From dcb0c42857a2ada8754d4514d4b8c4c1d67ab3f5 Mon Sep 17 00:00:00 2001
From: lassulus <lassulus@lassul.us>
Date: Mon, 29 Aug 2022 11:45:19 +0200
Subject: [PATCH] reimplement disko using the nixos type system

This should make the code cleaner, more robust and errors should be
clearer. we also changed the configuration format a bit.
---
 default.nix                  |  328 +----------
 example/btrfs-subvolumes.nix |   43 +-
 example/complex.nix          |  194 +++++++
 example/luks-lvm.nix         |  132 ++---
 example/lvm-raid.nix         |  114 ++--
 example/mdadm.nix            |   72 ++-
 example/zfs-over-legacy.nix  |   63 +-
 example/zfs.nix              |   53 +-
 tests/complex.nix            |   20 +
 tests/lib.nix                |    2 +-
 types.nix                    | 1058 ++++++++++++++++++++++++++++++++++
 11 files changed, 1545 insertions(+), 534 deletions(-)
 create mode 100644 example/complex.nix
 create mode 100644 tests/complex.nix
 create mode 100644 types.nix

diff --git a/default.nix b/default.nix
index 51b70f5..9febd80 100644
--- a/default.nix
+++ b/default.nix
@@ -1,312 +1,22 @@
-{ lib ? import <nixpkgs/lib> }:
-with lib;
-with builtins;
-
+{ lib ? import <nixpkgs/lib>
+, pkgs ? import <nixpkgs> {}
+}:
 let
-
-  helper.find-device = device:
-    let
-      environment = helper.device-id device;
-    in
-    # DEVICE points already to /dev/disk, so we don't handle it via /dev/disk/by-path
-    if hasPrefix "/dev/disk" device then
-      "${environment}='${device}'"
-    else ''
-      ${environment}=$(for x in $(find /dev/disk/{by-path,by-id}/); do
-        dev=$x
-        if [ "$(readlink -f $x)" = "$(readlink -f '${device}')" ]; then
-          target=$dev
-          break
-        fi
-      done
-      if test -z ''${target+x}; then
-        echo 'unable to find path of disk: ${device}, bailing out' >&2
-        exit 1
-      else
-        echo $target
-      fi)
-    '';
-
-  helper.device-id = device: "DEVICE${builtins.substring 0 5 (builtins.hashString "sha1" device)}";
-
-  config-f = q: x: config.${x.type} q x;
-
-  config.filesystem = q: x: {
-    fileSystems.${x.mountpoint} = {
-      device = q.device;
-      fsType = x.format;
-      ${if x ? options then "options" else null} = x.options;
-    };
-  };
-
-  config.zfs_filesystem = q: x: {
-    fileSystems.${x.mountpoint} = {
-      device = q.device;
-      fsType = "zfs";
-    };
-  };
-
-  config.devices = q: x:
-    foldl' recursiveUpdate { } (mapAttrsToList (name: config-f { device = "/dev/${name}"; }) x.content);
-
-  config.luks = q: x: {
-    boot.initrd.luks.devices.${x.name}.device = q.device;
-  } // config-f { device = "/dev/mapper/${x.name}"; } x.content;
-
-  config.lvm_lv = q: x:
-    config-f { device = "/dev/${q.vgname}/${q.name}"; } x.content;
-
-  config.lvm_vg = q: x:
-    foldl' recursiveUpdate { } (mapAttrsToList (name: config-f { inherit name; vgname = x.name; }) x.lvs);
-
-  config.noop = q: x: { };
-
-  config.partition = q: x:
-    config-f { device = q.device + toString q.index; } x.content;
-
-  config.table = q: x:
-    foldl' recursiveUpdate { } (imap (index: config-f (q // { inherit index; })) x.partitions);
-
-
-  create-f = q: x: create.${x.type} q x;
-
-  create.btrfs = q: x: ''
-    mkfs.btrfs ${q.device}
-    ${lib.optionalString (!isNull x.subvolumes or null) ''
-      MNTPOINT=$(mktemp -d)
-      (
-        mount ${q.device} "$MNTPOINT"
-        trap 'umount $MNTPOINT; rm -rf $MNTPOINT' EXIT
-        ${concatMapStringsSep "\n" (subvolume: "btrfs subvolume create \"$MNTPOINT\"/${subvolume}") x.subvolumes}
-      )
-    ''}
-  '';
-
-  create.filesystem = q: x: ''
-    mkfs.${x.format} \
-      ${lib.optionalString (!isNull x.extraArgs or null) x.extraArgs} \
-      ${q.device}
-  '';
-
-  create.devices = q: x:
-    let
-      raid-devices = lib.filterAttrs (_: dev: dev.type == "mdadm" || dev.type == "zpool" || dev.type == "lvm_vg") x.content;
-      other-devices = lib.filterAttrs (_: dev: dev.type != "mdadm" && dev.type != "zpool" && dev.type != "lvm_vg") x.content;
-    in
-    ''
-      ${concatStrings (mapAttrsToList (name: create-f { device = "/dev/${name}"; }) other-devices)}
-      ${concatStrings (mapAttrsToList (name: create-f { device = "/dev/${name}"; name = name; }) raid-devices)}
-    '';
-
-  create.mdraid = q: x: ''
-    RAIDDEVICES_N_${x.name}=$((''${RAIDDEVICES_N_${x.name}:-0}+1))
-    RAIDDEVICES_${x.name}="''${RAIDDEVICES_${x.name}:-}${q.device} "
-  '';
-
-  create.mdadm = q: x: ''
-    echo 'y' | mdadm --create /dev/md/${q.name} --level=${toString x.level or 1} --raid-devices=''${RAIDDEVICES_N_${q.name}} ''${RAIDDEVICES_${q.name}}
-    udevadm trigger --subsystem-match=block; udevadm settle
-    ${create-f { device = "/dev/md/${q.name}"; } x.content}
-  '';
-
-  create.luks = q: x: ''
-    cryptsetup -q luksFormat ${q.device} ${if builtins.hasAttr "keyfile" x then x.keyfile else ""} ${toString (x.extraArgs or [])}
-    cryptsetup luksOpen ${q.device} ${x.name} ${if builtins.hasAttr "keyfile" x then "--key-file " + x.keyfile else ""}
-    ${create-f { device = "/dev/mapper/${x.name}"; } x.content}
-  '';
-
-  create.lvm_pv = q: x: ''
-    pvcreate ${q.device}
-    LVMDEVICES_${x.vg}="''${LVMDEVICES_${x.vg}:-}${q.device} "
-  '';
-
-  create.lvm_lv = q: x: ''
-    lvcreate \
-      ${if hasInfix "%" x.size then "-l" else "-L"} ${x.size} \
-      -n ${q.name} \
-      ${lib.optionalString (!isNull x.lvm_type or null) "--type=${x.lvm_type}"} \
-      ${lib.optionalString (!isNull x.extraArgs or null) x.extraArgs} \
-      ${q.vgname}
-    ${create-f { device = "/dev/${q.vgname}/${q.name}"; } x.content}
-  '';
-
-  create.lvm_vg = q: x: ''
-    vgcreate ${q.name} $LVMDEVICES_${q.name}
-    ${concatStrings (mapAttrsToList (name: create-f { inherit name; vgname = q.name; }) x.lvs)}
-  '';
-
-  create.noop = q: x: "";
-
-  create.partition = q: x:
-    let
-      env = helper.device-id q.device;
-    in
-    ''
-      parted -s "''${${env}}" mkpart ${x.part-type} ${x.fs-type or ""} ${x.start} ${x.end}
-      # ensure /dev/disk/by-path/..-partN exists before continuing
-      udevadm trigger --subsystem-match=block; udevadm settle
-      ${optionalString (x.bootable or false) ''
