diff --git a/.github/actions/generate-format/action.yml b/.github/actions/generate-format/action.yml
new file mode 100644
index 00000000..46f4b43c
--- /dev/null
+++ b/.github/actions/generate-format/action.yml
@@ -0,0 +1,37 @@
+name: Generate Format
+description: Build a NixOS configuration using the specified nixos-generators format
+inputs:
+  nix-exec-path:
+    description: Path to the nix executable
+    default: nix
+  format:
+    description: nixos-generate format name
+  system:
+    description: Target nixpkgs system (e.g. x86_64-linux)
+    default: x86_64-linux
+  nixpkgs-name:
+    description: Flake input name for the target nixpkgs version
+    default: nixpkgs
+  nixpkgs:
+    description: Search path/URL for the target nixpkgs
+    default: 'https://github.com/nixos/nixpkgs/archive/nixpkgs-unstable.tar.gz'
+  force-build:
+    description: Build the target format even if no corresponding flake check exists
+  flake:
+    description: Nix flake URL
+    default: ${{ github.workspace }}
+runs:
+  using: composite
+  steps:
+  - name: Build the "${{ inputs.format }}" format
+    id: generate
+    shell: bash
+    run: ${{ github.action_path }}/generate-format.sh
+    env:
+      NIX_EXEC_PATH: ${{ inputs.nix-exec-path }}
+      FORMAT: ${{ inputs.format }}
+      SYSTEM: ${{ inputs.system }}
+      NIXPKGS_NAME: ${{ inputs.nixpkgs-name }}
+      NIXPKGS: ${{ inputs.nixpkgs }}
+      FORCE_BUILD: ${{ inputs.force-build }}
+      FLAKE: ${{ inputs.flake }}
diff --git a/.github/actions/generate-format/generate-format.sh b/.github/actions/generate-format/generate-format.sh
new file mode 100755
index 00000000..62a1268e
--- /dev/null
+++ b/.github/actions/generate-format/generate-format.sh
@@ -0,0 +1,74 @@
+#!/bin/sh
+
+set -x
+
+printenv
+
+die() {
+  rc="$?"
+  echo "::error file=nixos-generate::$*"
+  exit "$rc"
+}
+
+generate() {
+  timeout 20m \
+    "${NIX_EXEC_PATH:-nix}" run . \
+    -- \
+    -I "nixpkgs=${NIXPKGS?}" \
+    "$@"
+}
+
+getCheck() {
+  "${NIX_EXEC_PATH:-nix}" eval --json "${FLAKE:-.}#checks.\"${1?}\"" --apply "(builtins.hasAttr \"${2?}\")"
+}
+
+hasCheck() {
+  has_check=$(getCheck "$@") || die "failed to confirm availablity of check output"
+  [ "$has_check" = true ]
+}
+
+buildCheck() {
+  "${NIX_EXEC_PATH:-nix}" build "${FLAKE:-.}#checks.\"${1?}\".\"${2?}\""
+}
+
+buildAnyway() {
+  [ -n "${FORCE_BUILD:-}" ]
+}
+
+checkOutputs() {
+  path_var="$1"
+  shift
+
+  path="$1"
+  shift
+
+  test_type="$1"
+  shift
+
+  test "$test_type" "$path" || die "path $path does not exist or is not the expected type"
+  real=$(readlink -f "$path") || die "unable to resolve path to $path"
+  store_paths=$(nix-store -q --outputs "$real") || die "unable to get store path of $real"
+  echo "::set-output name=${path_var}::$(echo "$store_paths" | head -n 1)"
+}
+
+format="${FORMAT?}"
+system="${SYSTEM:-x86_64-linux}"
+nixpkgs_name="${NIXPKGS_NAME:-nixpkgs}"
+check="${format}-${nixpkgs_name}"
+out_link="./result-${format}"
+
+if hasCheck "$system" "$check"; then
+  : # NOP
+elif buildAnyway; then
+  buildCheck() { : ; }
+else
+  printf 1>&2 -- "No flake check defined for format '%s' on system '%s' using nixpkgs '%s', and force-building is not enabled; exiting.\\n" \
+    "$format" "$system" "$nixpkgs_name"
+
+  exit 0
+fi
+
+out=$(generate -f "$format" --system "$system" -o "$out_link") || die "build exited with status $?"
+buildCheck "$system" "$check" || die "flake build exited with status $?"
+checkOutputs out "$out" -f
+checkOutputs out_link "$out_link" -e
diff --git a/.github/actions/get-flake-input-rev/action.yml b/.github/actions/get-flake-input-rev/action.yml
new file mode 100644
index 00000000..0553c92a
--- /dev/null
+++ b/.github/actions/get-flake-input-rev/action.yml
@@ -0,0 +1,27 @@
+name: Get Rev
+description: Get a Nix flake input revision from the flake lock file
