir + "/nix/eval-composition.nix");
+  build = args@{...}:
+    let composition = eval args;
+    in composition.config.out.dockerComposeYaml;
+
+in
+  justStaticExecutables (overrideCabal arion-compose (o: {
+    buildTools = o.buildTools ++ [pkgs.makeWrapper];
+    passthru = o.passthru // {
+      inherit eval build;
+    };
+    pname = "arion"; # Cover up the needlessly long Haskell package name
+
+    # PYTHONPATH
+    #
+    # We close off the python module search path!
+    #
+    # Accepting directories from the environment into the search path
+    # tends to break things. Docker Compose does not have a plugin
+    # system as far as I can tell, so I don't expect this to break a
+    # feature, but rather to make the program more robustly self-
+    # contained.
+
+    postInstall = ''${o.postInstall or ""}
+      mkdir -p $out/libexec
+      mv $out/bin/arion $out/libexec
+      makeWrapper $out/libexec/arion $out/bin/arion \
+        --unset PYTHONPATH \
+        --prefix PATH : ${lib.makeBinPath [ pkgs.docker-compose ]} \
+        ;
+    '';
+  }))
--- a/nix/ci.nix
+++ b/nix/ci.nix
@ -0,0 +1,43 @@
+let
+  sources = import ./sources.nix;
+  lib = import (sources."nixpkgs" + "/lib");
+  inherit (import sources."project.nix" { inherit lib; }) dimension;
+in
+
+dimension "Nixpkgs version" {
+    "nixos-19_03" = {
+      nixpkgsSource = "nixpkgs";
+      isReferenceNixpkgs = true;
+      enableDoc = false;
+    };
+    "nixos-19_09" = {
+      nixpkgsSource = "nixos-19.09";
+      enableDoc = true;
+    };
+    "nixos-unstable" = {
+      nixpkgsSource = "nixos-unstable";
+      enableDoc = true;
+    };
+  } (
+    _name: { nixpkgsSource, isReferenceNixpkgs ? false, enableDoc ? true }:
+
+
+      dimension "System" {
+        "x86_64-linux" = { isReferenceTarget = isReferenceNixpkgs; };
+        "x86_64-darwin" = { enableNixOSTests = false; };
+      } (
+        system: { isReferenceTarget ? false, enableNixOSTests ? true }:
+          let
+            pkgs = import ./. { inherit system; nixpkgsSrc = sources.${nixpkgsSource}; };
+          in
+          {
+            inherit (pkgs) arion;
+          } // lib.optionalAttrs enableNixOSTests {
+            inherit (pkgs) tests;
+          } // lib.optionalAttrs enableDoc {
+            inherit (pkgs) doc doc-options doc-options-check;
+          } // lib.optionalAttrs isReferenceTarget {
+            inherit (pkgs.arion-project.haskellPkgs) arion-compose-checked;
+          }
+      )
+  )
--- a/nix/compat.nix
+++ b/nix/compat.nix
@ -1,10 +0,0 @@
-(import
-  (
-    let lock = builtins.fromJSON (builtins.readFile ./flake.lock); in
-    fetchTarball {
-      url = "https://github.com/edolstra/flake-compat/archive/009399224d5e398d03b22badca40a37ac85412a1.tar.gz";
-      sha256 = "sha256:0xcr9fibnapa12ywzcnlf54wrmbqqb96fmmv8043zhsycws7bpqy";
-    }
-  )
-  { src = ../.; }
-).defaultNix
--- a/nix/default.nix
+++ b/nix/default.nix
@ -0,0 +1,17 @@
+{ sources ? import ./sources.nix
+, nixpkgsName ? "nixos-19.09"
+, nixpkgsSrc ? sources.${nixpkgsName}
+, system ? builtins.currentSystem
+, ...
+}:
+
+import nixpkgsSrc ({
+  # Makes the config pure as well. See <nixpkgs>/top-level/impure.nix:
+  config = {
+  };
+  overlays = [
+    # all the packages are defined there:
+    (import ./overlay.nix)
+  ];
+  inherit system;
+})
--- a/nix/haskell-arion-compose.nix
+++ b/nix/haskell-arion-compose.nix
@ -6,12 +6,6 @@ let
  inherit (pkgs.haskell.lib) overrideCabal addBuildTools;
 in
  overrideCabal (addBuildTools (haskellPackages.callCabal2nix "arion-compose" ./.. {}) [pkgs.nix]) (o: o // {
-    src = pkgs.lib.sourceByRegex ../. [
-      ".*[.]cabal"
-      "LICENSE"
-      "src/?.*"
-      "README.asciidoc"
-    ];
    preCheck = ''
      export NIX_LOG_DIR=$TMPDIR
      export NIX_STATE_DIR=$TMPDIR
--- a/nix/haskell-overlay.nix
+++ b/nix/haskell-overlay.nix
@ -0,0 +1,16 @@
+self: super: hself: hsuper:
+{
+  arion-compose = import ./haskell-arion-compose.nix { pkgs = self; haskellPackages = hself; };
+  arion-compose-checked =
+              let pkg = super.haskell.lib.buildStrictly hself.arion-compose;
+                  checked = super.haskell.lib.overrideCabal pkg (o: {
+                    postConfigure = ''${o.postConfigure or ""}
+                      if ! ${hsuper.cabal-install}/bin/cabal check;
+                      then
+                        echo 1>&2 ERROR: cabal file is invalid. Above warnings were errors.
+                        exit 1
+                      fi
+                    '';
+                  });
+              in checked;
+}
--- a/nix/overlay.nix
+++ b/nix/overlay.nix
@ -0,0 +1,53 @@
+self: super:
+let
+  inherit (self.arion-project) haskellPkgs;
+  inherit (super) lib;
+
+  sources = import ./sources.nix;
+
+  fakeRepo = src: super.runCommand "source" { inherit src; buildInputs = [super.git]; } ''
+    cp -r --no-preserve=mode $src $out
+    git init
+    cp -r .git $out
+  '';
+
+in
+{
+
+  inherit (import ./.. { pkgs = self; }) arion;
+  tests = super.callPackage ../tests {};
+
+  doc-options = import ../docs/options.nix {};
+  doc-options-check = self.runCommand "doc-options-check" {} ''
+    diff --color -u ${../docs/modules/ROOT/partials/NixOSOptions.adoc} ${self.doc-options}
+    touch $out
+  '';
+  doc = self.stdenv.mkDerivation { 
+    name = "arion-documentation"; 
+    buildInputs = [super.antora]; 
+    src = fakeRepo ../.;
+    HOME = ".";
+    buildPhase = "antora antora-playbook";
+    installPhase = ''
+      mkdir $out
+      mv public/* $out/
+    '';
+  };
+
+  arion-project = super.recurseIntoAttrs {
+    haskellPkgs = super.haskellPackages.extend (import ./haskell-overlay.nix self super);
+    shell = haskellPkgs.shellFor {
+      packages = p: [p.arion-compose];
+      buildInputs = [
+        haskellPkgs.cabal-install
+        haskellPkgs.ghcid
+        super.docker-compose
+        self.niv
+        self.releaser
+      ];
+    };
+  };
+
+  inherit (import (sources.niv) {}) niv;
+  releaser = self.haskellPackages.callCabal2nix "releaser" sources.releaser {};
+}
--- a/nix/sources.json
+++ b/nix/sources.json
@ -0,0 +1,75 @@
+{
+    "niv": {
+        "branch": "master",
+        "description": "Easy dependency management for Nix projects",
+        "homepage": "https://github.com/nmattia/niv",
+        "owner": "nmattia",
+        "repo": "niv",
+        "rev": "1dd094156b249586b66c16200ecfd365c7428dc0",
+        "sha256": "1b2vjnn8iac5iiqszjc2v1s1ygh0yri998c0k3s4x4kn0dsqik21",
+        "type": "tarball",
+        "url": "https://github.com/nmattia/niv/archive/1dd094156b249586b66c16200ecfd365c7428dc0.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixos-19.09": {
+        "branch": "nixos-19.09",
+        "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
+        "homepage": "https://github.com/NixOS/nixpkgs",
+        "owner": "NixOS",
+        "repo": "nixpkgs-channels",
+        "rev": "3ba0d9f75ccffd41e32cfea4046805f8bbab12f5",
+        "sha256": "0w20drs4mwlq12k1sss1x8adyf5ph5jd52n8wdcgmn4sm60qjmki",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs-channels/archive/3ba0d9f75ccffd41e32cfea4046805f8bbab12f5.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixos-unstable": {
+        "branch": "nixos-unstable",
+        "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
+        "homepage": "https://github.com/NixOS/nixpkgs",
+        "owner": "NixOS",
+        "repo": "nixpkgs-channels",
+        "rev": "cb4332e3eb6dfdb653f1fc7397a0292df228a533",
+        "sha256": "1722wphznqhpfny08rcy19l85r2l893ckjc3h1vfivj6aj64fwjr",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs-channels/archive/cb4332e3eb6dfdb653f1fc7397a0292df228a533.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz",
+        "version": ""
+    },
+    "nixpkgs": {
+        "branch": "nixos-19.03",
+        "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
+        "homepage": "https://github.com/NixOS/nixpkgs",
+        "owner": "NixOS",
+        "repo": "nixpkgs-channels",
+        "rev": "d15a31f88a261281cd7c79038ae860c5ed95507d",
+        "sha256": "038iqfwmppnxq6aa89qm6k98lhwg686bmc9qjifibddm8pcp2wd0",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs-channels/archive/d15a31f88a261281cd7c79038ae860c5ed95507d.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "project.nix": {
+        "branch": "master",
+        "description": "A configuration manager for your projects",
+        "homepage": null,
+        "owner": "hercules-ci",
+        "repo": "project.nix",
+        "rev": "33e5f3cb25feff4ccd00f8c60a05976e2ee01802",
+        "sha256": "0c3q3il5h6q3ms8m6da51knvjsfvpz12sh3a3av4d2a5ikm5ncl1",
+        "type": "tarball",
+        "url": "https://github.com/hercules-ci/project.nix/archive/33e5f3cb25feff4ccd00f8c60a05976e2ee01802.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "releaser": {
+        "branch": "master",
+        "description": "Automation of Haskell package release process.",
+        "homepage": null,
+        "owner": "domenkozar",
+        "repo": "releaser",
+        "rev": "43a4e27654f388e8eacab631e24e26792ff88fe2",
+        "sha256": "072jlbw0hdc4nvs9frd7wdyzdv4mz2dc5ib35iaqi9rzdafq6822",
+        "type": "tarball",
+        "url": "https://github.com/domenkozar/releaser/archive/43a4e27654f388e8eacab631e24e26792ff88fe2.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    }
+}
--- a/nix/sources.nix
+++ b/nix/sources.nix
@ -0,0 +1,93 @@
+# This file has been generated by Niv.
+
+# A record, from name to path, of the third-party packages
+with rec
+{
+  pkgs =
+    if hasNixpkgsPath
+    then
+        if hasThisAsNixpkgsPath
+        then import (builtins_fetchTarball { inherit (sources_nixpkgs) url sha256; }) {}
+        else import <nixpkgs> {}
+    else
+        import (builtins_fetchTarball { inherit (sources_nixpkgs) url sha256; }) {};
+
+  sources_nixpkgs =
+    if builtins.hasAttr "nixpkgs" sources
+    then sources.nixpkgs
+    else abort
+    ''
+        Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
+        add a package called "nixpkgs" to your sources.json.
+    '';
+
+  # fetchTarball version that is compatible between all the versions of Nix
+  builtins_fetchTarball =
+      { url, sha256 }@attrs:
+      let
+        inherit (builtins) lessThan nixVersion fetchTarball;
+      in
+        if lessThan nixVersion "1.12" then
+          fetchTarball { inherit url; }
+        else
+          fetchTarball attrs;
+
+  # fetchurl version that is compatible between all the versions of Nix
+  builtins_fetchurl =
+      { url, sha256 }@attrs:
+      let
+        inherit (builtins) lessThan nixVersion fetchurl;
+      in
+        if lessThan nixVersion "1.12" then
+          fetchurl { inherit url; }
+        else
+          fetchurl attrs;
+
+  # A wrapper around pkgs.fetchzip that has inspectable arguments,
+  # annoyingly this means we have to specify them
+  fetchzip = { url, sha256 }@attrs: pkgs.fetchzip attrs;
+
+  # A wrapper around pkgs.fetchurl that has inspectable arguments,
+  # annoyingly this means we have to specify them
+  fetchurl = { url, sha256 }@attrs: pkgs.fetchurl attrs;
+
+  hasNixpkgsPath = (builtins.tryEval <nixpkgs>).success;
+  hasThisAsNixpkgsPath =
+    (builtins.tryEval <nixpkgs>).success && <nixpkgs> == ./.;
+
+  sources = builtins.fromJSON (builtins.readFile ./sources.json);
+
+  mapAttrs = builtins.mapAttrs or
+    (f: set: with builtins;
+      listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set)));
+
+  # borrowed from nixpkgs
+  functionArgs = f: f.__functionArgs or (builtins.functionArgs f);
+  callFunctionWith = autoArgs: f: args:
+    let auto = builtins.intersectAttrs (functionArgs f) autoArgs;
+    in f (auto // args);
+
+  getFetcher = spec:
+    let fetcherName =
+      if builtins.hasAttr "type" spec
+      then builtins.getAttr "type" spec
+      else "builtin-tarball";
+    in builtins.getAttr fetcherName {
+      "tarball" = fetchzip;
+      "builtin-tarball" = builtins_fetchTarball;
+      "file" = fetchurl;
+      "builtin-url" = builtins_fetchurl;
+    };
+};
+# NOTE: spec must _not_ have an "outPath" attribute
+mapAttrs (_: spec:
+  if builtins.hasAttr "outPath" spec
+  then abort
+    "The values in sources.json should not have an 'outPath' attribute"
+  else
+    if builtins.hasAttr "url" spec && builtins.hasAttr "sha256" spec
+    then
+      spec //
+      { outPath = callFunctionWith spec (getFetcher spec) { }; }
+    else spec
+  ) sources
--- a/nix/upstreamable/default.nix
+++ b/nix/upstreamable/default.nix
@ -1,88 +0,0 @@
-args@
-{ pkgs
-, lib
-, haskellPackages
-, haskell
-, runCommand
-
-  # Allow this expression file to be used more efficiently in situations where
-  # the sources are more readily available. Unpacking haskellPackages.arion-compose.src
-  # is not always the best choice for arion.eval.
-, evalSrc ? null
-}:
-
-let
-
-  /* This derivation builds the arion tool.
-
-     It is based on the arion-compose Haskell package, but adapted and extended to
-       - have the correct name
-       - have a smaller closure size
-       - have functions to use Arion from inside Nix: arion.eval and arion.build
-       - make it self-contained by including docker-compose
-   */
-  arion =
-    justStaticExecutables (
-      overrideCabal
-        arion-compose
-        cabalOverrides
-      );
-
-  inherit (haskell.lib) justStaticExecutables overrideCabal;
-
-  inherit (haskellPackages) arion-compose;
-
-  cabalOverrides = o: {
-    buildTools = (o.buildTools or []) ++ [pkgs.makeWrapper];
-    passthru = (o.passthru or {}) // {
-      inherit eval build;
-    };
-    # Patch away the arion-compose name. Unlike the Haskell library, the program
-    # is called arion (arion was already taken on hackage).
-    pname = "arion";
-    src = arion-compose.src;
-
-    # PYTHONPATH
-    #
-    # We close off the python module search path!
-    #
-    # Accepting directories from the environment into the search path
-    # tends to break things. Docker Compose does not have a plugin
-    # system as far as I can tell, so I don't expect this to break a
-    # feature, but rather to make the program more robustly self-
-    # contained.
-
-    postInstall = ''${o.postInstall or ""}
-      mkdir -p $out/libexec
-      mv $out/bin/arion $out/libexec
-      makeWrapper $out/libexec/arion $out/bin/arion \
-        --unset PYTHONPATH \
-        --prefix PATH : ${lib.makeBinPath [ pkgs.docker-compose ]} \
-        ;
-    '';
-  };
-
-  # Unpacked sources for evaluation by `eval`
-  evalSrc' = args.evalSrc or (runCommand "arion-src" {}
-    "mkdir $out; tar -C $out --strip-components=1 -xf ${arion-compose.src}");
-
-  /* Function for evaluating a composition
-
-     Re-uses this Nixpkgs evaluation instead of `arion-pkgs.nix`.
-
-     Returns the module system's `config` and `options` variables.
-   */
-  eval = args@{...}:
-    import (evalSrc' + "/src/nix/eval-composition.nix")
-      ({ inherit pkgs; } // args);
-
-  /* Function to derivation of the docker compose yaml file
-     NOTE: The output will change: https://github.com/hercules-ci/arion/issues/82
-
-     This function is particularly useful on CI.
-   */
-  build = args@{...}:
-    let composition = eval args;
-    in composition.config.out.dockerComposeYaml;
-
-in arion
--- a/nixos-module.nix
+++ b/nixos-module.nix
@ -1,118 +0,0 @@
-{ config, lib, options, pkgs, ... }:
-let
-  inherit (lib)
-    attrValues
-    mkIf
-    mkOption
-    mkMerge
-    types
-    ;
-
-  cfg = config.virtualisation.arion;
-
-  projectType = types.submoduleWith {
-    modules = [ projectModule ];
-  };
-
-  projectModule = { config, name, ... }: {
-    options = {
-      settings = mkOption {
-        description = ''
-          Arion project definition, otherwise known as arion-compose.nix contents.
-
-          See <link xlink:href="https://docs.hercules-ci.com/arion/options/">https://docs.hercules-ci.com/arion/options/</link>.
-        '';
-        type = arionSettingsType name;
-        visible = "shallow";
-      };
-      _systemd = mkOption { internal = true; };
-      serviceName = mkOption {
-        description = "The name of the Arion project's systemd service";
-        type = types.str;
-        default = "arion-${name}";
-      };
-    };
-    config = {
-      _systemd.services.${config.serviceName} = {
-        wantedBy = [ "multi-user.target" ];
-        after = [ "sockets.target" ];
-
-        path = [
-          cfg.package
-          cfg.docker.client.package
-        ];
-        environment.ARION_PREBUILT = config.settings.out.dockerComposeYaml;
-        script = ''
-          echo 1>&2 "docker compose file: $ARION_PREBUILT"
-          arion --prebuilt-file "$ARION_PREBUILT" up
-        '';
-      };
-    };
-  };
-
-  arionSettingsType = name:
-    (cfg.package.eval { modules = [{ project.name = lib.mkDefault name; }]; }).type or (
-      throw "lib.evalModules did not produce a type. Please upgrade Nixpkgs to nixos-unstable or >=nixos-21.11"
-    );
-
-in
-{
-  disabledModules = [ "virtualisation/arion.nix" ];
-
-  options = {
-    virtualisation.arion = {
-      backend = mkOption {
-        type = types.enum [ "podman-socket" "docker" ];
-        description = ''
-          Which container implementation to use.
-        '';
-      };
-      package = mkOption {
-        type = types.package;
-
-        default = (import ./. { inherit pkgs; }).arion;
-        description = ''
-          Arion package to use. This will provide <literal>arion</literal>
-          executable that starts the project.
-
-          It also must provide the arion <literal>eval</literal> function as
-          an attribute.
-        '';
-      };
-      docker.client.package = mkOption {
-        type = types.package;
-        internal = true;
-      };
-      projects = mkOption {
-        type = types.attrsOf projectType;
-        default = { };
-        description = ''
-          Arion projects to be run as a service.
-        '';
-      };
-    };
-  };
-
-  config = mkIf (cfg.projects != { }) (
-    mkMerge [
-      {
-        systemd = mkMerge (map (p: p._systemd) (attrValues cfg.projects));
-      }
-      (mkIf (cfg.backend == "podman-socket") {
-        virtualisation.docker.enable = false;
-        virtualisation.podman.enable = true;
-        virtualisation.podman.dockerSocket.enable = true;
-        virtualisation.podman.defaultNetwork = 
-          if options?virtualisation.podman.defaultNetwork.settings
-          then { settings.dns_enabled = true; } # since 2023-01 https://github.com/NixOS/nixpkgs/pull/199965
-          else { dnsname.enable = true; }; # compat <2023
-
-        virtualisation.arion.docker.client.package = pkgs.docker-client;
-      })
-      (mkIf (cfg.backend == "docker") {
-        virtualisation.docker.enable = true;
-        virtualisation.arion.docker.client.package = pkgs.docker;
-      })
-    ]
-  );
-}
--- a/2
+++ b/2
@ -3,4 +3,4 @@
 # For manual testing of a hacked arion built via Nix.
 # Works when called from outside the project directory.