-        parted -s "''${${env}}" set ${toString q.index} boot on
-      ''}
-      ${concatMapStringsSep "" (flag: ''
-        parted -s "''${${env}}" set ${toString q.index} ${flag} on
-      '') (x.flags or [])}
-      ${create-f { device = "\"\${${env}}\"-part" + toString q.index; } x.content}
-    '';
-
-  create.table = q: x: ''
-    ${helper.find-device q.device}
-    parted -s "''${${helper.device-id q.device}}" mklabel ${x.format}
-    ${concatStrings (imap (index: create-f (q // { inherit index; })) x.partitions)}
-  '';
-
-  create.zfs = q: x: ''
-    ZFSDEVICES_${x.pool}="''${ZFSDEVICES_${x.pool}:-}${q.device} "
-  '';
-
-  create.zfs_filesystem = q: x: ''
-    zfs create ${q.pool}/${x.name} \
-      ${lib.optionalString (isAttrs x.options or null) (concatStringsSep " " (mapAttrsToList (n: v: "-o ${n}=${v}") x.options))}
-  '';
-
-  create.zfs_volume = q: x: ''
-    zfs create ${q.pool}/${x.name} \
-      -V ${x.size} \
-      ${lib.optionalString (isAttrs x.options or null) (concatStringsSep " " (mapAttrsToList (n: v: "-o ${n}=${v}") x.options))}
-    udevadm trigger --subsystem-match=block; udevadm settle
-    ${create-f { device = "/dev/zvol/${q.pool}/${x.name}"; } x.content}
-  '';
-
-  create.zpool = q: x: ''
-    zpool create ${q.name} \
-      ${lib.optionalString (!isNull (x.mode or null) && x.mode != "stripe") x.mode} \
-      ${lib.optionalString (isAttrs x.options or null) (concatStringsSep " " (mapAttrsToList (n: v: "-o ${n}=${v}") x.options))} \
-      ${lib.optionalString (isAttrs x.rootFsOptions or null) (concatStringsSep " " (mapAttrsToList (n: v: "-O ${n}=${v}") x.rootFsOptions))} \
-      ''${ZFSDEVICES_${q.name}}
-    ${concatMapStrings (create-f (q // { pool = q.name; })) x.datasets}
-  '';
-
-
-  mount-f = q: x: mount.${x.type} q x;
-
-  mount.filesystem = q: x: {
-    fs.${x.mountpoint} = ''
-      if ! findmnt ${q.device} "/mnt${x.mountpoint}" > /dev/null 2>&1; then
-        mount ${q.device} "/mnt${x.mountpoint}" \
-        -o X-mount.mkdir \
-        ${lib.optionalString (isList x.mountOptions or null) (concatStringsSep " " x.mountOptions)}
-      fi
-    '';
-  };
-
-  mount.zfs_filesystem = q: x:
-    optionalAttrs ((x.options.mountpoint or "") != "none")
-      (mount.filesystem (q // { device = q.dataset; }) (x // { mountOptions = [
-        (lib.optionalString ((x.options.mountpoint or "") != "legacy") "-o zfsutil")
-        "-t zfs"
-      ]; }));
-
-  mount.btrfs = mount.filesystem;
-
-  mount.devices = q: x:
-    let
-      z = foldl' recursiveUpdate { } (mapAttrsToList (name: mount-f { device = "/dev/${name}"; inherit name; }) x.content);
-      # attrValues returns values sorted by name.  This is important, because it
-      # ensures that "/" is processed before "/foo" etc.
-    in
-    ''
-      ${optionalString (hasAttr "table" z) (concatStringsSep "\n" (attrValues z.table))}
-      ${optionalString (hasAttr "luks" z) (concatStringsSep "\n" (attrValues z.luks))}
-      ${optionalString (hasAttr "lvm" z) (concatStringsSep "\n" (attrValues z.lvm))}
-      ${optionalString (hasAttr "zpool" z) (concatStringsSep "\n" (attrValues z.zpool))}
-      ${optionalString (hasAttr "zfs" z) (concatStringsSep "\n" (attrValues z.zfs))}
-      ${optionalString (hasAttr "fs" z) (concatStringsSep "\n" (attrValues z.fs))}
-    '';
-
-  mount.luks = q: x: (
-    recursiveUpdate
-      (mount-f { device = "/dev/mapper/${x.name}"; } x.content)
-      {
-        luks.${q.device} = ''
-          cryptsetup status ${x.name} >/dev/null 2>/dev/null || cryptsetup luksOpen ${q.device} ${x.name} ${if builtins.hasAttr "keyfile" x then "--key-file " + x.keyfile else ""}
-        '';
-      }
-  );
-
-  mount.lvm_lv = q: x:
-    mount-f { device = "/dev/${q.vgname}/${q.name}"; } x.content;
-
-  mount.lvm_vg = q: x: (
-    recursiveUpdate
-      (foldl' recursiveUpdate { } (mapAttrsToList (name: mount-f { inherit name; vgname = q.name; }) x.lvs))
-      {
-        lvm.${q.device} = ''
-          vgchange -a y
-        '';
-      }
-  );
-
-  mount.lvm_pv = mount.noop;
-
-  mount.noop = q: x: { };
-
-  mount.mdadm = q: x:
-    mount-f { device = "/dev/md/${q.name}"; } x.content;
-  mount.mdraid = mount.noop;
-
-  mount.partition = q: x:
-    mount-f { device = "\"\${${q.device}}\"-part" + toString q.index; } x.content;
-
-  mount.table = q: x: (
-    recursiveUpdate
-      (foldl' recursiveUpdate { } (imap (index: mount-f (q // { inherit index; device = helper.device-id q.device; })) x.partitions))
-      { table.${q.device} = helper.find-device q.device; }
-  );
-
-  mount.zfs = mount.noop;
-
-  mount.zpool = q: x:
-    let
-      datasets = [{
-        inherit (q) name;
-        type = "zfs_filesystem";
-        dataset = q.name;
-        mountpoint = x.mountpoint or "/${q.name}";
-        options = q.rootFsOptions or { };
-      }] ++ x.datasets;
-    in
-    recursiveUpdate
-      (foldl' recursiveUpdate { }
-        (
-          (map
-            (x: mount-f
-              ({
-                dataset = x.dataset or "${q.name}/${x.name}";
-                mountpoint = x.mountpoint or "/${q.name}/${x.name}";
-              } // q)
-              x)
-            datasets)
-        )
-      )
-      {
-        zpool.${q.device} = ''
-          zpool list '${q.name}' >/dev/null 2>/dev/null || zpool import '${q.name}'
-        '';
+  types = import ./types.nix { inherit pkgs; };
+  eval = cfg: lib.evalModules {
+    modules = lib.singleton {
+      # _file = toString input;
+      imports = lib.singleton { topLevel.devices = cfg; };
+      options = {
+        topLevel = lib.mkOption {
+          type = types.topLevel;
+        };
       };
-
-  mount.zfs_volume = q: x:
-    mount-f { device = "/dev/zvol/${q.dataset}"; } x.content;
-
-in
-{
-  config = config-f { };
-  create = cfg: ''
-    set -efux
-    ${create-f {} cfg}
-  '';
-  mount = cfg: ''
-    set -efux
-    ${mount-f {} cfg}
-  '';
-
+    };
+  };
+in {
+  types = types;
+  create = cfg: (eval cfg).config.topLevel.create;
+  mount = cfg: (eval cfg).config.topLevel.mount;
+  config = cfg: (eval cfg).config.topLevel.config;
 }
diff --git a/example/btrfs-subvolumes.nix b/example/btrfs-subvolumes.nix
index 0124c86..83ea71e 100644
--- a/example/btrfs-subvolumes.nix
+++ b/example/btrfs-subvolumes.nix