+inputs:
+  nix-exec-path:
+    description: Path to the nix executable
+    default: nix
+  flake-input-name:
+    description: Name of the flake input whose revision should be retrieved
+    default: nixpkgs
+  flake:
+    description: Nix flake URL
+    default: ${{ github.workspace }}
+outputs:
+  rev:
+    description: Locked revision of the flake input
+    value: ${{ steps.get-rev.outputs.rev }}
+runs:
+  using: composite
+  steps:
+  - name: Get flake input revision for "${{ inputs.flake-input-name }}" from ${{ inputs.flake-lock-path }}
+    id: get-rev
+    shell: bash
+    env:
+      NIX_EXEC_PATH: ${{ inputs.nix-exec-path }}
+      FLAKE_INPUT_NAME: ${{ inputs.flake-input-name }}
+      FLAKE: ${{ inputs.flake }}
+    run: ${{ github.action_path }}/get-flake-input-rev.sh
diff --git a/.github/actions/get-flake-input-rev/get-flake-input-rev.sh b/.github/actions/get-flake-input-rev/get-flake-input-rev.sh
new file mode 100755
index 00000000..89d02d66
--- /dev/null
+++ b/.github/actions/get-flake-input-rev/get-flake-input-rev.sh
@@ -0,0 +1,18 @@
+#!/bin/sh
+
+getRev() {
+  # Run in nix shell in order to use jq
+  # shellcheck disable=SC2016
+  "${NIX_EXEC_PATH:-nix}" develop "${FLAKE:-.}" --command \
+    bash -c '"$1" flake metadata --json "$2" | jq -r --arg input "$3" ".locks.nodes[\$input].locked.rev"' \
+      "$0" "${NIX_EXEC_PATH:-nix}" "${FLAKE:-.}" "${1?}"
+}
+
+rev=$(getRev "${FLAKE_INPUT_NAME:-nixpkgs}") || exit
+
+if [ "$rev" = null ]; then
+  echo "::error file=${FLAKE:-.}::unable to retrieve revision for flake input ${FLAKE_INPUT_NAME:-nixpkgs}"
+  exit 1
+fi
+
+echo "::set-output name=rev::${rev}"
diff --git a/.github/actions/list-formats/action.yml b/.github/actions/list-formats/action.yml
new file mode 100644
index 00000000..66049829
--- /dev/null
+++ b/.github/actions/list-formats/action.yml
@@ -0,0 +1,27 @@
+name: List Formats
+description: List available nixos-generators formats
+inputs:
+  nixos-generate-exec-path:
+    description: Path to the nixos-generate executable
+    default: ${{ github.workspace }}/nixos-generate
+  nix-exec-path:
+    description: Path to the nix executable
+    default: nix
+  flake:
+    description: Nix flake URL
+    default: ${{ github.workspace }}
+outputs:
+  formats:
+    description: Available nixos-generators formats
+    value: ${{ steps.list-formats.outputs.formats }}
+runs:
+  using: composite
+  steps:
+  - name: List available nixos-generators formats
+    id: list-formats
+    shell: bash
+    env:
+      NIXOS_GENERATE_EXEC_PATH: ${{ inputs.nixos-generate-exec-path }}
+      NIX_EXEC_PATH: ${{ inputs.nix-exec-path }}
+      FLAKE: ${{ inputs.flake }}
+    run: ${{ github.action_path }}/list-formats.sh
diff --git a/.github/actions/list-formats/list-formats.sh b/.github/actions/list-formats/list-formats.sh
new file mode 100755
index 00000000..c125c04e
--- /dev/null
+++ b/.github/actions/list-formats/list-formats.sh
@@ -0,0 +1,12 @@
+#!/bin/sh
+
+listFormats() {
+  # Run in nix shell in order to use jq
+  # shellcheck disable=SC2016
+  "${NIX_EXEC_PATH:-nix}" develop "${FLAKE:-.}" --command \
+    bash -c '"$1" --list | jq -cnMR "[inputs]"' \
+      "$0" "${NIXOS_GENERATE_EXEC_PATH:-./nixos-generate}"
+}
+
+formats=$(listFormats) || exit
+echo "::set-output name=formats::${formats}"
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index ca373b9e..e9d1ad4c 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -11,10 +11,127 @@ jobs:
     steps:
     - uses: actions/checkout@v3
       with:
-          # Nix Flakes doesn't work on shallow clones
-          fetch-depth: 0
+        # Nix Flakes doesn't work on shallow clones
+        fetch-depth: 0
     - uses: cachix/install-nix-action@v17
     - name: List flake structure
       run: nix flake show
     - name: Run unit tests (flake)
       run: nix build -L