-exec nix run -f "$(dirname ${BASH_SOURCE[0]})" arion "$@"
+exec nix run -f "$(dirname ${BASH_SOURCE[0]})" arion -c arion "$@"
--- a/shell.nix
+++ b/shell.nix
@ -1 +1 @@
-(builtins.getFlake ("git+file://" + toString ./.)).devShells.${builtins.currentSystem}.default
+args@{...}: (import ./nix args).arion-project.shell
--- a/src/haskell/exe/Main.hs
+++ b/src/haskell/exe/Main.hs
@ -10,7 +10,6 @@ import           Arion.Aeson
 import           Arion.Images (loadImages)
 import qualified Arion.DockerCompose as DockerCompose
 import           Arion.Services (getDefaultExec)
-import           Arion.ExtendedInfo (loadExtendedInfoFromPath, ExtendedInfo(images, projectName))

 import Options.Applicative
 import Control.Monad.Fail
@ -18,7 +17,7 @@ import Control.Monad.Fail
 import qualified Data.Text as T
 import qualified Data.Text.IO as T

-import Data.Aeson(Value)
+import Data.List.NonEmpty (NonEmpty(..))

 import System.Posix.User (getRealUserID)

@ -27,10 +26,6 @@ data CommonOptions =
    { files :: NonEmpty FilePath
    , pkgs :: Text
    , nixArgs :: [Text]
-    , prebuiltComposeFile :: Maybe FilePath
-    , noAnsi :: Bool
-    , compatibility :: Bool
-    , logLevel :: Maybe Text
    }
  deriving (Show)

@ -60,18 +55,9 @@ parseOptions = do
          <> help "Use Nix expression EXPR to get the Nixpkgs attrset used for bootstrapping \
                   \and evaluating the configuration." )
    showTrace <- flag False True (long "show-trace"
-                    <> help "Causes Nix to print out a stack trace in case of Nix expression evaluation errors. Specify before command.")
+                    <> help "Causes Nix to print out a stack trace in case of Nix expression evaluation errors.")
    -- TODO --option support (https://github.com/pcapriotti/optparse-applicative/issues/284)
    userNixArgs <- many (T.pack <$> strOption (long "nix-arg" <> metavar "ARG" <> help "Pass an extra argument to nix. Example: --nix-arg --option --nix-arg substitute --nix-arg false"))
-    prebuiltComposeFile <- optional $ strOption
-               (  long "prebuilt-file"
-               <> metavar "JSONFILE"
-               <> help "Do not evaluate and use the prebuilt JSONFILE instead. Causes other evaluation-related options to be ignored." )
-    noAnsi <- flag False True (long "no-ansi"
-                    <> help "Avoid ANSI control sequences")
-    compatibility <- flag False True (long "no-ansi"
-                    <> help "If set, Docker Compose will attempt to convert deploy keys in v3 files to their non-Swarm equivalent")
-    logLevel <- optional $ fmap T.pack $ strOption (long "log-level" <> metavar "LEVEL" <> help "Set log level (DEBUG, INFO, WARNING, ERROR, CRITICAL)")
    pure $
      let nixArgs = userNixArgs <|> "--show-trace" <$ guard showTrace
      in CommonOptions{..}
@ -151,62 +137,22 @@ runDC cmd (DockerComposeArgs args) _opts = do

 runBuildAndDC :: Text -> DockerComposeArgs -> CommonOptions -> IO ()
 runBuildAndDC cmd dopts opts = do
-  withBuiltComposeFile opts $ callDC cmd dopts opts True
+  ea <- defaultEvaluationArgs opts
+  Arion.Nix.withBuiltComposition ea $ \path -> do
+    loadImages path
+    DockerCompose.run DockerCompose.Args
+      { files = [path]
+      , otherArgs = [cmd] ++ unDockerComposeArgs dopts
+      }

 runEvalAndDC :: Text -> DockerComposeArgs -> CommonOptions -> IO ()
 runEvalAndDC cmd dopts opts = do
-  withComposeFile opts $ callDC cmd dopts opts False
-
-callDC :: Text -> DockerComposeArgs -> CommonOptions -> Bool -> FilePath -> IO ()
-callDC cmd dopts opts shouldLoadImages path = do
-  extendedInfo <- loadExtendedInfoFromPath path
-  when shouldLoadImages $ loadImages (images extendedInfo)
-  let firstOpts = projectArgs extendedInfo <> commonArgs opts
-  DockerCompose.run DockerCompose.Args
-    { files = [path]
-    , otherArgs = firstOpts ++ [cmd] ++ unDockerComposeArgs dopts
-    }
-
-projectArgs :: ExtendedInfo -> [Text]
-projectArgs extendedInfo =
-  do
-    n <- toList (projectName extendedInfo)
-    ["--project-name", n]
-
-commonArgs :: CommonOptions -> [Text]
-commonArgs opts = do
-    guard (noAnsi opts)
-    ["--no-ansi"]
-  <> do
-    guard (compatibility opts)
-    ["--compatibility"]
-  <> do
-    l <- toList (logLevel opts)
-    ["--log-level", l]
-
-withBuiltComposeFile :: CommonOptions -> (FilePath -> IO r) -> IO r
-withBuiltComposeFile opts cont = case prebuiltComposeFile opts of
-  Just prebuilt -> do
-    cont prebuilt
-  Nothing -> do
-    args <- defaultEvaluationArgs opts
-    Arion.Nix.withBuiltComposition args cont
-
-withComposeFile :: CommonOptions -> (FilePath -> IO r) -> IO r
-withComposeFile opts cont = case prebuiltComposeFile opts of
-  Just prebuilt -> do
-    cont prebuilt
-  Nothing -> do
-    args <- defaultEvaluationArgs opts
-    Arion.Nix.withEvaluatedComposition args cont
-
-getComposeValue :: CommonOptions -> IO Value
-getComposeValue opts = case prebuiltComposeFile opts of
-  Just prebuilt -> do
-    decodeFile prebuilt
-  Nothing -> do
-    args <- defaultEvaluationArgs opts
-    Arion.Nix.evaluateComposition args
+  ea <- defaultEvaluationArgs opts
+  Arion.Nix.withEvaluatedComposition ea $ \path ->
+    DockerCompose.run DockerCompose.Args
+      { files = [path]
+      , otherArgs = [cmd] ++ unDockerComposeArgs dopts
+      }

 defaultEvaluationArgs :: CommonOptions -> IO EvaluationArgs
 defaultEvaluationArgs co = do
@ -222,7 +168,7 @@ defaultEvaluationArgs co = do

 runCat :: CommonOptions -> IO ()
 runCat co = do
-  v <- getComposeValue co
+  v <- Arion.Nix.evaluateComposition =<< defaultEvaluationArgs co
  T.hPutStrLn stdout (pretty v)