@@ -1,25 +1,28 @@
 {
-  type = "devices";
-  content = {
+  disk = {
     vdb = {
-      type = "table";
-      format = "gpt";
-      partitions = [
-        {
-          type = "partition";
-          part-type = "primary";
-          start = "0%";
-          end = "100%";
-          content = {
-            type = "btrfs";
-            mountpoint = "/";
-            subvolumes = [
-              "/home"
-              "/test"
-            ];
-          };
-        }
-      ];
+      type = "disk";
+      device = "/dev/vdb";
+      content = {
+        type = "table";
+        format = "gpt";
+        partitions = [
+          {
+            name = "root";
+            type = "partition";
+            start = "0%";
+            end = "100%";
+            content = {
+              type = "btrfs";
+              mountpoint = "/";
+              subvolumes = [
+                "/home"
+                "/test"
+              ];
+            };
+          }
+        ];
+      };
     };
   };
 }
diff --git a/example/complex.nix b/example/complex.nix
new file mode 100644
index 0000000..078f9c5
--- /dev/null
+++ b/example/complex.nix
@@ -0,0 +1,194 @@
+{
+  disk = {
+    disk1 = {
+      type = "disk";
+      device = "/dev/vdb";
+      content = {
+        type = "table";
+        format = "gpt";
+        partitions = [
+          {
+            type = "partition";
+            start = "0";
+            end = "1M";
+            name = "grub";
+            flags = ["bios_grub"];
+          }
+          {
+            type = "partition";
+            start = "1M";
+            end = "100%";
+            name = "luks";
+            bootable = true;
+            content = {
+              type = "luks";
+              name = "crypted1";
+              keyFile = "/tmp/secret.key";
+              extraArgs = [
+                "--hash sha512"
+                "--iter-time 5000"
+              ];
+              content = {
+                type = "lvm_pv";
+                vg = "pool";
+              };
+            };
+          }
+        ];
+      };
+    };
+    disk2 = {
+      type = "disk";
+      device = "/dev/vdc";
+      content = {
+        type = "table";
+        format = "gpt";
+        partitions = [
+          {
+            type = "partition";
+            start = "0";
+            end = "1M";
+            name = "grub";
+            flags = ["bios_grub"];
+          }
+          {
+            type = "partition";
+            start = "1M";
+            end = "100%";
+            name = "luks";
+            bootable = true;
+            content = {
+              type = "luks";
+              name = "crypted2";
+              keyFile = "/tmp/secret.key";
+              extraArgs = [
+                "--hash sha512"
+                "--iter-time 5000"
+              ];
+              content = {
+                type = "lvm_pv";
+                vg = "pool";
+              };
+            };
+          }
+        ];
+      };
+    };
+  };
+  mdadm = {
+    raid1 = {
+      type = "mdadm";
+      level = 1;
+      content = {
+        type = "table";
+        format = "msdos";
+        partitions = [
+          {
+            type = "partition";
+            name = "xfs";
+            start = "1MiB";
+            end = "100%";
+            content = {
+              type = "filesystem";
+              format = "xfs";
+              mountpoint = "/xfs_mdadm_lvm";
+            };
+          }
+        ];
+      };
+    };
+  };
+  lvm_vg = {
+    pool = {
+      type = "lvm_vg";
+      lvs = {
+        root = {
+          type = "lvm_lv";
+          size = "10M";
+          lvm_type = "mirror";
+          content = {
+            type = "filesystem";
+            format = "ext4";
+            mountpoint = "/ext4_on_lvm";
+            options = [
+              "defaults"
+            ];
+          };
+        };
+        raid1 = {
+          type = "lvm_lv";
+          size = "30M";
+          lvm_type = "raid0";
+          content = {
+            type = "mdraid";
+            name = "raid1";
+          };
+        };
+        raid2 = {
+          type = "lvm_lv";
+          size = "30M";
+          lvm_type = "raid0";
+          content = {
+            type = "mdraid";
+            name = "raid1";
+          };
+        };
+        zfs1 = {
+          type = "lvm_lv";
+          size = "128M";
+          lvm_type = "raid0";
+          content = {
+            type = "zfs";
+            pool = "zroot";
+          };
+        };
+        zfs2 = {
+          type = "lvm_lv";
+          size = "128M";
+          lvm_type = "raid0";
+          content = {
+            type = "zfs";
+            pool = "zroot";
+          };
+        };
+      };
+    };
+  };
+  zpool = {
+    zroot = {
+      type = "zpool";
+      mode = "mirror";
+      rootFsOptions = {
+        compression = "lz4";
+        "com.sun:auto-snapshot" = "false";
+      };
+      mountpoint = "/";
+
+      datasets = {
+        zfs_fs = {
+          zfs_type = "filesystem";
+          mountpoint = "/zfs_fs";
+          options."com.sun:auto-snapshot" = "true";
+        };
+        zfs_unmounted_fs = {
+          zfs_type = "filesystem";
+          options.mountpoint = "none";
+        };
+        zfs_legacy_fs = {
+          zfs_type = "filesystem";
+          options.mountpoint = "legacy";
+          mountpoint = "/zfs_legacy_fs";
+        };
+        zfs_testvolume = {
+          zfs_type = "volume";
+          size = "10M";
+          content = {
+            type = "filesystem";
+            format = "ext4";
+            mountpoint = "/ext4onzfs";
+          };
+        };
+      };
+    };
+  };
+}
diff --git a/example/luks-lvm.nix b/example/luks-lvm.nix
index 22c029e..17e18a2 100644
--- a/example/luks-lvm.nix
+++ b/example/luks-lvm.nix
@@ -1,81 +1,81 @@
 {
-  type = "devices";
-  content = {
+  disk = {
     vdb = {
-      type = "table";
-      format = "gpt";
-      partitions = [
-        {
-          type = "partition";
-          part-type = "ESP";
-          start = "1MiB";
-          end = "100MiB";
-          fs-type = "FAT32";
-          bootable = true;
-          content = {
-            type = "filesystem";
-            format = "vfat";