+  check:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        fetch-depth: 0
+    - uses: cachix/install-nix-action@v17
+    - name: Run flake checks
+      run: nix flake check --no-build --keep-going
+  introspect:
+    runs-on: ubuntu-latest
+    outputs:
+      nixpkgs-rev: ${{ steps.nixpkgs-rev.outputs.rev }}
+      nixos-rev: ${{ steps.nixos-rev.outputs.rev }}
+      formats: ${{ steps.list-formats.outputs.formats }}
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        fetch-depth: 0
+    - uses: cachix/install-nix-action@v17
+    - name: Get nixpkgs flake input rev
+      id: nixpkgs-rev
+      uses: ./.github/actions/get-flake-input-rev
+      with:
+        flake-input-name: nixpkgs
+    - name: Get nixos flake input rev
+      id: nixos-rev
+      uses: ./.github/actions/get-flake-input-rev
+      with:
+        flake-input-name: nixos
+    - name: List available formats
+      id: list-formats
+      if: github.event_name == 'push' && github.ref == 'refs/heads/master'
+      uses: ./.github/actions/list-formats
+  default-formats:
+    strategy:
+      matrix:
+        format:
+        - amazon
+        - docker
+        - iso
+        - kexec-bundle
+        nixpkgs-name:
+        - nixpkgs
+        - nixos
+        include:
+        - nixpkgs-name: nixpkgs
+          nixpkgs: 'https://github.com/nixos/nixpkgs/archive/${{ needs.introspect.outputs.nixpkgs-rev }}.tar.gz'
+        - nixpkgs-name: nixos
+          nixpkgs: 'https://github.com/nixos/nixpkgs/archive/${{ needs.introspect.outputs.nixos-rev }}.tar.gz'
+        - format: kexec-bundle
+          force-build: yes
+    runs-on: ubuntu-latest
+    needs: [ 'check', 'introspect' ]
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        fetch-depth: 0
+    - uses: cachix/install-nix-action@v17
+      with:
+        # kvm required for a number of formats; big-parallel required for
+        # proxmox and possibly others.
+        extra_nix_config: |
+          system-features = big-parallel kvm
+    - name: Build the "${{ matrix.format }}" format
+      id: generate
+      uses: ./.github/actions/generate-format
+      with:
+        format: ${{ matrix.format }}
+        system: ${{ matrix.system }}
+        nixpkgs-name: ${{ matrix.nixpkgs-name }}
+        nixpkgs: ${{ matrix.nixpkgs }}
+        force-build: ${{ matrix.force-build }}
+  all-formats:
+    if: github.event_name == 'push' && github.ref == 'refs/heads/master'
+    strategy:
+      matrix:
+        format: ${{ needs.introspect.outputs.formats && fromJSON(needs.introspect.outputs.formats) }}
+        nixpkgs-name:
+        - nixpkgs
+        - nixos
+        include:
+        - nixpkgs-name: nixpkgs
+          nixpkgs: 'https://github.com/nixos/nixpkgs/archive/${{ needs.introspect.outputs.nixpkgs-rev }}.tar.gz'
+        - nixpkgs-name: nixos
+          nixpkgs: 'https://github.com/nixos/nixpkgs/archive/${{ needs.introspect.outputs.nixos-rev }}.tar.gz'
+        - format: kexec-bundle
+          force-build: yes
+        - format: sd-aarch64-installer
+          system: aarch64-linux
+        - format: sd-aarch64
+          system: aarch64-linux
+    runs-on: ubuntu-latest
+    needs: [ 'check', 'introspect' ]
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        fetch-depth: 0
+    # set up qemu if we are targeting a non-native system
+    - uses: docker/setup-qemu-action@v2
+      if: ${{ matrix.system }}
+    - uses: cachix/install-nix-action@v17
+      with:
+        # kvm required for a number of formats; big-parallel required for
+        # proxmox and possibly others.
+        extra_nix_config: |
+          system-features = big-parallel kvm
+          extra-platforms = ${{ matrix.system }}
+    - name: Build the "${{ matrix.format }}" format
+      id: generate
+      uses: ./.github/actions/generate-format
+      with:
+        format: ${{ matrix.format }}