 runRepl :: CommonOptions -> IO ()
@ -282,18 +228,13 @@ orEmpty' :: (Alternative f, Monoid a) => f a -> f a
 orEmpty' m = fromMaybe mempty <$> optional m

 runExec :: Bool -> Bool -> Maybe Text -> Bool -> Int -> [(Text, Text)] -> Maybe Text -> Text -> [Text] -> CommonOptions -> IO ()
-runExec detach privileged user noTTY index envs workDir service commandAndArgs opts =
-  withComposeFile opts $ \path -> do
-    extendedInfo <- loadExtendedInfoFromPath path
+runExec detach privileged user noTTY index envs workDir service commandAndArgs opts = do
+  putErrText $ "Service: " <> service
+
+  ea <- defaultEvaluationArgs opts
+  Arion.Nix.withEvaluatedComposition ea $ \path -> do
    commandAndArgs'' <- case commandAndArgs of
-      [] -> do
-        cmd <- getDefaultExec path service
-        case cmd of
-          [] -> do
-            putErrText "You must provide a command via service.defaultExec or on the command line."
-            exitFailure
-          _ ->
-            pure cmd
+      [] -> getDefaultExec path service
      x -> pure x
    let commandAndArgs' = case commandAndArgs'' of
          [] -> ["/bin/sh"]
@ -313,7 +254,7 @@ runExec detach privileged user noTTY index envs workDir service commandAndArgs o
          ]
    DockerCompose.run DockerCompose.Args
      { files = [path]
-      , otherArgs = projectArgs extendedInfo <> commonArgs opts <> args
+      , otherArgs = args
      }

 main :: IO ()
--- a/src/haskell/lib/Arion/ExtendedInfo.hs
+++ b/src/haskell/lib/Arion/ExtendedInfo.hs
@ -1,37 +0,0 @@
-{-# LANGUAGE DeriveAnyClass #-}
-{-# LANGUAGE DeriveGeneric #-}
-{-# LANGUAGE OverloadedStrings #-}
-{-
-
-Parses the x-arion field in the generated compose file.
-
-}
-module Arion.ExtendedInfo where
-
-import Prelude()
-import Protolude
-import Data.Aeson as Aeson
-import Arion.Aeson
-import Control.Lens
-import Data.Aeson.Lens
-
-data Image = Image
-  { image :: Maybe Text -- ^ image tar.gz file path
-  , imageExe :: Maybe Text -- ^ path to exe producing image tar
-  , imageName :: Text
-  , imageTag :: Text
-  } deriving (Eq, Show, Generic, Aeson.ToJSON, Aeson.FromJSON)
-
-data ExtendedInfo = ExtendedInfo {
-    projectName :: Maybe Text,
-    images :: [Image]
-  } deriving (Eq, Show)
-
-loadExtendedInfoFromPath :: FilePath -> IO ExtendedInfo
-loadExtendedInfoFromPath fp = do
-  v <- decodeFile fp
-  pure ExtendedInfo {
-    -- TODO: use aeson derived instance?
-    projectName = v ^? key "x-arion" . key "project" . key "name" . _String,
-    images = (v :: Aeson.Value) ^.. key "x-arion" . key "images" . _Array . traverse . _JSON
-  }
--- a/src/haskell/lib/Arion/Images.hs
+++ b/src/haskell/lib/Arion/Images.hs
@ -1,72 +1,60 @@
 {-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE DeriveAnyClass #-}
 {-# LANGUAGE OverloadedStrings #-}
-module Arion.Images
+module Arion.Images 
  ( loadImages
  ) where

 import Prelude()
 import Protolude hiding (to)

+import qualified Data.Aeson as Aeson
+import           Arion.Aeson (decodeFile)
 import qualified System.Process as Process
-import qualified Data.Text as T

-import Arion.ExtendedInfo (Image(..))
+import Control.Lens
+import Data.Aeson.Lens
+import Data.String
+import System.IO (withFile, IOMode(ReadMode))
+
+
+data Image = Image
+  { image :: Text -- ^ file path
+  , imageName :: Text
+  , imageTag :: Text
+  } deriving (Generic, Aeson.ToJSON, Aeson.FromJSON, Show)

 type TaggedImage = Text

 -- | Subject to change
-loadImages :: [Image] -> IO ()
-loadImages requestedImages = do
+loadImages :: FilePath -> IO ()
+loadImages fp = do

-  loaded <- getDockerImages
+  v <- decodeFile fp
+
+  loaded <- dockerImages

  let
-    isNew i =
-      -- On docker, the image name is unmodified
-      (imageName i <> ":" <> imageTag i) `notElem` loaded
-      -- On podman, you used to automatically get a localhost prefix
-      -- however, since NixOS 22.05, this expected to be part of the name instead
-        && ("localhost/" <> imageName i <> ":" <> imageTag i) `notElem` loaded
+    images :: [Image]
+    images = (v :: Aeson.Value) ^.. key "x-arion" . key "images" . _Array . traverse . _JSON

-  traverse_ loadImage . filter isNew $ requestedImages
+    isNew i = (imageName i <> ":" <> imageTag i) `notElem` loaded

-loadImage :: Image -> IO ()
-loadImage Image { image = Just imgPath, imageName = name } =
-  withFile (toS imgPath) ReadMode $ \fileHandle -> do
+  traverse_ loadImage . map (toS . image) . filter isNew $ images
+
+loadImage :: FilePath -> IO ()
+loadImage imgPath = withFile (imgPath) ReadMode $ \fileHandle -> do
  let procSpec = (Process.proc "docker" [ "load" ]) {
          Process.std_in = Process.UseHandle fileHandle
        }
  Process.withCreateProcess procSpec $ \_in _out _err procHandle -> do
-    e <- Process.waitForProcess procHandle
+    e <- Process.waitForProcess procHandle 
    case e of
      ExitSuccess -> pass
-      ExitFailure code ->
-        panic $ "docker load failed with exit code " <> show code <> " for image " <> name <> " from path " <> imgPath
-
-loadImage Image { imageExe = Just imgExe, imageName = name } = do
-  let loadSpec = (Process.proc "docker" [ "load" ]) { Process.std_in = Process.CreatePipe }
-  Process.withCreateProcess loadSpec $ \(Just inHandle) _out _err loadProcHandle -> do
-    let streamSpec = Process.proc (toS imgExe) []
-    Process.withCreateProcess streamSpec { Process.std_out = Process.UseHandle inHandle } $ \_ _ _ streamProcHandle ->
-      withAsync (Process.waitForProcess loadProcHandle) $ \loadExitAsync ->
-        withAsync (Process.waitForProcess streamProcHandle) $ \streamExitAsync -> do
-          r <- waitEither loadExitAsync streamExitAsync
-          case r of
-            Right (ExitFailure code) -> panic $ "image producer for image " <> name <> " failed with exit code " <> show code <> " from executable " <> imgExe
-            Right ExitSuccess -> pass
-            Left _ -> pass
-          loadExit <- wait loadExitAsync
-          case loadExit of
-            ExitFailure code -> panic $ "docker load failed with exit code " <> show code <> " for image " <> name <> " produced by executable " <> imgExe
-            _ -> pass
-          pass
-
-loadImage Image { imageName = name } = do
-  panic $ "image " <> name <> " doesn't specify an image file or imageExe executable"
+      ExitFailure code -> panic $ "docker load (" <> show code <> ") failed for " <> toS imgPath


-getDockerImages :: IO [TaggedImage]
-getDockerImages = do
+dockerImages :: IO [TaggedImage]
+dockerImages = do
  let procSpec = Process.proc "docker" [ "images",  "--filter", "dangling=false", "--format", "{{.Repository}}:{{.Tag}}" ]
-  map toS . T.lines . toS <$> Process.readCreateProcess procSpec ""
+  (map toS . lines) <$> Process.readCreateProcess procSpec ""
--- a/src/haskell/lib/Arion/Nix.hs
+++ b/src/haskell/lib/Arion/Nix.hs
@ -22,6 +22,7 @@ import           Paths_arion_compose
 import qualified Data.Text.IO                  as T

 import qualified Data.List.NonEmpty            as NE
+import           Data.List.NonEmpty             ( NonEmpty(..) )

 import           Control.Arrow                  ( (>>>) )
 import           System.IO.Temp                 ( withTempFile )
--- a/src/haskell/lib/Arion/Services.hs
+++ b/src/haskell/lib/Arion/Services.hs
@ -1,7 +1,6 @@
 {-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE DeriveAnyClass #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE CPP #-}
 module Arion.Services
  ( getDefaultExec
  ) where
@ -10,28 +9,15 @@ import Prelude()
 import Protolude hiding (to)

 import qualified Data.Aeson as Aeson
-#if MIN_VERSION_lens_aeson(1,2,0)
-import qualified Data.Aeson.Key as AK
-#endif
 import           Arion.Aeson (decodeFile)

 import Control.Lens
 import Data.Aeson.Lens

-#if MIN_VERSION_lens_aeson(1,2,0)
-type Key = AK.Key
-mkKey :: Text -> Key
-mkKey = AK.fromText
-#else
-type Key = Text
-mkKey :: Text -> Key
-mkKey = identity
-#endif
-
 -- | Subject to change
 getDefaultExec :: FilePath -> Text -> IO [Text]
 getDefaultExec fp service = do

  v <- decodeFile fp

-  pure ((v :: Aeson.Value) ^.. key "x-arion" . key "serviceInfo" . key (mkKey service) . key "defaultExec" . _Array . traverse . _String)
+  pure ((v :: Aeson.Value) ^.. key "x-arion" . key "serviceInfo" . key service . key "defaultExec" . _Array . traverse . _String)
--- a/src/haskell/test/Arion/NixSpec.hs
+++ b/src/haskell/test/Arion/NixSpec.hs
@ -13,34 +13,19 @@ import qualified Data.Text                     as T
 import qualified Data.Text.IO                  as T

 spec :: Spec
-spec = describe "evaluateComposition" $ do
-  it "matches an example" $ do
-    x <- Arion.Nix.evaluateComposition EvaluationArgs
-      { evalUid      = 123
-      , evalModules  = NEL.fromList
-                         ["src/haskell/testdata/Arion/NixSpec/arion-compose.nix"]
-      , evalPkgs     = "import <nixpkgs> { system = \"x86_64-linux\"; }"
-      , evalWorkDir  = Nothing
-      , evalMode     = ReadOnly
-      , evalUserArgs = ["--show-trace"]
-      }
-    let actual = pretty x
-    expected <- T.readFile "src/haskell/testdata/Arion/NixSpec/arion-compose.json"
-    censorPaths actual `shouldBe` censorPaths expected
-
-  it "matches an build.context example" $ do
-    x <- Arion.Nix.evaluateComposition EvaluationArgs
-      { evalUid      = 1234
-      , evalModules  = NEL.fromList
-                         ["src/haskell/testdata/Arion/NixSpec/arion-context-compose.nix"]
-      , evalPkgs     = "import <nixpkgs> { system = \"x86_64-linux\"; }"
-      , evalWorkDir  = Nothing
-      , evalMode     = ReadOnly
-      , evalUserArgs = ["--show-trace"]
-      }
-    let actual = pretty x
-    expected <- T.readFile "src/haskell/testdata/Arion/NixSpec/arion-context-compose.json"
-    censorPaths actual `shouldBe` censorPaths expected
+spec = describe "evaluateComposition" $ it "matches an example" $ do
+  x <- Arion.Nix.evaluateComposition EvaluationArgs
+    { evalUid      = 123
+    , evalModules  = NEL.fromList
+                       ["src/haskell/testdata/Arion/NixSpec/arion-compose.nix"]
+    , evalPkgs     = "import <nixpkgs> { system = \"x86_64-linux\"; }"
+    , evalWorkDir  = Nothing
+    , evalMode     = ReadOnly
+    , evalUserArgs = ["--show-trace"]
+    }
+  let actual = pretty x
+  expected <- T.readFile "src/haskell/testdata/Arion/NixSpec/arion-compose.json"
+  censorPaths actual `shouldBe` censorPaths expected