-            mountpoint = "/boot";
-            options = [
-              "defaults"
-            ];
-          };
-        }
-        {
-          type = "partition";
-          part-type = "primary";
-          start = "100MiB";
-          end = "100%";
-          content = {
-            type = "luks";
-            algo = "aes-xts...";
-            name = "crypted";
-            keyfile = "/tmp/secret.key";
-            extraArgs = [
-              "--hash sha512"
-              "--iter-time 5000"
-            ];
-            content = {
-              type = "lvm_pv";
-              vg = "pool";
-            };
-          };
-        }
-      ];
-    };
-    pool = {
-      type = "lvm_vg";
-        lvs = {
-          root = {
-            type = "lvm_lv";
-            size = "100M";
-            mountpoint = "/";
+      type = "disk";
+      device = "/dev/vdb";
+      content = {
+        type = "table";
+        format = "gpt";
+        partitions = [
+          {
+            type = "partition";
+            name = "ESP";
+            # fs-type = "FAT32";
+            start = "1MiB";
+            end = "100MiB";
+            bootable = true;
             content = {
               type = "filesystem";
-              format = "ext4";
-              mountpoint = "/";
+              format = "vfat";
+              mountpoint = "/boot";
               options = [
                 "defaults"
               ];
             };
-          };
-          home = {
-            type = "lvm_lv";
-            size = "10M";
+          }
+          {
+            type = "partition";
+            name = "luks";
+            start = "100MiB";
+            end = "100%";
             content = {
-              type = "filesystem";
-              format = "ext4";
-              mountpoint = "/home";
-            };
-          };
-          raw = {
-            type = "lvm_lv";
-            size = "10M";
-            content = {
-              type = "noop";
+              type = "luks";
+              name = "crypted";
+              keyFile = "/tmp/secret.key";
+              extraArgs = [
+                "--hash sha512"
+                "--iter-time 5000"
+              ];
+              content = {
+                type = "lvm_pv";
+                vg = "pool";
+              };
             };
+          }
+        ];
+      };
+    };
+  };
+  lvm_vg = {
+    pool = {
+      type = "lvm_vg";
+      lvs = {
+        root = {
+          type = "lvm_lv";
+          size = "100M";
+          content = {
+            type = "filesystem";
+            format = "ext4";
+            mountpoint = "/";
+            options = [
+              "defaults"
+            ];
           };
         };
+        home = {
+          type = "lvm_lv";
+          size = "10M";
+          content = {
+            type = "filesystem";
+            format = "ext4";
+            mountpoint = "/home";
+          };
+        };
+        raw = {
+          type = "lvm_lv";
+          size = "10M";
+        };
+      };
     };
   };
 }
diff --git a/example/lvm-raid.nix b/example/lvm-raid.nix
index 48930ec..3c5ee69 100644
--- a/example/lvm-raid.nix
+++ b/example/lvm-raid.nix
@@ -1,66 +1,74 @@
 {
-  type = "devices";
-  content = {
+  disk = {
     vdb = {
-      type = "table";
-      format = "gpt";
-      partitions = [
-        {
-          type = "partition";
-          part-type = "primary";
-          start = "0%";
-          end = "100%";
-          content = {
-            type = "lvm_pv";
-            vg = "pool";
-          };
-        }
-      ];
+      type = "disk";
+      device = "/dev/vdb";
+      content = {
+        type = "table";
+        format = "gpt";
+        partitions = [
+          {
+            type = "partition";
+            name = "primary";
+            start = "0%";
+            end = "100%";
+            content = {
+              type = "lvm_pv";
+              vg = "pool";
+            };
+          }
+        ];
+      };
     };
     vdc = {
-      type = "table";
-      format = "gpt";
-      partitions = [
-        {
-          type = "partition";
-          part-type = "primary";
-          start = "0%";
-          end = "100%";
-          content = {
-            type = "lvm_pv";
-            vg = "pool";
-          };
-        }
-      ];
+      type = "disk";
+      device = "/dev/vdc";
+      content = {
+        type = "table";
+        format = "gpt";
+        partitions = [
+          {
+            type = "partition";
+            name = "primary";
+            start = "0%";
+            end = "100%";
+            content = {
+              type = "lvm_pv";
+              vg = "pool";
+            };
+          }
+        ];
+      };
     };
+  };
+  lvm_vg = {
     pool = {
       type = "lvm_vg";
-        lvs = {
-          root = {
-            type = "lvm_lv";
-            size = "100M";
+      lvs = {
+        root = {
+          type = "lvm_lv";
+          size = "100M";
+          lvm_type = "mirror";
+          content = {
+            type = "filesystem";
+            format = "ext4";
             mountpoint = "/";
-            lvm_type = "mirror";
-            content = {
-              type = "filesystem";
-              format = "ext4";
-              mountpoint = "/";
-              options = [
-                "defaults"
-              ];
-            };
-          };
-          home = {
-            type = "lvm_lv";
-            size = "10M";
-            lvm_type = "raid0";
-            content = {
-              type = "filesystem";
-              format = "ext4";
-              mountpoint = "/home";
-            };
+            options = [
+              "defaults"
+            ];
           };
         };
+        home = {
+          type = "lvm_lv";
+          size = "10M";
+          lvm_type = "raid0";
+          content = {
+            type = "filesystem";
+            format = "ext4";
+            mountpoint = "/home";
+          };
+        };
+      };
     };
   };
 }
diff --git a/example/mdadm.nix b/example/mdadm.nix
index cb0ad91..094499d 100644
--- a/example/mdadm.nix
+++ b/example/mdadm.nix
@@ -1,39 +1,47 @@
-# usage: nix-instantiate --eval --json --strict example/config.nix | jq .