+        system: ${{ matrix.system }}
+        nixpkgs-name: ${{ matrix.nixpkgs-name }}
+        nixpkgs: ${{ matrix.nixpkgs }}
+        force-build: ${{ matrix.force-build }}
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
deleted file mode 100644
index 54162653..00000000
--- a/.gitlab-ci.yml
+++ /dev/null
@@ -1,132 +0,0 @@
-include: .included.yml
-
-variables:
-    GIT_DEPTH: 1
-    nixpkgs_ver: "19.09"
-    uploadPath: ./nixos-$CI_JOB_NAME-$CI_PIPELINE_ID
-
-# job names are sorted alphabetically
-
-azure:
-    variables:
-        formats: azure
-    extends:
-        - .template
-
-# doesn't build
-.cloudstack:
-    variables:
-        formats: cloudstack
-    extends:
-        - .template
-
-do:
-    variables:
-        nixpkgs_ver: unstable
-        formats: do
-    extends:
-        - .template
-
-gce:
-    variables:
-        formats: gce
-    extends:
-        - .template
-
-install-iso:
-    variables:
-        formats: install-iso
-    extends:
-        - .template
-
-install-iso-hyperv:
-    variables:
-        formats: install-iso-hyperv
-    extends:
-        - .template
-
-iso:
-    variables:
-        formats: iso
-    extends:
-        - .template
-
-kexec:
-    variables:
-        formats: kexec
-    extends:
-        - .template
-
-kexec-bundle:
-    variables:
-        formats: kexec-bundle
-    extends:
-        - .template
-
-lxc:
-    variables:
-        formats: lxc
-    extends:
-        - .template
-
-lxc-metadata:
-    variables:
-        formats: lxc-metadata
-    extends:
-        - .template
-
-openstack:
-    variables:
-        formats: openstack
-    extends:
-        - .template
-
-qcow:
-    variables:
-        formats: qcow
-    extends:
-        - .template
-
-raw:
-    variables:
-        formats: raw
-    extends:
-        - .template
-
-# todo
-.sd-aarch64:
-    variables:
-        formats: sd-aarch64
-    script:
-        - nix-shell --command './nixos-generate -f $formats --nixpkgs_ver $nixpkgs_ver --system aarch64-linux'
-    extends:
-        - .template
-
-# todo
-.sd-aarch64-installer:
-    variables:
-        formats: sd-aarch64-installer
-    script:
-        - nix-shell --command './nixos-generate -f $formats --nixpkgs_ver $nixpkgs_ver --system aarch64-linux'
-    extends:
-        - .template
-
-virtualbox:
-    variables:
-        formats: virtualbox
-    extends:
-        - .template
-
-vm:
-    variables:
-        formats: vm
-    extends:
-        - .template
-        - .tar_option
-
-vm-nogui:
-    variables:
-        formats: vm-nogui
-    extends:
-        - .template
-        - .tar_option
diff --git a/.included.yml b/.included.yml
deleted file mode 100644
index 46055608..00000000
--- a/.included.yml
+++ /dev/null
@@ -1,29 +0,0 @@
-stages:
-    - build
-
-.tar_option:
-    after_script:
-        - tar -cvhf $uploadPath.tar ./$uploadPath
-    artifacts:
-        name: "$uploadPath"
-        paths:
-        - $uploadPath.tar
-
-.template:
-    only:
-        - web
-    stage: build
-    image: lnl7/nix:latest
-    before_script:
-        - nix --version
-        - chmod +w /etc/nix/nix.conf
-        - echo "system-features = kvm" >> /etc/nix/nix.conf
-        - sed -i -e 's/ --no-out-link//g' nixos-generate
-        - mkdir $uploadPath
-    script:
-        - nix-shell --command './nixos-generate -f $formats -I nixpkgs=channel:nixos-$nixpkgs_ver' |& tee $uploadPath/build.log
-        - mv $(realpath result) $uploadPath
-    artifacts:
-        name: "$uploadPath"
-        paths:
-        - $uploadPath
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 4da991be..00000000
--- a/.travis.yml
+++ /dev/null
@@ -1,6 +0,0 @@
-language: nix
-
-sudo: false
-
-script:
-  - nix-build
diff --git a/Makefile b/Makefile
index 439bfe04..50acd4e2 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@ SHARE ?= $(PREFIX)/share/nixos-generator
 