 censorPaths :: Text -> Text
 censorPaths = censorImages . censorStorePaths
--- a/src/haskell/test/Spec.hs
+++ b/src/haskell/test/Spec.hs
@ -9,4 +9,3 @@ import qualified Arion.NixSpec
 spec :: Spec
 spec = do
  describe "Arion.Nix" Arion.NixSpec.spec
-
--- a/src/haskell/testdata/Arion/NixSpec/arion-compose.json
+++ b/src/haskell/testdata/Arion/NixSpec/arion-compose.json
@ -1,20 +1,15 @@
 {
-    "networks": {
-        "default": {
-            "name": "unit-test-data"
-        }
-    },
    "services": {
        "webserver": {
            "command": [
-                "/usr/sbin/init"
+                "/nix/store/b9w61w4g8sqgrm3rid6ca22krslqghb3-nixos-system-unnamed-19.03.173100.e726e8291b2/init"
            ],
            "environment": {
                "NIX_REMOTE": "",
                "PATH": "/usr/bin:/run/current-system/sw/bin/",
                "container": "docker"
            },
-            "image": "localhost/webserver:<HASH>",
+            "image": "arion-base:<HASH>",
            "ports": [
                "8000:80"
            ],
@ -28,23 +23,20 @@
            "tty": true,
            "volumes": [
                "/sys/fs/cgroup:/sys/fs/cgroup:ro",
-                "/nix/store:/nix/store:ro"
+                "/nix/store:/nix/store:ro",
+                "/nix/store/pssdmhzjnhflawv7rwk1yw39350iv40g-container-system-env:/run/system:ro"
            ]
        }
    },
    "version": "3.4",
-    "volumes": {},
    "x-arion": {
        "images": [
            {
-                "imageExe": "<STOREPATH>",
-                "imageName": "localhost/webserver",
+                "image": "<STOREPATH>",
+                "imageName": "arion-base",
                "imageTag": "<HASH>"
            }
        ],
-        "project": {
-            "name": "unit-test-data"
-        },
        "serviceInfo": {
            "webserver": {
                "defaultExec": [
--- a/src/haskell/testdata/Arion/NixSpec/arion-compose.nix
+++ b/src/haskell/testdata/Arion/NixSpec/arion-compose.nix
@ -1,8 +1,7 @@
 {
-  project.name = "unit-test-data";
  services.webserver = { pkgs, ... }: {
    nixos.useSystemd = true;
-    nixos.configuration.boot.tmp.useTmpfs = true;
+    nixos.configuration.boot.tmpOnTmpfs = true;
    nixos.configuration.services.nginx.enable = true;
    nixos.configuration.services.nginx.virtualHosts.localhost.root = "${pkgs.nix.doc}/share/doc/nix/manual";
    service.useHostStore = true;
--- a/src/haskell/testdata/Arion/NixSpec/arion-context-compose.json
+++ b/src/haskell/testdata/Arion/NixSpec/arion-context-compose.json
@ -1,41 +0,0 @@
-{
-    "networks": {
-        "default": {
-            "name": "unit-test-data"
-        }
-    },
-    "services": {
-        "webserver": {
-            "build": {
-                "context": "<STOREPATH>"
-            },
-            "environment": {},
-            "ports": [
-                "8080:80"
-            ],
-            "sysctls": {},
-            "volumes": []
-        }
-    },
-    "version": "3.4",
-    "volumes": {},
-    "x-arion": {
-        "images": [
-            {
-                "imageExe": "<STOREPATH>",
-                "imageName": "localhost/webserver",
-                "imageTag": "<HASH>"
-            }
-        ],
-        "project": {
-            "name": "unit-test-data"
-        },
-        "serviceInfo": {
-            "webserver": {
-                "defaultExec": [
-                    "/bin/sh"
-                ]
-            }
-        }
-    }
-}
--- a/src/haskell/testdata/Arion/NixSpec/arion-context-compose.nix
+++ b/src/haskell/testdata/Arion/NixSpec/arion-context-compose.nix
@ -1,9 +0,0 @@
-{
-  project.name = "unit-test-data";
-  services.webserver.service = {
-    build.context = "${./build-context}";
-    ports = [
-      "8080:80"
-    ];
-  };
-}
--- a/src/haskell/testdata/Arion/NixSpec/build-context/Dockerfile
+++ b/src/haskell/testdata/Arion/NixSpec/build-context/Dockerfile
@ -1,4 +0,0 @@
-FROM nginx
-
-RUN echo this is a dockerfile to be built
-
--- a/src/haskell/testdata/docker-compose-example.json
+++ b/src/haskell/testdata/docker-compose-example.json
@ -30,9 +30,6 @@
        "imageTag": "xr4ljmz3qfcwlq9rl4mr4qdrzw93rl70"
      }
    ],
-    "project": {
-      "name": null
-    },
    "serviceInfo": {
      "webserver": {
        "defaultExec": [
--- a/src/nix/eval-composition.nix
+++ b/src/nix/eval-composition.nix
@ -12,6 +12,7 @@ let
  inherit (pkgs) lib;

  composition = lib.evalModules {
+    check = true;
    modules = builtinModules ++ modules;
  };

@ -23,7 +24,6 @@ let
    _file = ./eval-composition.nix;
    key = ./eval-composition.nix;
    config._module.args.pkgs = lib.mkIf (pkgs != null) (lib.mkForce pkgs);
-    config._module.args.check = true;
    config.host.nixStorePrefix = hostNixStorePrefix;
    config.host.uid = lib.toInt uid;
  };
@ -33,5 +33,5 @@ in
  composition // {
    # throw in lib and pkgs for repl convenience
    inherit lib;
-    inherit (composition._module.args) pkgs;
+    inherit (composition.config._module.args) pkgs;
  }
--- a/src/nix/lib.nix
+++ b/src/nix/lib.nix
@ -1,21 +0,0 @@
-{ lib }:
-let
-
-  link = url: text: ''[${text}](${url})'';
-
-  composeSpecRev = "55b450aee50799a2f33cc99e1d714518babe305e";
-
-  serviceRef = fragment:
-    ''See ${link "https://github.com/compose-spec/compose-spec/blob/${composeSpecRev}/05-services.md#${fragment}" "Compose Spec Services #${fragment}"}'';
-
-  networkRef = fragment:
-    ''See ${link "https://github.com/compose-spec/compose-spec/blob/${composeSpecRev}/06-networks.md#${fragment}" "Compose Spec Networks #${fragment}"}'';
-
-in
-{
-  inherit
-    link
-    networkRef
-    serviceRef
-    ;
-}
--- a/src/nix/modules.nix
+++ b/src/nix/modules.nix
@ -2,7 +2,6 @@
    ./modules/composition/docker-compose.nix
    ./modules/composition/host-environment.nix
    ./modules/composition/images.nix
-    ./modules/composition/networks.nix
    ./modules/composition/service-info.nix
-    ./modules/composition/composition.nix
+    ./modules/composition/arion-base-image.nix
 ]
--- a/src/nix/modules/composition/arion-base-image.nix
+++ b/src/nix/modules/composition/arion-base-image.nix
@ -0,0 +1,41 @@
+
+
+# This module is subject to change.
+# In particular, arion-base should use a generic non-service image building system
+
+{ config, lib, pkgs, ... }: 
+
+let
+
+  tag = lib.head (lib.strings.splitString "-" (baseNameOf builtImage.outPath));
+  name = "arion-base";
+
+  builtImage = pkgs.dockerTools.buildLayeredImage {
+    inherit name;
+    contents = pkgs.runCommand "minimal-contents" {} ''
+        mkdir -p $out/bin $out/usr/bin
+        ln -s /run/system/bin/sh $out/bin/sh
+        ln -s /run/system/usr/bin/env $out/usr/bin/env
+      '';
+    config = {};
+  };
+
+in
+
+{
+
+  options = {
+    arionBaseImage = lib.mkOption {
+      type = lib.types.str;
+      description = "Image to use when using useHostStore. Don't use this option yourself. It's going away.";
+      internal = true;
+    };
+  };
+
+  config = {
+    arionBaseImage = "${name}:${tag}";
+    build.imagesToLoad = lib.mkIf (lib.any (s: s.service.useHostStore) (lib.attrValues config.services)) [
+      { image = builtImage; imageName = name; imageTag = tag; }
+    ];  
+  };
+}
--- a/src/nix/modules/composition/composition.nix
+++ b/src/nix/modules/composition/composition.nix
@ -1,28 +0,0 @@
-{ config, lib, ... }:
-let
-  inherit (lib) types mkOption;
-
-  link = url: text:
-    ''[${text}](${url})'';
-
-in
-{
-  options = {
-    _module.args = mkOption {
-      internal = true;
-    };
-    project.name = mkOption {
-      description = ''
-        Name of the project.
-
-        See ${link "https://docs.docker.com/compose/reference/envvars/#compose_project_name" "COMPOSE_PROJECT_NAME"}
-
-        This is not optional, because getting the project name from a directory name tends to produce different results for different repo checkout location names.
-      '';
-      type = types.str;
-    };
-  };
-  config = {
-    docker-compose.extended.project.name = config.project.name;
-  };
-}
--- a/src/nix/modules/composition/docker-compose.nix
+++ b/src/nix/modules/composition/docker-compose.nix
@ -63,11 +63,6 @@ in
      type = lib.types.attrsOf (lib.types.submodule service);
      description = "An attribute set of service configurations. A service specifies how to run an image as a container.";
    };
-    docker-compose.volumes = lib.mkOption {
-      type = lib.types.attrsOf lib.types.unspecified;
-      description = "A attribute set of volume configurations.";
-      default = {};
-    };
  };
  config = {
    out.dockerComposeYaml = pkgs.writeText "docker-compose.yaml" config.out.dockerComposeYamlText;
@ -78,7 +73,6 @@ in
      version = "3.4";
      services = lib.mapAttrs (k: c: c.out.service) config.services;
      x-arion = config.docker-compose.extended;
-      volumes = config.docker-compose.volumes;
    };
  };
 }
--- a/src/nix/modules/composition/host-environment.nix
+++ b/src/nix/modules/composition/host-environment.nix
@ -23,9 +23,9 @@
        stored at an alternate location without altering the format of
        store paths.

-        For example: instead of mounting the host's `/nix/store` as the
-        container's `/nix/store`, this will mount `/mnt/foo/nix/store`
-        as the container's `/nix/store`.
+        For example: instead of mounting the host's /nix/store as the
+        container's /nix/store, this will mount /mnt/foo/nix/store
+        as the container's /nix/store.
      '';
    };

--- a/src/nix/modules/composition/images.nix
+++ b/src/nix/modules/composition/images.nix
@ -16,27 +16,20 @@ let
    (let
      inherit (service) build;
    in {
+      image = build.image.outPath;
      imageName = build.imageName or service.image.name;
      imageTag =
                 if build.image.imageTag != ""
                 then build.image.imageTag
                 else lib.head (lib.strings.splitString "-" (baseNameOf build.image.outPath));
-    } // (if build.image.isExe or false
-        then {
-          imageExe = build.image.outPath;
-        }
-        else {
-          image = build.image.outPath;
-        }
-      )
-    );
+    });
 in
 {
  options = {
    build.imagesToLoad = lib.mkOption {
      type = listOf unspecified;
      internal = true;
-      description = "List of `dockerTools` image derivations.";
+      description = "List of dockerTools image derivations.";
    };
  };
  config = {
--- a/src/nix/modules/composition/networks.nix
+++ b/src/nix/modules/composition/networks.nix
@ -1,53 +0,0 @@
-{ config, lib, ... }:
-
-let
-  inherit (lib)
-    mkOption
-    optionalAttrs
-    types
-    ;
-  inherit (import ../../lib.nix { inherit lib; })
-    link
-    ;
-in
-{
-  options = {
-    networks = mkOption {
-      type = types.lazyAttrsOf (types.submoduleWith {
-        modules = [
-          ../networks/network.nix
-        ];
-      });
-      description = ''
-        See ${link "https://docs.docker.com/compose/compose-file/06-networks/" "Docker Compose Networks"}
-      '';
-    };
-    enableDefaultNetwork = mkOption {
-      type = types.bool;
-      description = ''
-        Whether to define the default network:
-
-        ```nix
-        networks.default = {
-          name = config.project.name;
-        };
-        ```
-      '';
-      default = true;
-    };
-  };
-
-
-  config = {
-
-    networks = optionalAttrs config.enableDefaultNetwork {
-      default = {
-        name = config.project.name;
-      };
-    };
-
-    docker-compose.raw.networks =
-      lib.mapAttrs (k: v: v.out) config.networks;
-
-  };
-}
--- a/src/nix/modules/lib/assert.nix
+++ b/src/nix/modules/lib/assert.nix
@ -3,15 +3,14 @@
 # based on nixpkgs/nixos/modules/system/activation/top-level.nix

 let
-  inherit (lib)
-    concatStringsSep
-    filter
-    mkOption
-    showWarnings
-    types
-    ;
+  inherit (lib) filter concatStringsSep types mkOption;
+
+  # lib.showWarnings since 19.09
+  showWarnings = warnings: res: lib.fold (w: x: lib.warn w x) res warnings;
+  warn = msg: builtins.trace "[1;31mwarning: ${msg}[0m";