 {
-  type = "devices";
-  content = {
+  disk = {
     vdb = {
-      type = "table";
-      format = "gpt";
-      partitions = [
-        {
-          type = "partition";
-          part-type = "primary";
-          start = "1MiB";
-          end = "100%";
-          content = {
-            type = "mdraid";
-            name = "raid1";
-          };
-        }
-      ];
+      type = "disk";
+      device = "/dev/vdb";
+      content = {
+        type = "table";
+        format = "gpt";
+        partitions = [
+          {
+            type = "partition";
+            name = "mdadm";
+            start = "1MiB";
+            end = "100%";
+            content = {
+              type = "mdraid";
+              name = "raid1";
+            };
+          }
+        ];
+      };
     };
     vdc = {
-      type = "table";
-      format = "gpt";
-      partitions = [
-        {
-          type = "partition";
-          part-type = "primary";
-          start = "1MiB";
-          end = "100%";
-          content = {
-            type = "mdraid";
-            name = "raid1";
-          };
-        }
-      ];
+      type = "disk";
+      device = "/dev/vdc";
+      content = {
+        type = "table";
+        format = "gpt";
+        partitions = [
+          {
+            type = "partition";
+            name = "mdadm";
+            start = "1MiB";
+            end = "100%";
+            content = {
+              type = "mdraid";
+              name = "raid1";
+            };
+          }
+        ];
+      };
     };
+  };
+  mdadm = {
     raid1 = {
       type = "mdadm";
       level = 1;
@@ -43,7 +51,7 @@
         partitions = [
           {
             type = "partition";
-            part-type = "primary";
+            name = "primary";
             start = "1MiB";
             end = "100%";
             content = {
diff --git a/example/zfs-over-legacy.nix b/example/zfs-over-legacy.nix
index 8f5a8bc..81a5975 100644
--- a/example/zfs-over-legacy.nix
+++ b/example/zfs-over-legacy.nix
@@ -1,41 +1,46 @@
 {
-  type = "devices";
-  content = {
+  disk = {
     vdb = {
-      type = "table";
-      format = "gpt";
-      partitions = [
-        {
-          type = "partition";
-          # leave space for the grub aka BIOS boot
-          start = "0%";
-          end = "100%";
-          part-type = "primary";
-          bootable = true;
-          content = {
-            type = "filesystem";
-            format = "ext4";
-            mountpoint = "/";
-          };
-        }
-      ];
+      type = "disk";
+      device = "/dev/vdb";
+      content = {
+        type = "table";
+        format = "gpt";
+        partitions = [
+          {
+            type = "partition";
+            start = "0%";
+            end = "100%";
+            name = "primary";
+            bootable = true;
+            content = {
+              type = "filesystem";
+              format = "ext4";
+              mountpoint = "/";
+            };
+          }
+        ];
+      };
     };
     vdc = {
-      type = "zfs";
-      pool = "zroot";
+      type = "disk";
+      device = "/dev/vdc";
+      content = {
+        type = "zfs";
+        pool = "zroot";
+      };
     };
+  };
+  zpool = {
     zroot = {
       type = "zpool";
-      mountpoint = "/";
-
-      datasets = [
-        {
-          type = "zfs_filesystem";
-          name = "zfs_fs";
+      datasets = {
+        zfs_fs = {
+          zfs_type = "filesystem";
           mountpoint = "/zfs_fs";
           options."com.sun:auto-snapshot" = "true";
-        }
-      ];
+        };
+      };
     };
   };
 }
diff --git a/example/zfs.nix b/example/zfs.nix
index 60e4700..16da367 100644
--- a/example/zfs.nix
+++ b/example/zfs.nix
@@ -1,14 +1,23 @@
 {
-  type = "devices";
-  content = {
+  disk = {
     vdb = {
-      type = "zfs";
-      pool = "zroot";
+      type = "disk";
+      device = "/dev/vdb";
+      content = {
+        type = "zfs";
+        pool = "zroot";
+      };
     };
     vdc = {
-      type = "zfs";
-      pool = "zroot";
+      type = "disk";
+      device = "/dev/vdc";
+      content = {
+        type = "zfs";
+        pool = "zroot";
+      };
     };
+  };
+  zpool = {
     zroot = {
       type = "zpool";
       mode = "mirror";
@@ -18,35 +27,31 @@
       };
       mountpoint = "/";
 
-      datasets = [
-        {
-          type = "zfs_filesystem";
-          name = "zfs_fs";
+      datasets = {
+        zfs_fs = {
+          zfs_type = "filesystem";
           mountpoint = "/zfs_fs";
           options."com.sun:auto-snapshot" = "true";
-        }
-        {
-          type = "zfs_filesystem";
-          name = "zfs_unmounted_fs";
+        };
+        zfs_unmounted_fs = {
+          zfs_type = "filesystem";
           options.mountpoint = "none";
-        }
-        {
-          type = "zfs_filesystem";
-          name = "zfs_legacy_fs";
+        };
+        zfs_legacy_fs = {
+          zfs_type = "filesystem";
           options.mountpoint = "legacy";
           mountpoint = "/zfs_legacy_fs";
-        }
-        {
-          type = "zfs_volume";
-          name = "zfs_testvolume";
+        };
+        zfs_testvolume = {
+          zfs_type = "volume";
           size = "10M";
           content = {
             type = "filesystem";
             format = "ext4";
             mountpoint = "/ext4onzfs";
           };
-        }
-      ];
+        };
+      };
     };
   };
 }
diff --git a/tests/complex.nix b/tests/complex.nix
new file mode 100644
index 0000000..3fa861e
--- /dev/null
+++ b/tests/complex.nix
@@ -0,0 +1,20 @@
+{ pkgs ? (import <nixpkgs> { })
+, makeDiskoTest ? (pkgs.callPackage ./lib.nix { }).makeDiskoTest
+}:
+makeDiskoTest {
+  disko-config = import ../example/complex.nix;
+  extraTestScript = ''
+    machine.succeed("test -b /dev/zroot/zfs_testvolume");
+    machine.succeed("test -b /dev/md/raid1p1");
+
+
+    machine.succeed("mountpoint /mnt");
+    machine.succeed("mountpoint /mnt/zfs_fs");
+    machine.succeed("mountpoint /mnt/zfs_legacy_fs");
+    machine.succeed("mountpoint /mnt/ext4onzfs");
+    machine.succeed("mountpoint /mnt/ext4_on_lvm");
+  '';
+  extraConfig = {
+    boot.kernelModules = [ "dm-raid" "dm-mirror" ];
+  };
+}
diff --git a/tests/lib.nix b/tests/lib.nix
index 2ec42e6..0bcba2b 100644
--- a/tests/lib.nix
+++ b/tests/lib.nix
@@ -17,7 +17,7 @@
         };
       tsp-create = pkgs.writeScript "create" ((pkgs.callPackage ../. { }).create disko-config);
       tsp-mount = pkgs.writeScript "mount" ((pkgs.callPackage ../. { }).mount disko-config);
-      num-disks = builtins.length (builtins.filter (x: builtins.match "vd." x == [ ]) (lib.attrNames disko-config.content));
+      num-disks = builtins.length (lib.attrNames disko-config.disk);
     in
     makeTest' {
       name = "disko";
diff --git a/types.nix b/types.nix
new file mode 100644
index 0000000..e7dcf60
--- /dev/null
+++ b/types.nix
@@ -0,0 +1,1058 @@
+{ pkgs ? import <nixpkgs> {} }:
+with pkgs.lib;