 all:
 
-SOURCES = formats format-module.nix configuration.nix nixos-generate.nix
+SOURCES = formats format-module.nix configuration.nix lib.nix nixos-generate.nix
 
 install:
 	mkdir -p $(PREFIX)/bin $(SHARE)
diff --git a/README.md b/README.md
index 018af195..0178c326 100644
--- a/README.md
+++ b/README.md
@@ -98,13 +98,52 @@ NIX_PATH=nixpkgs=../nixpkgs nixos-generate -f do
 
 ## Cross Compiling
 
-To cross compile nixos images for other system you have
-to configure `boot.binfmtMiscRegistrations` on your host system.
+To cross compile nixos images for other architectures you have to configure
+`boot.binfmt.emulatedSystems` or `boot.binfmt.registrations` on your host system.
 
-For more details about this have a look at :
+In your system `configuration.nix`:
+```nix
+{
+  # Enable binfmt emulation of aarch64-linux.
+  boot.binfmt.emulatedSystems = [ "aarch64-linux" ];
+}
+```
+
+Alternatively, if you want to target other architectures:
+```nix
+# Define qemu-arm-static source.
+let qemu-arm-static = pkgs.stdenv.mkDerivation {
+  name = "qemu-arm-static";
+  src = builtins.fetchurl {
+    url = "https://github.com/multiarch/qemu-user-static/releases/download/v6.1.0-8/qemu-arm-static";
+    sha256 = "06344d77d4f08b3e1b26ff440cb115179c63ca8047afb978602d7922a51231e3";
+  };
+  dontUnpack = true;
+  installPhase = "install -D -m 0755 $src $out/bin/qemu-arm-static";
+};
+in {
+  # Enable binfmt emulation of extra binary formats (armv7l-linux, for exmaple).
+  boot.binfmt.registrations.arm = {
+    interpreter = "${qemu-arm-static}/bin/qemu-arm-static";
+    magicOrExtension = ''\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00'';
+    mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\x00\xff\xfe\xff\xff\xff'';
+  };
+
+  # Define additional settings for nix.
+  nix.extraOptions = ''
+    extra-platforms = armv7l-linux
+  '';
+  nix.sandboxPaths = [ "/run/binfmt/arm=${qemu-arm-static}/bin/qemu-arm-static" ];
+}
+```
+
+For more details on configuring `binfmt`, have a look at:
+[binfmt options](https://search.nixos.org/options?channel=unstable&query=boot.binfmt),
+[binfmt.nix](https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/system/boot/binfmt.nix),
+[this comment](https://github.com/NixOS/nixpkgs/issues/109661#issuecomment-762629438) and
 [clevers qemu-user](https://github.com/cleverca22/nixos-configs/blob/master/qemu.nix).
 
-Once you've run `nixos-rebuild` with theses options,
+Once you've run `nixos-rebuild` with these options,
 you can use the `--system` option to create images for other architectures.
 
 ## Using in a Flake
diff --git a/flake.lock b/flake.lock
index 8cdc03b5..1aef49a2 100644
--- a/flake.lock
+++ b/flake.lock
@@ -15,13 +15,29 @@
         "type": "github"
       }
     },
+    "nixos": {
+      "locked": {
+        "lastModified": 1652881001,
+        "narHash": "sha256-k9JmPCojaJnqGz4aRXXT1HZqJKHCXijoMfBAb24abXk=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "2d474d6a4a43a0348b78db68dc00c491032cf5cf",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-21.11",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1637186689,
-        "narHash": "sha256-NU7BhgnwA/3ibmCeSzFK6xGi+Bari9mPfn+4cBmyEjw=",
+        "lastModified": 1652739558,
+        "narHash": "sha256-znGkjGugajqF/sFS+H4+ENmGTaVPFE0uu1JjQZJLEaQ=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "7fad01d9d5a3f82081c00fb57918d64145dc904c",
+        "rev": "ff691ed9ba21528c1b4e034f36a04027e4522c58",
         "type": "github"
       },
       "original": {
@@ -34,6 +50,7 @@
     "root": {
       "inputs": {
         "nixlib": "nixlib",
+        "nixos": "nixos",
         "nixpkgs": "nixpkgs"
       }
     }
diff --git a/flake.nix b/flake.nix
index 6fb163d6..9cac5314 100644
--- a/flake.nix
+++ b/flake.nix
@@ -6,8 +6,9 @@
 