  # Handle assertions and warnings
+
  failedAssertions = map (x: x.message) (filter (x: !x.assertion) config.assertions);

  assertWarn = if failedAssertions != []
--- a/src/nix/modules/networks/network.nix
+++ b/src/nix/modules/networks/network.nix
@ -1,131 +0,0 @@
-{ config, lib, options, ... }:
-
-let
-  inherit (lib)
-    mkOption
-    optionalAttrs
-    types
-    ;
-  inherit (import ../../lib.nix { inherit lib; })
-    networkRef
-    ;
-in
-{
-  options = {
-    driver = mkOption {
-      description = ''
-        `"none"`, `"host"`, or a platform-specific value.
-        ${networkRef "driver"}
-      '';
-      type = types.str;
-    };
-
-    driver_opts = mkOption {
-      description = ''
-        ${networkRef "driver_opts"}
-      '';
-      type = types.lazyAttrsOf types.raw or types.unspecified;
-    };
-
-    attachable = mkOption {
-      description = ''
-        ${networkRef "attachable"}
-      '';
-      type = types.bool;
-      example = true;
-    };
-
-    enable_ipv6 = mkOption {
-      description = ''
-        Whether we've entered the 21st century yet.
-        
-        ${networkRef "enable_ipv6"}
-      '';
-      type = types.bool;
-    };
-
-    ipam = mkOption {
-      # TODO model sub-options
-      description = ''
-        Manage IP addresses.
-
-        ${networkRef "ipam"}
-      '';
-      type = types.raw or types.unspecified;
-    };
-
-    internal = mkOption {
-      description = ''
-        Achieves "external isolation".
-
-        ${networkRef "internal"}
-      '';
-      defaultText = false;
-      type = types.bool;
-    };
-
-    labels = mkOption {
-      description = ''
-        Metadata.
-
-        ${networkRef "labels"}
-      '';
-      # no list support, because less expressive wrt overriding
-      type = types.attrsOf types.str;
-    };
-
-    external = mkOption {
-      description = ''
-        When `true`, don't create or destroy the network, but assume that it
-        exists.
-
-        ${networkRef "external"}
-      '';
-      type = types.bool;
-    };
-
-    name = mkOption {
-      description = ''
-        Set a custom name for the network.
-
-        It shares a namespace with other projects' networks. `name` is used as-is.
-
-        Note the `default` network's default `name` is set to `project.name` by Arion.
-
-        ${networkRef "name"}
-      '';
-      type = types.str;
-    };
-
-    out = mkOption {
-      internal = true;
-      description = ''
-        This network's contribution to the docker compose yaml file
-        under the `networks.''${name}` key.
-      '';
-      type = lib.types.attrsOf lib.types.raw or lib.types.unspecified;
-    };
-  };
-
-  config = {
-    out =
-      lib.mapAttrs
-        (k: opt: opt.value)
-        (lib.filterAttrs
-          (k: opt: opt.isDefined)
-          {
-            inherit (options)
-              driver
-              driver_opts
-              attachable
-              enable_ipv6
-              ipam
-              internal
-              labels
-              external
-              name
-              ;
-          }
-        );
-  };
-}
--- a/src/nix/modules/service/all-modules.nix
+++ b/src/nix/modules/service/all-modules.nix
@ -5,9 +5,7 @@
  ./host-store.nix
  ./context.nix
  ./image.nix
-  ./image-recommended.nix
  ./nixos.nix
  ./nixos-init.nix
  ../lib/assert.nix
-  ./check-sys_admin.nix
 ]
--- a/src/nix/modules/service/check-sys_admin.nix
+++ b/src/nix/modules/service/check-sys_admin.nix
@ -1,30 +0,0 @@
-{ config, lib, name, ... }:
-let
-  inherit (lib)
-    concatStringsSep
-    optional
-    ;
-
-  dynamicUserServices = lib.attrNames (
-    lib.filterAttrs
-      (k: v:
-        v.enable &&
-        v.serviceConfig.DynamicUser or false)
-      config.nixos.evaluatedConfig.systemd.services
-    );
-
-  
-in
-{
-  config = {
-    warnings = 
-      optional (config.nixos.useSystemd && !(config.service.capabilities.SYS_ADMIN or false) && dynamicUserServices != []) (
-        ''In service ${name}, the following units require `SYS_ADMIN` capability
-          because of DynamicUser.
-          ${concatStringsSep "\n" (map (srv: "    - services.${name}.nixos.configuration.systemd.services.${srv}") dynamicUserServices)}
-          You can avoid DynamicUser or use
-              services.${name}.service.capabilities.SYS_ADMIN = true;
-        ''
-      );
-  };
-}
--- a/src/nix/modules/service/default-exec.nix
+++ b/src/nix/modules/service/default-exec.nix
@ -9,7 +9,7 @@ in
      default = ["/bin/sh"];
      description = ''
        Container program and arguments to invoke when calling
-        `arion exec <service.name>` without further arguments.
+        <code>arion exec &lt;service.name></code> without further arguments.
      '';
    };
  };
--- a/src/nix/modules/service/docker-compose-service.nix
+++ b/src/nix/modules/service/docker-compose-service.nix
@ -4,16 +4,21 @@
   the user-facing options service.image, service.volumes, etc.

 */
-{ pkgs, lib, config, options, ... }:
+{ pkgs, lib, config, ... }:

 let
  inherit (lib) mkOption types;
-  inherit (types) listOf nullOr attrsOf str either int bool submodule enum;
+  inherit (types) listOf nullOr attrsOf str either int bool;

-  inherit (import ../../lib.nix { inherit lib; })
-    link
-    serviceRef
-    ;
+  link = url: text:
+    ''<link xlink:href="${url}">${text}</link>'';
+  dockerComposeRef = fragment:
+    ''See <link xlink:href="https://docs.docker.com/compose/compose-file/#${fragment}">Docker Compose#${fragment}</link>'';
+  dockerComposeKitchenSink = ''
+    Analogous to the <code>docker run</code> counterpart.
+
+    ${dockerComposeRef "domainname-hostname-ipc-mac_address-privileged-read_only-shm_size-stdin_open-tty-user-working_dir"}
+  '';

  cap_add = lib.attrNames (lib.filterAttrs (name: value: value == true) config.service.capabilities);
  cap_drop = lib.attrNames (lib.filterAttrs (name: value: value == false) config.service.capabilities);
@ -28,7 +33,7 @@ in
    out.service = mkOption {
      type = attrsOf types.unspecified;
      description = ''
-        Raw input for the service in `docker-compose.yaml`.
+        Raw input for the service in <code>docker-compose.yaml</code>.

        You should not need to use this option. If anything is
        missing, please contribute the missing option.
@ -42,7 +47,7 @@ in
    service.name = mkOption {
      type = str;
      description = ''
-        The name of the service - `<name>` in the composition-level `services.<name>`
+        The name of the service - <code>&lt;name></code> in the composition-level <code>services.&lt;name></code>
      '';
      readOnly = true;
    };
@ -50,12 +55,12 @@ in
    service.volumes = mkOption {
      type = listOf types.unspecified;
      default = [];
-      description = serviceRef "volumes";
+      description = dockerComposeRef "volumes";
    };
    service.tmpfs = mkOption {
      type = listOf types.str;
      default = [];
-      description = serviceRef "tmpfs";
+      description = dockerComposeRef "tmpfs";
    };
    service.build.context = mkOption {
      type = nullOr str;
@ -63,193 +68,92 @@ in
      description = ''
        Locates a Dockerfile to use for creating an image to use in this service.

-        https://docs.docker.com/compose/compose-file/build/#context
-      '';
-    };
-    service.build.dockerfile = mkOption {
-      type = nullOr str;
-      default = null;
-      description = ''
-        Sets an alternate Dockerfile. A relative path is resolved from the build context.
-        https://docs.docker.com/compose/compose-file/build/#dockerfile
-      '';
-    };
-    service.build.target = mkOption {
-      type = nullOr str;
-      default = null;
-      description = ''
-        Defines the stage to build as defined inside a multi-stage Dockerfile.
-        https://docs.docker.com/compose/compose-file/build/#target
+        ${dockerComposeRef "context"}
      '';
    };
    service.hostname = mkOption {
      type = nullOr str;
      default = null;
-      description = ''
-        ${serviceRef "hostname"}
-      '';
+      description = dockerComposeKitchenSink;
    };
    service.tty = mkOption {
      type = nullOr bool;
      default = null;
-      description = ''
-        ${serviceRef "tty"}
-      '';
+      description = dockerComposeKitchenSink;
    };
    service.environment = mkOption {
      type = attrsOf (either str int);
      default = {};
-      description = serviceRef "environment";
+      description = dockerComposeRef "environment";
    };
    service.image = mkOption {
-      type = nullOr str;
-      default = null;
-      description = serviceRef "image";
+      type = str;
+      description = dockerComposeRef "image";
    };
    service.command = mkOption {
      type = nullOr types.unspecified;
      default = null;
-      description = serviceRef "command";
+      description = dockerComposeRef "command";
    };
    service.container_name = mkOption {
      type = nullOr types.str;
      default = null;
-      description = serviceRef "container_name";
+      description = dockerComposeRef "container_name";
    };
-    service.depends_on =
-      let conditionsModule = {
-            options = {
-              condition = mkOption {
-                type = enum ["service_started" "service_healthy" "service_completed_successfully"];
-                description = serviceRef "depends_on";
-                default = "service_started";
-              };
-            };
-          };
-       in mkOption {
-         type = either (listOf str) (attrsOf (submodule conditionsModule));
-         default = [];
-         description = serviceRef "depends_on";
-       };
-    service.healthcheck = mkOption {
-      description = serviceRef "healthcheck";
-      type = submodule ({ config, options, ...}: {
-        options = {
-          _out = mkOption {
-            internal = true;
-            default = lib.optionalAttrs (options.test.highestPrio < 1500) {
-              inherit (config) test interval timeout start_period retries;
-            };
-          };
-          test = mkOption {
-            type = nullOr (listOf str);
-            default = null;
-            example = [ "CMD" "pg_isready" ];
-            description = serviceRef "healthcheck";
-          };
-          interval = mkOption {
-            type = str;
-            default = "30s";
-            example = "1m";
-            description = serviceRef "healthcheck";
-          };
-          timeout = mkOption {
-            type = str;
-            default = "30s";
-            example = "10s";
-            description = serviceRef "healthcheck";
-          };
-          start_period = mkOption {
-            type = str;
-            default = "0s";
-            example = "30s";
-            description = serviceRef "healthcheck";
-          };
-          retries = mkOption {
-            type = int;
-            default = 3;
-            description = serviceRef "healthcheck";
-          };
-        };
-      });
+    service.depends_on = mkOption {
+      type = listOf str;
+      default = [];
+      description = dockerComposeRef "depends_on";
    };
    service.devices = mkOption {
      type = listOf str;
      default = [];
      description = ''
        See ${link "https://docs.docker.com/engine/reference/run/#runtime-privilege-and-linux-capabilities"
-        "`docker run --device` documentation"}
+        "<code>docker run --device</code> documentation"}

-        ${serviceRef "devices"}
+        ${dockerComposeRef "devices"}
      '';
    };
-    service.dns = mkOption {
-      type = listOf str;
-      default = [];
-      example = [ "8.8.8.8" "8.8.4.4" ];
-      description = serviceRef "dns";
-    };
-    service.labels = mkOption {
-      type = attrsOf str;
-      default = {};
-      example = {
-        "com.example.foo" = "bar";
-        "traefik.enable" = "true";
-        "traefik.http.routers.my-service.rule" = "Host(`my-service.localhost`)";
-        "traefik.http.routers.my-service.entrypoints" = "web";
-      };
-      description = serviceRef "labels";
-    };
    service.links = mkOption {
      type = listOf str;
      default = [];
-      description = serviceRef "links";
+      description = dockerComposeRef "links";
    };
    service.external_links = mkOption {
      type = listOf str;
      default = [];
-      description = serviceRef "external_links";
-    };
-    service.profiles = mkOption {
-      type = listOf str;
-      default = [];
-      description = serviceRef "profiles";
+      description = dockerComposeRef "external_links";
    };
    service.extra_hosts = mkOption {
      type = listOf str;
      default = [];
-      description = serviceRef "extra_hosts";
+      description = dockerComposeRef "extra_hosts";
    };
    service.working_dir = mkOption {
      type = nullOr str;
      default = null;
-      description = ''
-        ${serviceRef "working_dir"}
-      '';
+      description = dockerComposeKitchenSink;
    };
    service.privileged = mkOption {
      type = nullOr bool;
      default = null;
-      description = ''
-        ${serviceRef "privileged"}
-      '';
+      description = dockerComposeKitchenSink;
    };
    service.entrypoint = mkOption {
      type = nullOr str;
      default = null;
-      description = serviceRef "entrypoint";
+      description = dockerComposeRef "entrypoint";
    };
    service.restart = mkOption {
      type = nullOr str;
      default = null;
-      description = serviceRef "restart";
+      description = dockerComposeRef "restart";
    };
    service.user = mkOption {
      type = nullOr str;
      default = null;
-      description = ''
-        ${serviceRef "user"}
-      '';
+      description = dockerComposeKitchenSink;
    };
    service.ports = mkOption {
      type = listOf types.unspecified;
@ -257,76 +161,38 @@ in
      description = ''
        Expose ports on host. "host:container" or structured.

-        ${serviceRef "ports"}
+        ${dockerComposeRef "ports"}
      '';
    };
    service.expose = mkOption {
      type = listOf str;
      default = [];
-      description = serviceRef "expose";
+      description = dockerComposeRef "expose";
    };
    service.env_file = mkOption {
      type = listOf str;
      default = [];
-      description = serviceRef "env_file";
+      description = dockerComposeRef "env_file";
    };
    service.network_mode = mkOption {
      type = nullOr str;
      default = null;
-      description = serviceRef "network_mode";
+      description = dockerComposeRef "network_mode";
+    };
+    service.networks = mkOption {
+      type = nullOr (listOf types.str);
+      default = null;
+      description = dockerComposeRef "networks";
    };
-    service.networks =
-      let
-        networksModule = submodule ({ config, options, ...}: {
-          options = {
-            _out = mkOption {
-              internal = true;
-              readOnly = true;
-              default = lib.mapAttrs (k: opt: opt.value) (lib.filterAttrs (_: opt: opt.isDefined) { inherit (options) aliases ipv4_address ipv6_address link_local_ips priority; });
-            };
-            aliases = mkOption {
-              type = listOf str;
-              description = serviceRef "aliases";
-              default = [ ];
-            };
-            ipv4_address = mkOption {
-              type = str;
-              description = serviceRef "ipv4_address-ipv6_address";
-            };
-            ipv6_address = mkOption {
-              type = str;
-              description = serviceRef "ipv4_address-ipv6_address";
-            };
-            link_local_ips = mkOption {
-              type = listOf str;
-              description = serviceRef "link_local_ips";
-            };
-            priority = mkOption {
-              type = int;
-              description = serviceRef "priority";
-            };
-          };
-        });
-      in
-      mkOption {
-        type = either (listOf str) (attrsOf networksModule);
-        default = [];
-        description = serviceRef "networks";
-      };
    service.stop_signal = mkOption {
      type = nullOr str;
      default = null;
-      description = serviceRef "stop_signal";
-    };
-    service.stop_grace_period = mkOption {
-      type = nullOr str;
-      default = null;
-      description = serviceRef "stop_grace_period";
+      description = dockerComposeRef "stop_signal";
    };
    service.sysctls = mkOption {
      type = attrsOf (either str int);
      default = {};
-      description = serviceRef "sysctls";
+      description = dockerComposeRef "sysctls";
    };
    service.capabilities = mkOption {
      type = attrsOf (nullOr bool);
@ -335,17 +201,15 @@ in
      description = ''
        Enable/disable linux capabilities, or pick Docker's default.