+with builtins;
+
+rec {
+
+  diskoLib = {
+    # like types.oneOf but instead of a list takes an attrset
+    # uses the field "type" to find the correct type in the attrset
+    subType = typeAttr: mkOptionType rec {
+      name = "subType";
+      description = "one of ${attrNames typeAttr}";
+      check = x: typeAttr.${x.type}.check x;
+      merge = loc: defs:
+        foldl' (res: def: typeAttr.${def.value.type}.merge loc [def]) {} defs;
+      nestedTypes = typeAttr;
+    };
+
+    # option for valid contents of partitons (basically like devices, but without tables)
+    partitionType = mkOption {
+      type = types.nullOr (diskoLib.subType { inherit btrfs filesystem zfs mdraid luks lvm_pv; });
+      default = null;
+    };
+
+    # option for valid contents of devices
+    deviceType = mkOption {
+      type = types.nullOr (diskoLib.subType { inherit table btrfs filesystem zfs mdraid luks lvm_pv; });
+      default = null;
+    };
+
+    /* deepMergeMap takes a function and a list of attrsets and deep merges them
+
+       deepMergeMap :: -> (AttrSet -> AttrSet ) -> [ AttrSet ] -> Attrset
+
+       Example:
+         deepMergeMap (x: x.t = "test") [ { x = { y = 1; z = 3; }; } { x = { 123 = 234; }; } ]
+         => { x = { y = 1; z = 3; 123 = 234; t = "test"; }; }
+    */
+    deepMergeMap = f: listOfAttrs:
+      foldr (attr: acc: (recursiveUpdate acc (f attr))) {} listOfAttrs;
+
+    /* get a device and an index to get the matching device name
+
+       deviceNumbering :: str -> int -> str
+
+       Example:
+       deviceNumbering "/dev/sda" 3
+       => "/dev/sda3"
+
+       deviceNumbering "/dev/disk/by-id/xxx" 2
+       => "/dev/disk/by-id/xxx-part2"
+    */
+    deviceNumbering = dev: index:
+      let
+        schemas = {
+          dev__da = dev + toString index; # /dev/{s,v}da style
+          dev_disk = "${dev}-part${toString index}"; # /dev/disk/by-id/xxx style
+          dev_nvme = "${dev}n1p${toString index}"; # /dev/nvme0n1p1 style
+          dev_md = "${dev}p${toString index}"; # /dev/nvme0n1p1 style
+        };
+        detectSchema =
+          if match "/dev/[vs]d.*" dev != null then "dev__da" else
+          if match "/dev/disk/.*" dev != null then "dev_disk" else
+          if match "/dev/nvme.*" dev != null then "dev_nvme" else
+          if match "/dev/md/.*" dev != null then "dev_md" else
+          abort "${dev} seems not to be a supported disk format";
+      in schemas.${detectSchema};
+
+    /* Given a attrset of dependencies and a devices attrset
+       returns a sorted list by dependencies. aborts if a loop is found
+
+       sortDevicesByDependencies :: AttrSet -> AttrSet -> [ [ str str ] ]
+    */
+    sortDevicesByDependencies = dependencies: devices:
+      let
+        dependsOn = a: b:
+          elem a (attrByPath b [] dependencies);
+        maybeSortedDevices = toposort dependsOn (diskoLib.deviceList devices);
+      in
+        if (hasAttr "cycle" maybeSortedDevices) then
+          abort "detected a cycle in your disk setup: ${maybeSortedDevices.cycle}"
+        else
+          maybeSortedDevices.result;
+
+    /* Takes a devices attrSet and returns it as a list
+
+       deviceList :: AttrSet -> [ [ str str ] ]
+
+       Example:
+         deviceList { zfs.pool1 = {}; zfs.pool2 = {}; mdadm.raid1 = {}; }
+         => [ [ "zfs" "pool1" ] [ "zfs" "pool2" ] [ "mdadm" "raid1" ] ]
+    */
+    deviceList = devices:
+      concatLists (mapAttrsToList (n: v: (map (x: [ n x ]) (attrNames v))) devices);
+
+    /* Takes either a string or null and returns the string or an empty string
+
+       maybeStr :: Either (str null) -> str
+
+       Example:
+         maybeStr null
+         => ""
+         maybeSTr "hello world"
+         => "hello world"
+    */
+    maybeStr = x: optionalString (!isNull x) x;
+  };
+
+  optionTypes = rec {
+    # POSIX.1‐2017, 3.281 Portable Filename
+    filename = mkOptionType {
+      name = "POSIX portable filename";
+      check = x: isString x && builtins.match "[0-9A-Za-z._][0-9A-Za-z._-]*" x != null;
+      merge = mergeOneOption;
+    };
+
+    # POSIX.1‐2017, 3.2 Absolute Pathname
+    absolute-pathname = mkOptionType {
+      name = "POSIX absolute pathname";
+      check = x: isString x && substring 0 1 x == "/" && pathname.check x;
+      merge = mergeOneOption;
+    };
+
+    # POSIX.1-2017, 3.271 Pathname
+    pathname = mkOptionType {
+      name = "POSIX pathname";
+      check = x:
+        let
+          # The filter is used to normalize paths, i.e. to remove duplicated and
+          # trailing slashes.  It also removes leading slashes, thus we have to
+          # check for "/" explicitly below.
+          xs = filter (s: stringLength s > 0) (splitString "/" x);
+        in
+          isString x && (x == "/" || (length xs > 0 && all filename.check xs));
+      merge = mergeOneOption;
+    };
+  };
+
+  /* topLevel type of the disko config, takes attrsets of disks mdadms zpools and lvm vgs.
+     exports create, mount, meta and config
+  */
+  topLevel = types.submodule ({ config, ... }: {
+    options = {
+      devices = {
+        disk = mkOption {
+          type = types.attrsOf disk;
+          default = {};
+        };
+        mdadm = mkOption {
+          type = types.attrsOf mdadm;
+          default = {};
+        };
+        zpool = mkOption {
+          type = types.attrsOf zpool;
+          default = {};
+        };
+        lvm_vg = mkOption {
+          type = types.attrsOf lvm_vg;
+          default = {};
+        };
+      };
+      meta = mkOption {
+        readOnly = true;
+        default = diskoLib.deepMergeMap (dev: dev._meta) (flatten (map attrValues [
+          config.devices.disk
+          config.devices.lvm_vg
+          config.devices.mdadm
+          config.devices.zpool
+        ])) // {
+          sortedDeviceList = diskoLib.sortDevicesByDependencies config.meta.dependencies config.devices;
+        };
+      };
+      create = mkOption {
+        readOnly = true;
+        type = types.str;
+        default = ''
+          set -efux
+          ${concatStrings (map (dev: attrByPath (dev ++ [ "_create" ]) "" config.devices) config.meta.sortedDeviceList)}
+        '';
+      };
+      mount = mkOption {
+        readOnly = true;
+        type = types.str;
+        default = let
+          fsMounts = diskoLib.deepMergeMap (dev: dev._mount.fs or {}) (flatten (map attrValues [
+            config.devices.disk
+            config.devices.lvm_vg
+            config.devices.mdadm
+            config.devices.zpool
+          ]));
+        in ''
+          set -efux
+          # first create the neccessary devices
+          ${concatStrings (map (dev: attrByPath (dev ++ [ "_mount" "dev" ]) "" config.devices) config.meta.sortedDeviceList)}
+
+          # and then mount the filesystems in alphabetical order
+          # attrValues returns values sorted by name.  This is important, because it
+          # ensures that "/" is processed before "/foo" etc.