   # Bin dependency
   inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  inputs.nixos.url = "github:NixOS/nixpkgs/nixos-21.11";
 
-  outputs = { self, nixpkgs, nixlib }:
+  outputs = { self, nixpkgs, nixos, nixlib }@inputs:
 
   # Library modules (depend on nixlib)
   rec {
@@ -18,16 +19,15 @@
       value.imports = [ (./formats + "/${file}") ./format-module.nix ];
     }) (builtins.readDir ./formats);
 
-    # example usage in flakes:
-    #   outputs = { self, nixpkgs, nixos-generators, ...}: {
-    #     vmware = nixos-generators.nixosGenerate {
-    #       pkgs = nixpkgs.legacyPackages.x86_64-linux;
-    #       modules = [./configuration.nix];
-    #       format = "vmware";
-    #   };
-    # }
-    nixosGenerate = { pkgs, format,  specialArgs ? { }, modules ? [ ] }:
-    let 
+    nixosGenerate' = {
+      format
+    , system
+    , nixpkgs ? inputs.nixpkgs
+    , pkgs ? nixpkgs.legacyPackages.${system}
+    , specialArgs ? { }
+    , modules ? [ ]
+    }:
+    let
       formatModule = builtins.getAttr format nixosModules;
       image = nixpkgs.lib.nixosSystem {
         inherit pkgs specialArgs;
@@ -36,14 +36,26 @@
           formatModule
         ] ++ modules;
       };
-    in
+    in assert system == pkgs.system;
       image.config.system.build.${image.config.formatAttr};
 
+    # example usage in flakes:
+    #   outputs = { self, nixpkgs, nixos-generators, ...}: {
+    #     vmware = nixos-generators.nixosGenerate {
+    #       pkgs = nixpkgs.legacyPackages.x86_64-linux;
+    #       modules = [./configuration.nix];
+    #       format = "vmware";
+    #   };
+    # }
+    nixosGenerate = { pkgs, format, specialArgs ? { }, modules ? [ ] }:
+      nixosGenerate' {
+        system = pkgs.system;
+        inherit pkgs format specialArgs modules;
+      };
   }
 
   //
 
-
   # Binary and Devshell outputs (depend on nixpkgs)
   (
     let
@@ -74,15 +86,117 @@
         buildInputs = with pkgs; [ jq coreutils findutils ];
       });
 
-      # Make it runnable with `nix app`
-      apps = forAllSystems (system: {
+      # Make it runnable with `nix run`
+      apps = forAllSystems (system: let
         nixos-generate = {
           type    = "app";
           program = "${self.packages."${system}".nixos-generators}/bin/nixos-generate";
         };
+      in {
+        inherit nixos-generate;
+
+        # Nix >= 2.7 flake output schema uses `apps.<system>.default` instead
+        # of `defaultApp.<system>` to signify the default app (the thing that
+        # gets run with `nix run . -- <args>`)
+        default = nixos-generate;
       });
 