-        Setting a capability to `true` means that it will be
-        "added". Setting it to `false` means that it will be "dropped".
+        Setting a capability to <code>true</code> means that it will be
+        "added". Setting it to <code>false</code> means that it will be "dropped".
+        ${dockerComposeRef "cap_add-cap_drop"}

-        Omitted and `null` capabilities will therefore be set
+        Omitted and <code>null</code> capabilities will therefore be set
        according to Docker's ${
          link "https://docs.docker.com/engine/reference/run/#runtime-privilege-and-linux-capabilities"
               "default list of capabilities."
        }
-
-        ${serviceRef "cap_add"}
-        ${serviceRef "cap_drop"}
      '';
    };
  };
@ -355,11 +219,10 @@ in
      volumes
      environment
      sysctls
+      image
      ;
-  } // lib.optionalAttrs (config.service.image != null) {
-    inherit (config.service) image;
-  } // lib.optionalAttrs (config.service.build.context != null ) {
-    build = lib.filterAttrs (n: v: v != null)  config.service.build;
+  } // lib.optionalAttrs (config.service.build.context != null) {
+    inherit (config.service) build;
  } // lib.optionalAttrs (cap_add != []) {
    inherit cap_add;
  } // lib.optionalAttrs (cap_drop != []) {
@ -370,8 +233,6 @@ in
    inherit (config.service) container_name;
  } // lib.optionalAttrs (config.service.depends_on != []) {
    inherit (config.service) depends_on;
-  } // lib.optionalAttrs (options.service.healthcheck.highestPrio < 1500) {
-    healthcheck = config.service.healthcheck._out;
  } // lib.optionalAttrs (config.service.devices != []) {
    inherit (config.service) devices;
  } // lib.optionalAttrs (config.service.entrypoint != null) {
@ -386,10 +247,6 @@ in
    inherit (config.service) extra_hosts;
  } // lib.optionalAttrs (config.service.hostname != null) {
    inherit (config.service) hostname;
-  } // lib.optionalAttrs (config.service.dns != []) {
-    inherit (config.service) dns;
-  } // lib.optionalAttrs (config.service.labels != {}) {
-    inherit (config.service) labels;
  } // lib.optionalAttrs (config.service.links != []) {
    inherit (config.service) links;
  } // lib.optionalAttrs (config.service.ports != []) {
@ -398,16 +255,12 @@ in
    inherit (config.service) privileged;
  } // lib.optionalAttrs (config.service.network_mode != null) {
    inherit (config.service) network_mode;
-  } // lib.optionalAttrs (config.service.networks != [] && config.service.networks != {}) {
-    networks =
-      if (builtins.isAttrs config.service.networks) then builtins.mapAttrs (_: v: v._out) config.service.networks
-      else config.service.networks;
+  } // lib.optionalAttrs (config.service.networks != null) {
+    inherit (config.service) networks;
  } // lib.optionalAttrs (config.service.restart != null) {
    inherit (config.service) restart;
  } // lib.optionalAttrs (config.service.stop_signal != null) {
    inherit (config.service) stop_signal;
-  } // lib.optionalAttrs (config.service.stop_grace_period != null) {
-    inherit (config.service) stop_grace_period;
  } // lib.optionalAttrs (config.service.tmpfs != []) {
    inherit (config.service) tmpfs;
  } // lib.optionalAttrs (config.service.tty != null) {
@ -416,7 +269,5 @@ in
    inherit (config.service) working_dir;
  } // lib.optionalAttrs (config.service.user != null) {
    inherit (config.service) user;
-  } // lib.optionalAttrs (config.service.profiles != []) {
-    inherit (config.service) profiles;
  };
 }
--- a/src/nix/modules/service/extended-info.nix
+++ b/src/nix/modules/service/extended-info.nix
@ -12,10 +12,10 @@ in
      type = attrsOf unspecified;
      description = ''
        Information about a service to include in the Docker Compose file,
-        but that will not be used by the `docker-compose` command
+        but that will not be used by the <code>docker-compose</code> command
        itself.

-        It will be inserted in `x-arion.serviceInfo.<service.name>`.
+        It will be inserted in <code>x-arion.serviceInfo.&lt;service.name></code>.
      '';
      default = {};
    };
--- a/src/nix/modules/service/host-store.nix
+++ b/src/nix/modules/service/host-store.nix
@ -20,7 +20,7 @@ in
    service.hostStoreAsReadOnly = mkOption {
      type = types.bool;
      default = true;
-      description = "Adds a `:ro` (read-only) access mode to the host nix store bind mount.";
+      description = "Adds a ':ro' (read-only) access mode to the host nix store bind mount.";
    };
    service.useHostNixDaemon = mkOption {
      type = types.bool;
@ -29,10 +29,12 @@ in
    };
  };
  config = mkIf config.service.useHostStore {
-    image.includeStorePaths = false;
+    image.nixBuild = false; # no need to build and load
+    service.image = config.composition.arionBaseImage;
    service.environment.NIX_REMOTE = lib.optionalString config.service.useHostNixDaemon "daemon";
    service.volumes = [
      "${config.host.nixStorePrefix}/nix/store:/nix/store${lib.optionalString config.service.hostStoreAsReadOnly ":ro"}"
+      "${config.host.nixStorePrefix}${pkgs.buildEnv { name = "container-system-env"; paths = [ pkgs.bashInteractive pkgs.coreutils ]; }}:/run/system${lib.optionalString config.service.hostStoreAsReadOnly ":ro"}"
      ] ++ lib.optional config.service.useHostNixDaemon "/nix/var/nix/daemon-socket:/nix/var/nix/daemon-socket";
    service.command = lib.mkDefault (map escape (config.image.rawConfig.Cmd or []));
  };
--- a/src/nix/modules/service/image-recommended.nix
+++ b/src/nix/modules/service/image-recommended.nix
@ -1,36 +0,0 @@
-{ config, lib, pkgs, ... }:
-let
-  inherit (lib)
-    mkIf
-    mkOption
-    types
-    ;
-  inherit (types)
-    bool
-    ;
-
-  recommendedContents = { runCommand, bash, coreutils }:
-    runCommand "recommended-contents" {} ''
-      mkdir -p $out/bin $out/usr/bin $out/var/empty
-      ln -s ${bash}/bin/sh $out/bin/sh
-      ln -s ${coreutils}/bin/env $out/usr/bin/env
-    '';
-in
-{
-  options = {
-    image.enableRecommendedContents = mkOption {
-      type = bool;
-      default = false;
-      description = ''
-        Add the `/bin/sh` and `/usr/bin/env` symlinks and some lightweight
-        files.
-      '';
-    };
-  };
-
-  config = {
-    image.contents = mkIf config.image.enableRecommendedContents [
-      (pkgs.callPackage recommendedContents {})
-    ];
-  };
-}
--- a/src/nix/modules/service/image.nix
+++ b/src/nix/modules/service/image.nix
@ -1,15 +1,6 @@
 { pkgs, lib, config, options, ... }:
 let
-  inherit (lib)
-    functionArgs
-    mkOption
-    optionalAttrs
-    types
-    warn
-    ;
-  inherit (pkgs)
-    dockerTools
-    ;
+  inherit (lib) types mkOption;
  inherit (types) attrsOf listOf nullOr package str unspecified bool;

  # TODO: dummy-config is a useless layer. Nix 2.3 will let us inspect
@ -18,38 +9,10 @@ let
    (pkgs.writeText "dummy-config.json" (builtins.toJSON config.image.rawConfig))
  ];

-  includeStorePathsWarningAndDefault = lib.warn ''
-    You're using a version of Nixpkgs that doesn't support the includeStorePaths
-    parameter in dockerTools.streamLayeredImage. Without this, Arion's
-    useHostStore does not achieve the intended speedup.
-  '' {};
-
-  buildOrStreamLayeredImage = args:
-    let
-      args_base = builtins.intersectAttrs
-        {
-          name = null; tag = null; contents = null; config = null;
-          created = null; extraCommands = null; maxLayers = null;
-          fakeRootCommands = null;
-        }
-        args;
-      acceptedArgs = functionArgs dockerTools.streamLayeredImage;
-      args_no_store = lib.optionalAttrs (!(args.includeStorePaths or true)) (
-        if acceptedArgs ? includeStorePaths
-        then { inherit (args) includeStorePaths; }
-        else includeStorePathsWarningAndDefault
-      );
-      args_streamLayered = args_base // args_no_store;
-    in
-      if dockerTools?streamLayeredImage
-      then dockerTools.streamLayeredImage args_streamLayered // { isExe = true; }
-      else dockerTools.buildLayeredImage args_base;
-
-  builtImage = buildOrStreamLayeredImage {
+  builtImage = pkgs.dockerTools.buildLayeredImage {
    inherit (config.image)
      name
      contents
-      includeStorePaths
      ;
    config = config.image.rawConfig;
    maxLayers = 100;
@ -68,8 +31,6 @@ let
          ln -s $i nix/var/nix/gcroots/docker/$(basename $i)
        done;
      '';
-
-    fakeRootCommands = config.image.fakeRootCommands;
  };

  priorityIsDefault = option: option.highestPrio >= (lib.mkDefault true).priority;
@ -79,41 +40,41 @@ in
    build.image = mkOption {
      type = nullOr package;
      description = ''
-        Docker image derivation to be `docker load`-ed.
+        Docker image derivation to be <code>docker load</code>ed.
      '';
      internal = true;
    };
    build.imageName = mkOption {
      type = str;
-      description = "Derived from `build.image`";
+      description = "Derived from build.image";
      internal = true;
    };
    build.imageTag = mkOption {
      type = str;
-      description = "Derived from `build.image`";
+      description = "Derived from build.image";
      internal = true;
    };
    image.nixBuild = mkOption {
      type = bool;
      description = ''
        Whether to build this image with Nixpkgs'
-        `dockerTools.buildLayeredImage`
-        and then load it with `docker load`.
+        <code>dockerTools.buildLayeredImage</code>
+        and then load it with <code>docker load</code>.

-        By default, an image will be built with Nix unless `service.image`
-        is set. See also `image.name`, which defaults to
+        By default, an image will be built with Nix unless <option>service.image</option>
+        is set. See also <option>image.name</option>, which defaults to
        the service name.
      '';
    };
    image.name = mkOption {
      type = str;
-      default = "localhost/" + config.service.name;
-      defaultText = lib.literalExpression or lib.literalExample ''"localhost/" + config.service.name'';
+      default = config.service.name;
+      defaultText = lib.literalExample "config.service.name";
      description = ''
        A human readable name for the docker image.

-        Shows up in the `docker ps` output in the
-        `IMAGE` column, among other places.
+        Shows up in the <code>docker ps</code> output in the
+        <code>IMAGE</code> column, among other places.
      '';
    };
    image.contents = mkOption {
@ -123,24 +84,6 @@ in
         Top level paths in the container.
      '';
    };
-    image.fakeRootCommands = mkOption {
-      type = types.lines;
-      default = "";
-      description = ''
-        Commands that build the root of the container in the current working directory.
-
-        See [`dockerTools.buildLayeredImage`](https://nixos.org/manual/nixpkgs/stable/#ssec-pkgs-dockerTools-buildLayeredImage).
-      '';
-    };
-    image.includeStorePaths = mkOption {
-      type = bool;
-      default = true;
-      internal = true;
-      description = ''
-        Include all referenced store paths. You generally want this in your
-        image, unless you load store paths via some other means, like `useHostStore = true`;
-      '';
-    };
    image.rawConfig = mkOption {
      type = attrsOf unspecified;
      default = {};
@ -149,11 +92,11 @@ in
        been modeled in the Arion module system.

        This attribute set does not have an appropriate merge function.
-        Please use the specific `image` options instead.
+        Please use the specific <code>image</code> options instead.

        Run-time configuration of the container. A full list of the
-        options is available in the [Docker Image Specification
-        v1.2.0](https://github.com/moby/moby/blob/master/image/spec/v1.2.md#image-json-field-descriptions).
+        options are available at in the <link xlink:href="https://github.com/moby/moby/blob/master/image/spec/v1.2.md#image-json-field-descriptions">Docker Image Specification
+        v1.2.0</link>.
      '';
    };
    image.command = mkOption {
@ -163,19 +106,17 @@ in
      '';
    };
  };
-  config = lib.mkMerge [{
-      build.image = builtImage;
-      build.imageName = config.build.image.imageName;
-      build.imageTag =
-                   if config.build.image.imageTag != ""
-                   then config.build.image.imageTag
-                   else lib.head (lib.strings.splitString "-" (baseNameOf config.build.image.outPath));
-      image.rawConfig.Cmd = config.image.command;
-      image.nixBuild = lib.mkDefault (priorityIsDefault options.service.image);
-    }
-    ( lib.mkIf (config.service.build.context == null)
-    {
-      service.image = lib.mkDefault "${config.build.imageName}:${config.build.imageTag}";
-    })
-  ];
+  config = {
+    build.image = builtImage;
+    build.imageName = config.build.image.imageName;
+    build.imageTag =
+                 if config.build.image.imageTag != ""
+                 then config.build.image.imageTag
+                 else lib.head (lib.strings.splitString "-" (baseNameOf config.build.image.outPath));
+
+    service.image = lib.mkDefault "${config.build.imageName}:${config.build.imageTag}";
+    image.rawConfig.Cmd = config.image.command;
+
+    image.nixBuild = lib.mkDefault (priorityIsDefault options.service.image);
+  };
 }
--- a/src/nix/modules/service/nixos-init.nix
+++ b/src/nix/modules/service/nixos-init.nix
@ -13,7 +13,7 @@ in
      description = ''
        When enabled, call the NixOS systemd-based init system.