+          ${concatStrings (attrValues fsMounts)}
+        '';
+      };
+      config = mkOption {
+        readOnly = true;
+        default = diskoLib.deepMergeMap (dev: dev._config) (flatten (map attrValues [
+          config.devices.disk
+          config.devices.lvm_vg
+          config.devices.mdadm
+          config.devices.zpool
+        ]));
+      };
+    };
+  });
+
+  btrfs = types.submodule ({ config, ... }: {
+    options = {
+      type = mkOption {
+        type = types.enum [ "btrfs" ];
+        internal = true;
+      };
+      mountOptions = mkOption {
+        type = types.listOf types.str;
+        default = [];
+      };
+      subvolumes = mkOption {
+        type = types.listOf optionTypes.pathname;
+        default = [];
+      };
+      mountpoint = mkOption {
+        type = optionTypes.absolute-pathname;
+      };
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev: {
+        };
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo types.str;
+        default = dev: ''
+          mkfs.btrfs ${dev}
+          ${optionalString (!isNull config.subvolumes or null) ''
+            MNTPOINT=$(mktemp -d)
+            (
+              mount ${dev} "$MNTPOINT"
+              trap 'umount $MNTPOINT; rm -rf $MNTPOINT' EXIT
+              ${concatMapStringsSep "\n" (subvolume: "btrfs subvolume create \"$MNTPOINT\"/${subvolume}") config.subvolumes}
+            )
+          ''}
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev: {
+          fs.${config.mountpoint} = ''
+            if ! findmnt ${dev} "/mnt${config.mountpoint}" > /dev/null 2>&1; then
+              mount ${dev} "/mnt${config.mountpoint}" \
+              ${concatStringsSep " " config.mountOptions} \
+              -o X-mount.mkdir
+            fi
+          '';
+        };
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default = dev: {
+          fileSystems.${config.mountpoint} = {
+            device = dev;
+            fsType = "btrfs";
+          };
+        };
+      };
+    };
+  });
+
+  filesystem = types.submodule ({ config, ... }: {
+    options = {
+      type = mkOption {
+        type = types.enum [ "filesystem" ];
+        internal = true;
+      };
+      extraArgs = mkOption {
+        type = types.str;
+        default = "";
+      };
+      mountOptions = mkOption {
+        type = types.listOf types.str;
+        default = [];
+      };
+      options = mkOption {
+        type = types.listOf types.str;
+        default = [];
+      };
+      mountpoint = mkOption {
+        type = optionTypes.absolute-pathname;
+      };
+      format = mkOption {
+        type = types.str;
+      };
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev: {
+        };
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo types.str;
+        default = dev: ''
+          mkfs.${config.format} \
+            ${config.extraArgs} \
+            ${dev}
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev: {
+          fs.${config.mountpoint} = ''
+            if ! findmnt ${dev} "/mnt${config.mountpoint}" > /dev/null 2>&1; then
+              mount ${dev} "/mnt${config.mountpoint}" \
+              ${toString config.mountOptions} \
+              -o X-mount.mkdir
+            fi
+          '';
+        };
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default = dev: {
+          fileSystems.${config.mountpoint} = {
+            device = dev;
+            fsType = config.format;
+          };
+        };
+      };
+    };
+  });
+
+  table = types.submodule ({ config, ... }: {
+    options = {
+      type = mkOption {
+        type = types.enum [ "table" ];
+        internal = true;
+      };
+      format = mkOption {
+        type = types.enum [ "gpt" "msdos" ];
+        default = "gpt";
+      };
+      partitions = mkOption {
+        type = types.listOf partition;
+        default = [];
+      };
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev:
+          diskoLib.deepMergeMap (partition: partition._meta dev) config.partitions;
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo types.str;
+        default = dev: ''
+          parted -s ${dev} mklabel ${config.format}
+          ${concatMapStrings (partition: partition._create dev config.format) config.partitions}
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev:
+          let
+            partMounts = diskoLib.deepMergeMap (partition: partition._mount dev) config.partitions;
+          in {
+            dev = ''
+              ${concatStrings (map (x: x.dev or "") (attrValues partMounts))}
+            '';
+            fs = partMounts.fs or {};
+        };
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default = dev:
+          diskoLib.deepMergeMap (partition: partition._config dev) config.partitions;
+      };
+    };
+  });
+
+  partition = types.submodule ({ config, ... }: {
+    options = {
+      type = mkOption {
+        type = types.enum [ "partition" ];
+        internal = true;
+      };
+      part-type = mkOption {
+        type = types.enum [ "primary" "logical" "extended" ];
+        default = "primary";
+      };
+      fs-type = mkOption {
+        type = types.nullOr (types.enum [ "btrfs" "ext2" "ext3" "ext4" "fat16" "fat32" "hfs" "hfs+" "linux-swap" "ntfs" "reiserfs" "udf" "xfs" ]);
+        default = null;
+      };
+      name = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+      };
+      start = mkOption {
+        type = types.str;
+        default = "0%";
+      };
+      end = mkOption {
+        type = types.str;
+        default = "100%";
+      };
+      index = mkOption {
+        type = types.int;
+        # TODO find a better way to get the index
+        default = toInt (head (match ".*entry ([[:digit:]]+)]" config._module.args.name));
+      };
+      flags = mkOption {
+        type = types.listOf types.str;
+        default = [];
+      };
+      bootable = mkOption {
+        type = types.bool;
+        default = false;
+      };
+      content = diskoLib.partitionType;
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev:
+          optionalAttrs (!isNull config.content) (config.content._meta dev);
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (types.functionTo types.str);
+        default = dev: type: ''
+          ${optionalString (type == "gpt") ''
+            parted -s ${dev} mkpart ${config.name} ${diskoLib.maybeStr config.fs-type} ${config.start} ${config.end}
+          ''}
+          ${optionalString (type == "msdos") ''
+            parted -s ${dev} mkpart ${config.part-type} ${diskoLib.maybeStr config.fs-type} ${diskoLib.maybeStr config.fs-type} ${config.start} ${config.end}
+          ''}
+          # ensure /dev/disk/by-path/..-partN exists before continuing
+          udevadm trigger --subsystem-match=block; udevadm settle
+          ${optionalString (config.bootable) ''
+            parted -s ${dev} set ${toString config.index} boot on
+          ''}
+          ${concatMapStringsSep "" (flag: ''
+            parted -s ${dev} set ${toString config.index} ${flag} on
+          '') config.flags}
+          ${optionalString (!isNull config.content) (config.content._create (diskoLib.deviceNumbering dev config.index))}
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev:
+          optionalAttrs (!isNull config.content) (config.content._mount (diskoLib.deviceNumbering dev config.index));
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default = dev:
+          optionalAttrs (!isNull config.content) (config.content._config (diskoLib.deviceNumbering dev config.index));
+      };
+    };
+  });
+
+  lvm_pv = types.submodule ({ config, ... }: {
+    options = {
+      type = mkOption {
+        type = types.enum [ "lvm_pv" ];
+        internal = true;