       defaultApp = forAllSystems (system: self.apps."${system}".nixos-generate);
+
+      checks = let
+        # No way to limit `nix flake check` to a subset of supported systems;
+        # see https://github.com/NixOS/nix/issues/6398.
+        forCheckSystems = nixpkgs.lib.genAttrs [ "x86_64-linux" "aarch64-linux" ];
+
+        checksForNixpkgs =
+          system:
+          {
+            input,
+            id,
+            modules ? (fetchModules system id)
+          }:
+        let
+          pkgs = input.legacyPackages.${system};
+          generateFormat = format: self.nixosGenerate' {
+            inherit format system pkgs;
+            nixpkgs = input;
+          };
+          #formatModules = builtins.removeAttrs self.nixosModules exclude;
+        in nixlib.lib.mapAttrs' (format: _: let
+          name = "${format}-${id}";
+          diag = ''evaluating format "${format}" using nixpkgs input "${id}" on system "${system}"'';
+          value = nixlib.lib.trace diag (generateFormat format);
+        in {
+          inherit name value;
+        }) modules;
+
+        fetchModules = let
+          excludeCommon = [
+            # error:
+            #      Failed assertions:
+            #      - Mountpoint '/': 'autoResize = true' is not supported for 'fsType = "auto"': fsType has to be explicitly set and only the ext filesystems and f2fs support it.
+            "cloudstack"
+
+            # error (ignored): error: cannot look up '<nixpkgs/nixos/lib/make-system-tarball.nix>' in pure evaluation mode (use '--impure' to override)
+            #
+            #       at /nix/store/0b099b46lb9dmhwzyc2zgjk8lp8d9rfq-source/kexec/kexec.nix:42:49:
+            #
+            #           41|   '';
+            #           42|   system.build.kexec_tarball = pkgs.callPackage <nixpkgs/nixos/lib/make-system-tarball.nix> {
+            #             |                                                 ^
+            #           43|     storeContents = [
+            "kexec"
+            "kexec-bundle"
+          ];
+
+          excludeNixpkgs = [
+            # error: path '/nix/store/0bsydzh62cn1by07j5cjy28crbnbc5wz-google-guest-configs-20211116.00.drv' is not valid)
+            "gce"
+
+            # Compilation error in some prerequisite or other.
+            "proxmox"
+          ];
+
+          excludeNixos = [
+            # error: getting status of '/nix/store/<...>/nixos/modules/virtualisation/kubevirt.nix': No such file or directory
+            "kubevirt"
+
+            # error: getting status of '/nix/store/<...>/nixos/modules/virtualisation/proxmox-lxc.nix': No such file or directory
+            "proxmox-lxc"
+          ];
+
+          aarch64Only = [ "sd-aarch64" "sd-aarch64-installer" ];
+
+          baseModules = builtins.removeAttrs self.nixosModules excludeCommon;
+          nixpkgsModules = builtins.removeAttrs baseModules excludeNixpkgs;
+          nixosModules = builtins.removeAttrs baseModules excludeNixos;
+
+          matrix = {
+            "x86_64-linux" = {
+              "nixpkgs" = builtins.removeAttrs nixpkgsModules aarch64Only;
+              "nixos" = builtins.removeAttrs nixosModules aarch64Only;
+            };
+
+            "aarch64-linux" = {
+              "nixpkgs" = nixlib.lib.getAttrs aarch64Only nixpkgsModules;
+              "nixos" = nixlib.lib.getAttrs aarch64Only nixosModules;
+            };
+          };
+        in system: id: matrix.${system}.${id};
+      in
+      forCheckSystems (system: let
+        checksForNixpkgs' = checksForNixpkgs system;
+
+        nixpkgsChecks = checksForNixpkgs' {
+          input = nixpkgs;
+          id = "nixpkgs";
+        };
+
+        nixosChecks = checksForNixpkgs' {
+          input = nixos;
+          id = "nixos";
+        };
+      in nixpkgsChecks // nixosChecks);
     }
   );
 }
diff --git a/formats/kexec-bundle.nix b/formats/kexec-bundle.nix
index e18bce0f..e2878d76 100644
--- a/formats/kexec-bundle.nix
+++ b/formats/kexec-bundle.nix
@@ -3,4 +3,5 @@
   imports = [ ./kexec.nix ];
 
   formatAttr = lib.mkForce "kexec_bundle";
+  filename = lib.mkForce "*-kexec_bundle";
 }
diff --git a/formats/kexec.nix b/formats/kexec.nix
index a124454d..47878fbb 100644
--- a/formats/kexec.nix
+++ b/formats/kexec.nix
@@ -1,9 +1,11 @@
-{ config, pkgs, lib, modulesPath, ... }: let
+{ config, pkgs, lib, modulesPath, options, ... }: let
 
   clever-tests = builtins.fetchGit {
     url = "https://github.com/cleverca22/nix-tests";
     rev = "a9a316ad89bfd791df4953c1a8b4e8ed77995a18"; # master on 2021-06-13
   };
+
+  inherit (import ../lib.nix { inherit lib options; }) maybe;
 in {
   imports = [
     "${toString modulesPath}/installer/netboot/netboot-minimal.nix"
@@ -13,7 +15,7 @@ in {
   ];
 