-        Configure NixOS with the `nixos.configuration` option.
+        Configure NixOS with <code>nixos.configuration</code>.
      '';
    };
  };
@ -24,13 +24,7 @@ in
      ../nixos/default-shell.nix
      (pkgs.path + "/nixos/modules/profiles/minimal.nix")
    ];
-    image.command = [ "/usr/sbin/init" ];
-    image.contents = [
-      (pkgs.runCommand "root-init" {} ''
-        mkdir -p $out/usr/sbin
-        ln -s ${config.nixos.build.toplevel}/init $out/usr/sbin/init
-      '')
-    ];
+    image.command = [ "${config.nixos.build.toplevel}/init" ];
    service.environment.container = "docker";
    service.environment.PATH = "/usr/bin:/run/current-system/sw/bin/";
    service.volumes = [
@ -39,7 +33,7 @@ in
    service.tmpfs = [
      "/run"          # noexec is fine because exes should be symlinked from elsewhere anyway
      "/run/wrappers" # noexec breaks this intentionally
-    ] ++ lib.optional (config.nixos.evaluatedConfig.boot.tmp.useTmpfs) "/tmp:exec,mode=777";
+    ] ++ lib.optional (config.nixos.evaluatedConfig.boot.tmpOnTmpfs) "/tmp:exec,mode=777";

    service.stop_signal = "SIGRTMIN+3";
    service.tty = true;
--- a/src/nix/modules/service/nixos.nix
+++ b/src/nix/modules/service/nixos.nix
@ -18,7 +18,7 @@ in

        This option is unused by default, because not all images use NixOS.

-        One way to use this is to enable `nixos.useSystemd`, but the
+        One way to use this is to enable <code>nixos.useSystemd</code>, but the
        NixOS configuration can be used in other ways.
      '';
    };
@ -27,11 +27,11 @@ in
      type = attrs;
      readOnly = true;
      description = ''
-        NixOS build products from `config.system.build`, such as `toplevel` and `etc`.
+        NixOS build products from <code>config.system.build</code>, such as <code>toplevel</code> and <code>etc</code>.

        This option is unused by default, because not all images use NixOS.

-        One way to use this is to enable `nixos.useSystemd`, but the
+        One way to use this is to enable <code>nixos.useSystemd</code>, but the
        NixOS configuration can be used in other ways.
      '';
    };
@ -44,7 +44,7 @@ in

        This option is unused by default, because not all images use NixOS.

-        One way to use this is to enable `nixos.useSystemd`, but the
+        One way to use this is to enable <code>nixos.useSystemd</code>, but the
        NixOS configuration can be used in other ways.
      '';
    };
--- a/tests/arion-test/default.nix
+++ b/tests/arion-test/default.nix
@ -1,4 +1,4 @@
-{ usePodman ? false, pkgs, lib ? pkgs.lib, ... }:
+{ pkgs, ... }:

 let
  # To make some prebuilt derivations available in the vm
@ -6,168 +6,61 @@ let
    inherit modules;
    inherit pkgs;
  };
-
-  inherit (lib)
-    concatMapStringsSep
-    optionalAttrs
-    optionalString
-    ;
-
-  haveSystemd = usePodman || pkgs.arionTestingFlags.dockerSupportsSystemd;
-
-  concatPathLines = paths: concatMapStringsSep "\n" (x: "${x}") paths;
-
 in
 {
  name = "arion-test";
-  nodes.machine = { pkgs, lib, ... }: {
+  machine = { pkgs, lib, ... }: {
    environment.systemPackages = [
      pkgs.arion
-    ] ++ lib.optional usePodman pkgs.docker;
-    virtualisation.docker.enable = !usePodman;
-    virtualisation.podman = optionalAttrs usePodman {
-      enable = true;
-      dockerSocket.enable = true;
-    };
-
+    ];
+    virtualisation.docker.enable = true;
+    
    # no caches, because no internet
-    nix.settings.substituters = lib.mkForce [];
+    nix.binaryCaches = lib.mkForce [];
+
+    # FIXME: Sandbox seems broken with current version of NixOS test
+    #        w/ writable store. Error:
+    #        machine# error: linking '/nix/store/7r8z2zvhwda85pgpdn5hzzz6hs1njklc-stdenv-linux.drv.chroot/nix/store/6v3y7s4q4wd16hsw393gjpxvcf9159bv-patch-shebangs.sh' to '/nix/store/6v3y7s4q4wd16hsw393gjpxvcf9159bv-patch-shebangs.sh': Operation not permitted
+    #
+    #        There should be no reason why arion can't run without
+    #        sandboxing, so please re-enable.
+    nix.useSandbox = false;

    virtualisation.writableStore = true;
-    # Switch to virtualisation.additionalPaths when dropping all NixOS <= 21.05.
-    environment.etc."extra-paths-for-test".text = concatPathLines [
+    virtualisation.pathsInNixDB = [
      # Pre-build the image because we don't want to build the world
      # in the vm.
      (preEval [ ../../examples/minimal/arion-compose.nix ]).config.out.dockerComposeYaml
      (preEval [ ../../examples/full-nixos/arion-compose.nix ]).config.out.dockerComposeYaml
      (preEval [ ../../examples/nixos-unit/arion-compose.nix ]).config.out.dockerComposeYaml
-      (preEval [ ../../examples/traefik/arion-compose.nix ]).config.out.dockerComposeYaml
      pkgs.stdenv
    ];
-
-    virtualisation.memorySize = 2048;
-    virtualisation.diskSize = 8000;
  };
  testScript = ''
-    machine.fail("curl --fail localhost:8000")
-    machine.succeed("docker --version")
+    $machine->fail("curl localhost:8000");
+    $machine->succeed("docker --version");

-    # Tests
-    #  - arion up
-    #  - arion down
-    #  - examples/minimal
-    with subtest("minimal"):
-        machine.succeed(
-            "rm -rf work && cp -frT ${../../examples/minimal} work && cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion up -d"
-        )
-        machine.wait_until_succeeds("curl --fail localhost:8000")
-        machine.succeed(
-            "cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion down"
-        )
-        machine.wait_until_fails("curl --fail localhost:8000")
+    subtest "minimal", sub {
+      $machine->succeed("cp -r ${../../examples/minimal} work && cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion up -d");
+      $machine->waitUntilSucceeds("curl localhost:8000");
+      $machine->succeed("cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion down && rm -rf work");
+      $machine->waitUntilFails("curl localhost:8000");
+    };

-    # Tests
-    #  - running same image again doesn't require a `docker load`
-    with subtest("docker load only once"):
-        # We assume image loading relies on the `docker images` and `docker load` commands, so this should fail
-        machine.fail(
-            "export REAL_DOCKER=$(which docker); rm -rf work && cp -frT ${../../examples/minimal} work && cd work && NIX_PATH=nixpkgs='${pkgs.path}' PATH=\"${pkgs.writeScriptBin "docker" ''
-              #!${pkgs.runtimeShell} -eu
-              echo 1>&2 "This failure is expected. Args were" "$@"
-              echo "$@" >/tmp/docker-args
-              exit 1
-            ''}/bin:$PATH\" arion up -d"
-        )
-        machine.succeed(
-            "export REAL_DOCKER=$(which docker); rm -rf work && cp -frT ${../../examples/minimal} work && cd work && NIX_PATH=nixpkgs='${pkgs.path}' PATH=\"${pkgs.writeScriptBin "docker" ''
-              #!${pkgs.runtimeShell} -eu
-              case $1 in
-                load)
-                  echo 1>&2 "arion must not docker load when upping the same deployment for the second time"
-                  exit 1
-                  ;;
-                images)
-                  echo 1>&2 "execing docker to list images"
-                  exec $REAL_DOCKER "$@"
-                  ;;
-                *)
-                  echo 1>&2 "Unknown docker invocation. This may be a shortcoming of this docker mock."
-                  echo 1>&2 "Invocation: docker" "$@"
-                  ;;
-              esac
-            ''}/bin:$PATH\" arion up -d"
-        )
-        machine.wait_until_succeeds("curl --fail localhost:8000")
-        machine.succeed(
-            "cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion down"
-        )
-        machine.wait_until_fails("curl --fail localhost:8000")
+    subtest "full-nixos", sub {
+      $machine->succeed("cp -r ${../../examples/full-nixos} work && cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion up -d");
+      $machine->waitUntilSucceeds("curl localhost:8000");
+      # Also test exec with defaultExec
+      $machine->succeed("cd work && export NIX_PATH=nixpkgs='${pkgs.path}' && (echo 'nix run -f ~/h/arion arion -c arion exec webserver'; echo 'target=world; echo Hello \$target'; echo exit) | script /dev/null | grep 'Hello world'");
+      $machine->succeed("cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion down && rm -rf work");
+      $machine->waitUntilFails("curl localhost:8000");
+    };