   system.build = rec {
-    kexec_tarball = lib.mkForce (pkgs.callPackage "${toString modulesPath}/../lib/make-system-tarball.nix" {
+    kexec_tarball = maybe.mkForce (pkgs.callPackage "${toString modulesPath}/../lib/make-system-tarball.nix" {
       storeContents = [
         { object = config.system.build.kexec_script; symlink = "/kexec_nixos"; }
       ];
diff --git a/formats/raw-efi.nix b/formats/raw-efi.nix
index f185a913..6ebabad7 100644
--- a/formats/raw-efi.nix
+++ b/formats/raw-efi.nix
@@ -1,5 +1,8 @@
-{ config, lib, pkgs, modulesPath, ... }:
-{
+{ config, lib, options, pkgs, modulesPath, ... }:
+
+let
+  inherit (import ../lib.nix { inherit lib options; }) maybe;
+in {
   imports = [ ./raw.nix ];
 
   boot.loader.grub = {
@@ -8,7 +11,12 @@
     efiInstallAsRemovable = true;
   };
 
-  system.build.raw = lib.mkOverride 999 (import "${toString modulesPath}/../lib/make-disk-image.nix" {
+  fileSystems."/boot" = {
+    device = "/dev/vda1";
+    fsType = "vfat";
+  };
+
+  system.build.raw = maybe.mkOverride 99 (import "${toString modulesPath}/../lib/make-disk-image.nix" {
     inherit lib config pkgs;
     partitionTableType = "efi";
     diskSize = "auto";
diff --git a/formats/vm-nogui.nix b/formats/vm-nogui.nix
index b5b627be..449baf91 100644
--- a/formats/vm-nogui.nix
+++ b/formats/vm-nogui.nix
@@ -8,7 +8,7 @@ let
       IFS=';t' read -r _ rows cols _ < /dev/tty
       stty "$old"
       stty cols "$cols" rows "$rows"
-    ]
+    fi
   ''; # https://unix.stackexchange.com/questions/16578/resizable-serial-console-window
 in {
   imports = [
diff --git a/lib.nix b/lib.nix
new file mode 100644
index 00000000..83e365e0
--- /dev/null
+++ b/lib.nix
@@ -0,0 +1,32 @@
+{
+  lib,
+  options,
+}: let
+  # See https://github.com/NixOS/nixpkgs/commit/ccb85a53b6a496984073227fd8c4d4c58889f421
+  # This commit changed the type of `system.build` from a lazy attribute set to
+  # a submodule.  Prior to this commit, it doesn't make sense to qualify, e.g.
+  # the `system.build.kexec_tarball` definition with `lib.mkForce`, as this
+  # would result in setting the (final/resolved) value of
+  # `system.build.kexec_tarball` to something like:
+  #   {
+  #     _type = "override";
+  #     content = <...>;
+  #     priority = 50;
+  #   }
+  # However, since this commit, `system.build.kexec_tarball` *must* be defined
+  # using `lib.mkForce`; otherwise, Nix bails out with a complaint about
+  # `system.build.kexec_tarball` being defined in multiple locations.
+  systemBuildIsSubmodule = options.system.build.type.name == "submodule";
+
+  optionsLookSane = lib.hasAttrByPath ["system" "build" "type" "name"] options;
+in
+  assert (lib.assertMsg optionsLookSane "`options' must be the NixOS module `options' argument"); {
+    maybe =
+      {
+        mkForce = lib.id;
+        mkOverride = _: lib.id;
+      }
+      // (lib.optionalAttrs systemBuildIsSubmodule {
+        inherit (lib) mkForce mkOverride;
+      });
+  }
diff --git a/nixos-generate b/nixos-generate
index 40a0151c..d3adbb24 100755
--- a/nixos-generate
+++ b/nixos-generate
@@ -41,7 +41,7 @@ Options:
 * --system: specify the target system (eg: x86_64-linux)
 * -o, --out-link: specify the outlink location for nix-build
 * --cores : to control the maximum amount of parallelism. (see nix-build documentation)
-* --option : Passed to to nix-build (see nix-build documentation).
+* --option : Passed to nix-build (see nix-build documentation).
 * -I KEY=VALUE: Add a key to the Nix expression search path.
 USAGE
 }
@@ -169,7 +169,7 @@ out=$(nix-build "${nix_args[@]}" "${nix_build_args[@]}" -A "config.system.build.
 
 if [[ -z $run ]]; then
   # show the first file, ignoring nix-support
-  find "$out" -wholename "$filename" -type f -print -quit
+  find "$out" -wholename "$filename" -xtype f -print -quit
 else
   runner=$(find "$out"/bin -type l -print -quit)
   exec "$runner"