-
-    # Tests
-    #  - examples/flake
-    # This _test_ doesn't work because flake-compat fetches the github
-    # tarballs without sha256 and/or Nix doesn't consult the store before
-    # downloading.
-    # See https://github.com/edolstra/flake-compat/pull/12
-    # with subtest("flake"):
-    #     machine.succeed(
-    #         "rm -rf work && cp -frT ''${../../examples/flake} work && cd work && NIX_PATH= arion up -d"
-    #     )
-    #     machine.wait_until_succeeds("curl --fail localhost:8000")
-    #     machine.succeed("cd work && NIX_PATH= arion down")
-    #     machine.wait_until_fails("curl --fail localhost:8000")
-
-    ${optionalString haveSystemd ''
-    # Tests
-    #  - arion exec
-    #  - examples/full-nixos
-    with subtest("full-nixos"):
-        machine.succeed(
-            "rm -rf work && cp -frT ${../../examples/full-nixos} work && cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion up -d"
-        )
-        machine.wait_until_succeeds("curl --fail localhost:8000")
-
-        machine.succeed(
-            """
-            set -eux -o pipefail
-            cd work
-            export NIX_PATH=nixpkgs='${pkgs.path}'
-            echo 'target=world; echo Hello $target; exit' \
-              | script 'arion exec webserver' \
-              | grep 'Hello world'
-            """
-        ),
-
-        machine.succeed(
-            "cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion down"
-        )
-        machine.wait_until_fails("curl --fail localhost:8000")
-    ''}
-
-    # Tests
-    #  - examples/nixos-unit
-    with subtest("nixos-unit"):
-        machine.succeed(
-            "rm -rf work && cp -frT ${../../examples/nixos-unit} work && cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion up -d"
-        )
-        machine.wait_until_succeeds("curl --fail localhost:8000")
-        machine.succeed(
-            "cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion down"
-        )
-        machine.wait_until_fails("curl --fail localhost:8000")
-
-    # Tests
-    # - examples/traefik
-    # - labels
-    with subtest("traefik"):
-        machine.succeed(
-            "rm -rf work && cp -frT ${../../examples/traefik} work && cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion up -d"
-        )
-        machine.wait_until_succeeds("curl --fail nix-docs.localhost")
-        machine.succeed(
-            "cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion down"
-        )
-        machine.wait_until_fails("curl --fail nix-docs.localhost")
+    subtest "nixos-unit", sub {
+      $machine->succeed("cp -r ${../../examples/nixos-unit} work && cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion up -d");
+      $machine->waitUntilSucceeds("curl localhost:8000");
+      $machine->succeed("cd work && NIX_PATH=nixpkgs='${pkgs.path}' arion down && rm -rf work");
+      $machine->waitUntilFails("curl localhost:8000");
+    };
  '';
 }
--- a/tests/default.nix
+++ b/tests/default.nix
@ -0,0 +1,20 @@
+{ pkgs ? import ../pkgs.nix }:
+let
+  inherit (pkgs) nixosTest recurseIntoAttrs arion;
+in
+
+recurseIntoAttrs {
+
+  test = nixosTest ./arion-test;
+
+  testBuild = arion.build {
+
+    # To be more accurately, you can do
+    #   pkgs = import ../examples/minimal/arion-pkgs.nix;
+    # but this is quite efficient:
+    inherit pkgs;
+
+    modules = [ ../examples/minimal/arion-compose.nix ];
+  };
+
+}
--- a/tests/flake-module.nix
+++ b/tests/flake-module.nix
@ -1,36 +0,0 @@
-{
-  perSystem = { pkgs, final, ... }:
-    let
-      inherit (final) nixosTest arion lib;
-    in
-    {
-      checks = lib.optionalAttrs pkgs.stdenv.isLinux {
-        test = nixosTest ./arion-test;
-
-        nixosModuleWithDocker =
-          import ./nixos-virtualization-arion-test/test.nix final {
-            virtualisation.arion.backend = "docker";
-          };
-
-        # Currently broken; kafka can't reach zookeeper
-        # nixosModuleWithPodman =
-        #   import ./nixos-virtualization-arion-test/test.nix final {
-        #     virtualisation.arion.backend = "podman-socket";
-        #   };
-
-        testWithPodman =
-          nixosTest (import ./arion-test { usePodman = true; pkgs = final; });
-
-        testBuild = arion.build {
-
-          # To be more accurate, we could do
-          #   pkgs = import ../examples/minimal/arion-pkgs.nix;
-          # But let's avoid re-evaluating Nixpkgs
-          pkgs = final;
-
-          modules = [ ../examples/minimal/arion-compose.nix ];
-        };
-
-      };
-    };
-}
--- a/tests/nixos-virtualization-arion-test/README.md
+++ b/tests/nixos-virtualization-arion-test/README.md
@ -1,6 +0,0 @@
-
-# NixOS module test
-
-This tests the NixOS module.
-
-The images used here are experimental and not meant for production.
--- a/tests/nixos-virtualization-arion-test/arion-compose.nix
+++ b/tests/nixos-virtualization-arion-test/arion-compose.nix
@ -1,62 +0,0 @@
-{ pkgs, ... }: {
-  project.name = "whale";
-
-  docker-compose.raw = {
-    volumes.zookeeper = { };
-    volumes.kafka = { };
-  };
-
-  services.kafka = {
-    service.useHostStore = true;
-    # service.volumes = [
-    #   {
-    #     type = "volume";
-    #     source = "kafka";
-    #     target = "/data";
-    #     # volume.nocopy = true;
-    #   }
-    # ];
-    service.ports = [ "9092:9092" ];
-    service.depends_on = [ "zookeeper" ];
-    image.name = "localhost/kafka";
-    image.contents = [
-      (pkgs.runCommand "root" { } ''
-        mkdir -p $out/bin
-        ln -s ${pkgs.runtimeShell} $out/bin/sh
-      '')
-    ];
-    image.command = [
-      "${pkgs.apacheKafka}/bin/kafka-server-start.sh"
-      "${./kafka/server.properties}"
-    ];
-  };
-
-  services.zookeeper = {
-    service.useHostStore = true;
-    service.ports = [ "2181:2181" ];
-    # service.volumes = [
-    #   {
-    #     type = "volume";
-    #     source = "zookeeper";
-    #     target = "/data";
-    #     # volume.nocopy = true;
-    #   }
-    # ];
-    image.name = "localhost/zookeeper";
-    image.contents = [
-      (pkgs.buildEnv {
-        name = "root";
-        paths = [
-          # pkgs.sed
-          pkgs.busybox
-        ];
-      })
-    ];
-    image.command = [
-      "${pkgs.zookeeper}/bin/zkServer.sh"
-      "--config"
-      "${./zookeeper}"
-      "start-foreground"
-    ];
-  };
-}
--- a/tests/nixos-virtualization-arion-test/arion-pkgs.nix
+++ b/tests/nixos-virtualization-arion-test/arion-pkgs.nix
@ -1,6 +0,0 @@
-# NOTE: This isn't used in the module!
-import <nixpkgs> {
-  # We specify the architecture explicitly. Use a Linux remote builder when
-  # calling arion from other platforms.
-  system = "x86_64-linux";
-}
--- a/tests/nixos-virtualization-arion-test/kafka/server.properties
+++ b/tests/nixos-virtualization-arion-test/kafka/server.properties
@ -1,141 +0,0 @@
-# Licensed to the Apache Software Foundation (ASF) under one or more
-# contributor license agreements.  See the NOTICE file distributed with
-# this work for additional information regarding copyright ownership.
-# The ASF licenses this file to You under the Apache License, Version 2.0
-# (the "License"); you may not use this file except in compliance with
-# the License.  You may obtain a copy of the License at
-#
-#    http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-# see kafka.server.KafkaConfig for additional details and defaults
-
-############################# Server Basics #############################
-
-# The id of the broker. This must be set to a unique integer for each broker.
-broker.id=0
-
-############################# Socket Server Settings #############################
-
-# The address the socket server listens on. It will get the value returned from 
-# java.net.InetAddress.getCanonicalHostName() if not configured.
-#   FORMAT:
-#     listeners = listener_name://host_name:port
-#   EXAMPLE:
-#     listeners = PLAINTEXT://your.host.name:9092
-listeners=LOCALHOST://0.0.0.0:9092,SERVICE://kafka:9093
-
-# Hostname and port the broker will advertise to producers and consumers. If not set, 
-# it uses the value for "listeners" if configured.  Otherwise, it will use the value
-# returned from java.net.InetAddress.getCanonicalHostName().
-# advertised.listeners=PLAINTEXT://whale_kafka_1:9092
-advertised.listeners=LOCALHOST://localhost:9092,SERVICE://kafka:9093
-
-# ???
-inter.broker.listener.name=LOCALHOST
-
-# Maps listener names to security protocols, the default is for them to be the same. See the config documentation for more details
-#listener.security.protocol.map=PLAINTEXT:PLAINTEXT,SSL:SSL,SASL_PLAINTEXT:SASL_PLAINTEXT,SASL_SSL:SASL_SSL
-listener.security.protocol.map=LOCALHOST:PLAINTEXT,SERVICE:PLAINTEXT
-
-# The number of threads that the server uses for receiving requests from the network and sending responses to the network
-num.network.threads=3
-
-# The number of threads that the server uses for processing requests, which may include disk I/O
-num.io.threads=8
-
-# The send buffer (SO_SNDBUF) used by the socket server
-socket.send.buffer.bytes=102400
-
-# The receive buffer (SO_RCVBUF) used by the socket server
-socket.receive.buffer.bytes=102400
-
-# The maximum size of a request that the socket server will accept (protection against OOM)
-socket.request.max.bytes=104857600
-
-
-############################# Log Basics #############################
-
-# A comma separated list of directories under which to store log files
-log.dirs=/data/kafka
-
-# The default number of log partitions per topic. More partitions allow greater
-# parallelism for consumption, but this will also result in more files across
-# the brokers.
-num.partitions=1
-
-# The number of threads per data directory to be used for log recovery at startup and flushing at shutdown.
-# This value is recommended to be increased for installations with data dirs located in RAID array.
-num.recovery.threads.per.data.dir=1
-
-############################# Internal Topic Settings  #############################
-# The replication factor for the group metadata internal topics "__consumer_offsets" and "__transaction_state"
-# For anything other than development testing, a value greater than 1 is recommended to ensure availability such as 3.
-offsets.topic.replication.factor=1
-transaction.state.log.replication.factor=1
-transaction.state.log.min.isr=1
-
-############################# Log Flush Policy #############################
-
-# Messages are immediately written to the filesystem but by default we only fsync() to sync
-# the OS cache lazily. The following configurations control the flush of data to disk.
-# There are a few important trade-offs here:
-#    1. Durability: Unflushed data may be lost if you are not using replication.
-#    2. Latency: Very large flush intervals may lead to latency spikes when the flush does occur as there will be a lot of data to flush.
-#    3. Throughput: The flush is generally the most expensive operation, and a small flush interval may lead to excessive seeks.
-# The settings below allow one to configure the flush policy to flush data after a period of time or
-# every N messages (or both). This can be done globally and overridden on a per-topic basis.
-
-# The number of messages to accept before forcing a flush of data to disk
-#log.flush.interval.messages=10000
-
-# The maximum amount of time a message can sit in a log before we force a flush
-#log.flush.interval.ms=1000
-
-############################# Log Retention Policy #############################
-
-# The following configurations control the disposal of log segments. The policy can
-# be set to delete segments after a period of time, or after a given size has accumulated.
-# A segment will be deleted whenever *either* of these criteria are met. Deletion always happens
-# from the end of the log.
-
-# The minimum age of a log file to be eligible for deletion due to age
-log.retention.hours=168
-
-# A size-based retention policy for logs. Segments are pruned from the log unless the remaining
-# segments drop below log.retention.bytes. Functions independently of log.retention.hours.
-#log.retention.bytes=1073741824
-
-# The maximum size of a log segment file. When this size is reached a new log segment will be created.
-log.segment.bytes=1073741824
-
-# The interval at which log segments are checked to see if they can be deleted according
-# to the retention policies
-log.retention.check.interval.ms=300000
-
-############################# Zookeeper #############################
-
-# Zookeeper connection string (see zookeeper docs for details).
-# This is a comma separated host:port pairs, each corresponding to a zk
-# server. e.g. "127.0.0.1:3000,127.0.0.1:3001,127.0.0.1:3002".
-# You can also append an optional chroot string to the urls to specify the
-# root directory for all kafka znodes.
-zookeeper.connect=zookeeper:2181
-
-# Timeout in ms for connecting to zookeeper
-zookeeper.connection.timeout.ms=18000
-
-
-############################# Group Coordinator Settings #############################
-
-# The following configuration specifies the time, in milliseconds, that the GroupCoordinator will delay the initial consumer rebalance.
-# The rebalance will be further delayed by the value of group.initial.rebalance.delay.ms as new members join the group, up to a maximum of max.poll.interval.ms.
-# The default value for this is 3 seconds.
-# We override this to 0 here as it makes for a better out-of-the-box experience for development and testing.
-# However, in production environments the default value of 3 seconds is more suitable as this will help to avoid unnecessary, and potentially expensive, rebalances during application startup.
-group.initial.rebalance.delay.ms=0
--- a/tests/nixos-virtualization-arion-test/test.nix
+++ b/tests/nixos-virtualization-arion-test/test.nix
@ -1,40 +0,0 @@
-pkgs: module:
-
-pkgs.nixosTest {
-  name = "test-basic-arion-kafka";
-  nodes = {
-    machine = { ... }: {
-      virtualisation.memorySize = 4096;
-      virtualisation.diskSize = 10000;
-      imports = [
-        ../../nixos-module.nix
-        module
-      ];
-
-      virtualisation.arion.projects.whale.settings = {
-        imports = [ ./arion-compose.nix ];
-      };
-    };
-  };
-  testScript = ''
-    machine.wait_for_unit("sockets.target")
-    machine.wait_for_unit("arion-whale.service")
-
-    machine.succeed("""
-      (echo "hello"; echo "world") \
-        | ${pkgs.apacheKafka}/bin/kafka-console-producer.sh \
-            --topic thetopic --bootstrap-server localhost:9092
-    """)
-
-    machine.succeed("""
-      (
-        set +o pipefail  # we only care for head's exit code
-        ( ${pkgs.apacheKafka}/bin/kafka-console-consumer.sh \
-            --topic thetopic --from-beginning --bootstrap-server localhost:9092 & \
-          echo $! >pid
-        ) | grep --line-buffered hello | { read; kill $(<pid); rm pid; }
-      ) 2>/dev/console
-    """)
-    
-  '';
-}
--- a/tests/nixos-virtualization-arion-test/zookeeper/log4j.properties
+++ b/tests/nixos-virtualization-arion-test/zookeeper/log4j.properties
@ -1,82 +0,0 @@
-# Copyright 2012 The Apache Software Foundation
-# 
-# Licensed to the Apache Software Foundation (ASF) under one
-# or more contributor license agreements.  See the NOTICE file
-# distributed with this work for additional information
-# regarding copyright ownership.  The ASF licenses this file
-# to you under the Apache License, Version 2.0 (the
-# "License"); you may not use this file except in compliance
-# with the License.  You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-# Define some default values that can be overridden by system properties
-zookeeper.root.logger=INFO, CONSOLE
-
-zookeeper.console.threshold=INFO
-
-zookeeper.log.dir=.
-zookeeper.log.file=zookeeper.log
-zookeeper.log.threshold=INFO
-zookeeper.log.maxfilesize=256MB
-zookeeper.log.maxbackupindex=20
-
-# zookeeper.tracelog.dir=${zookeeper.log.dir}
-# zookeeper.tracelog.file=zookeeper_trace.log
-
-log4j.rootLogger=${zookeeper.root.logger}
-
-#
-# console
-# Add "console" to rootlogger above if you want to use this 
-#
-log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
-log4j.appender.CONSOLE.Threshold=${zookeeper.console.threshold}
-log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
-log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} [myid:%X{myid}] - %-5p [%t:%C{1}@%L] - %m%n
-
-# #
-# # Add ROLLINGFILE to rootLogger to get log file output
-# #
-# log4j.appender.ROLLINGFILE=org.apache.log4j.RollingFileAppender
-# log4j.appender.ROLLINGFILE.Threshold=${zookeeper.log.threshold}
-# log4j.appender.ROLLINGFILE.File=${zookeeper.log.dir}/${zookeeper.log.file}
-# log4j.appender.ROLLINGFILE.MaxFileSize=${zookeeper.log.maxfilesize}
-# log4j.appender.ROLLINGFILE.MaxBackupIndex=${zookeeper.log.maxbackupindex}
-# log4j.appender.ROLLINGFILE.layout=org.apache.log4j.PatternLayout
-# log4j.appender.ROLLINGFILE.layout.ConversionPattern=%d{ISO8601} [myid:%X{myid}] - %-5p [%t:%C{1}@%L] - %m%n
-
-# #
-# # Add TRACEFILE to rootLogger to get log file output
-# #    Log TRACE level and above messages to a log file
-# #
-# log4j.appender.TRACEFILE=org.apache.log4j.FileAppender
-# log4j.appender.TRACEFILE.Threshold=TRACE
-# log4j.appender.TRACEFILE.File=${zookeeper.tracelog.dir}/${zookeeper.tracelog.file}
-
-# log4j.appender.TRACEFILE.layout=org.apache.log4j.PatternLayout
-# ### Notice we are including log4j's NDC here (%x)
-# log4j.appender.TRACEFILE.layout.ConversionPattern=%d{ISO8601} [myid:%X{myid}] - %-5p [%t:%C{1}@%L][%x] - %m%n
-# #
-# # zk audit logging
-# #
-# zookeeper.auditlog.file=zookeeper_audit.log
-# zookeeper.auditlog.threshold=INFO
-# audit.logger=INFO, CONSOLE
-# log4j.logger.org.apache.zookeeper.audit.Log4jAuditLogger=${audit.logger}
-# log4j.additivity.org.apache.zookeeper.audit.Log4jAuditLogger=false
-# log4j.appender.RFAAUDIT=org.apache.log4j.RollingFileAppender
-# log4j.appender.RFAAUDIT.File=${zookeeper.log.dir}/${zookeeper.auditlog.file}
-# log4j.appender.RFAAUDIT.layout=org.apache.log4j.PatternLayout
-# log4j.appender.RFAAUDIT.layout.ConversionPattern=%d{ISO8601} %p %c{2}: %m%n
-# log4j.appender.RFAAUDIT.Threshold=${zookeeper.auditlog.threshold}
-
-# # Max log file size of 10MB
-# log4j.appender.RFAAUDIT.MaxFileSize=10MB
-# log4j.appender.RFAAUDIT.MaxBackupIndex=10
--- a/tests/nixos-virtualization-arion-test/zookeeper/zoo.cfg
+++ b/tests/nixos-virtualization-arion-test/zookeeper/zoo.cfg
@ -1,3 +0,0 @@
-tickTime=2000
-dataDir=/data
-clientPort=2181
				`@ -1 +0,0 @@`
				`../../../../../examples/full-nixos/arion-compose.nix`
				`@ -1 +0,0 @@`
				`../../../../../examples/minimal/arion-compose.nix`
				`@ -1 +0,0 @@`
				`../../../../../examples/nixos-unit/arion-compose.nix`