+      };
+      vg = mkOption {
+        type = types.str;
+      };
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev: {
+          dependencies.lvm_vg.${config.vg} = [ dev ];
+        };
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo types.str;
+        default = dev: ''
+          pvcreate ${dev}
+          LVMDEVICES_${config.vg}="''${LVMDEVICES_${config.vg}:-}${dev} "
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev:
+          {};
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default = dev: {};
+      };
+    };
+  });
+
+  lvm_vg = types.submodule ({ config, ... }: {
+    options = {
+      name = mkOption {
+        type = types.str;
+        default = config._module.args.name;
+      };
+      type = mkOption {
+        type = types.enum [ "lvm_vg" ];
+        internal = true;
+      };
+      lvs = mkOption {
+        type = types.attrsOf lvm_lv;
+        default = {};
+      };
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = (pkgs.formats.json {}).type;
+        default =
+          diskoLib.deepMergeMap (lv: lv._meta [ "lvm_vg" config.name ]) (attrValues config.lvs);
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.str;
+        default = ''
+          vgcreate ${config.name} $LVMDEVICES_${config.name}
+          ${concatMapStrings (lv: lv._create config.name) (attrValues config.lvs)}
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = (pkgs.formats.json {}).type;
+        default = let
+          lvMounts = diskoLib.deepMergeMap (lv: lv._mount config.name) (attrValues config.lvs);
+        in {
+          dev = ''
+            vgchange -a y
+            ${concatStrings (map (x: x.dev or "") (attrValues lvMounts))}
+          '';
+          fs = lvMounts.fs;
+        };
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default =
+          diskoLib.deepMergeMap (lv: lv._config config.name) (attrValues config.lvs);
+      };
+    };
+  });
+
+  lvm_lv = types.submodule ({ config, ... }: {
+    options = {
+      name = mkOption {
+        type = types.str;
+        default = config._module.args.name;
+      };
+      type = mkOption {
+        type = types.enum [ "lvm_lv" ];
+        default = "lvm_lv";
+        internal = true;
+      };
+      size = mkOption {
+        type = types.str; # TODO lvm size type
+      };
+      lvm_type = mkOption {
+        type = types.nullOr (types.enum [ "mirror" "raid0" "raid1" ]); # TODO add all types
+        default = null; # maybe there is always a default type?
+      };
+      extraArgs = mkOption {
+        type = types.str;
+        default = "";
+      };
+      content = diskoLib.partitionType;
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev:
+          optionalAttrs (!isNull config.content) (config.content._meta dev);
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo types.str;
+        default = vg: ''
+          lvcreate \
+            ${if hasInfix "%" config.size then "-l" else "-L"} ${config.size} \
+            -n ${config.name} \
+            ${optionalString (!isNull config.lvm_type) "--type=${config.lvm_type}"} \
+            ${config.extraArgs} \
+            ${vg}
+          ${optionalString (!isNull config.content) (config.content._create "/dev/${vg}/${config.name}")}
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = vg:
+          optionalAttrs (!isNull config.content) (config.content._mount "/dev/${vg}/${config.name}");
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default = dev:
+          optionalAttrs (!isNull config.content) (config.content._config dev);
+      };
+    };
+  });
+
+  zfs = types.submodule ({ config, ... }: {
+    options = {
+      type = mkOption {
+        type = types.enum [ "zfs" ];
+        internal = true;
+      };
+      pool = mkOption {
+        type = types.str;
+      };
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev: {
+          dependencies.zpool.${config.pool} = [ dev ];
+        };
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo types.str;
+        default = dev: ''
+          ZFSDEVICES_${config.pool}="''${ZFSDEVICES_${config.pool}:-}${dev} "
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev:
+          {};
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default = dev: {};
+      };
+    };
+  });
+
+  zpool = types.submodule ({ config, ... }: {
+    options = {
+      name = mkOption {
+        type = types.str;
+        default = config._module.args.name;
+      };
+      type = mkOption {
+        type = types.enum [ "zpool" ];
+        internal = true;
+      };
+      mode = mkOption {
+        type = types.str; # TODO zfs modes
+        default = "";
+      };
+      options = mkOption {
+        type = types.attrsOf types.str;
+        default = {};
+      };
+      rootFsOptions = mkOption {
+        type = types.attrsOf types.str;
+        default = {};
+      };
+      mountpoint = mkOption {
+        type = types.nullOr optionTypes.absolute-pathname;
+        default = null;
+      };
+      mountOptions = mkOption {
+        type = types.listOf types.str;
+        default = [];
+      };
+      datasets = mkOption {
+        type = types.attrsOf zfs_dataset;
+      };
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = (pkgs.formats.json {}).type;
+        default =
+          diskoLib.deepMergeMap (dataset: dataset._meta [ "zpool" config.name ]) (attrValues config.datasets);
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.str;
+        default = ''
+          zpool create ${config.name} \
+            ${config.mode} \
+            ${concatStringsSep " " (mapAttrsToList (n: v: "-o ${n}=${v}") config.options)} \
+            ${concatStringsSep " " (mapAttrsToList (n: v: "-O ${n}=${v}") config.rootFsOptions)} \
+            ''${ZFSDEVICES_${config.name}}
+          ${concatMapStrings (dataset: dataset._create config.name) (attrValues config.datasets)}
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = (pkgs.formats.json {}).type;
+        default = let
+          datasetMounts = diskoLib.deepMergeMap (dataset: dataset._mount config.name) (attrValues config.datasets);
+        in {
+          dev = ''
+            zpool list '${config.name}' >/dev/null 2>/dev/null || zpool import '${config.name}'
+            ${concatStrings (map (x: x.dev or "") (attrValues datasetMounts))}
+          '';
+          fs = datasetMounts.fs // optionalAttrs (!isNull config.mountpoint) {
+            ${config.mountpoint} = ''
+              if ! findmnt ${config.name} "/mnt${config.mountpoint}" > /dev/null 2>&1; then
+                mount ${config.name} "/mnt${config.mountpoint}" \
+                ${optionalString ((config.options.mountpoint or "") != "legacy") "-o zfsutil"} \
+                ${toString config.mountOptions} \
+                -o X-mount.mkdir \
+                -t zfs
+              fi
+            '';
+          };
+        };
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default =
+          recursiveUpdate
+            (diskoLib.deepMergeMap (dataset: dataset._config config.name) (attrValues config.datasets))
+            (optionalAttrs (!isNull config.mountpoint) {
+              fileSystems.${config.mountpoint} = {
+                device = config.name;
+                fsType = [ "zfs" ];
+              };
+            });
+      };
+    };
+  });
+
+  zfs_dataset = types.submodule ({ config, ... }: {
+    options = {
+      name = mkOption {
+        type = types.str;
+        default = config._module.args.name;
+      };
+      type = mkOption {
+        type = types.enum [ "zfs_dataset" ];
+        default = "zfs_dataset";
+      };
+      zfs_type = mkOption {
+        type = types.enum [ "filesystem" "volume" ];
+      };
+      options = mkOption {
+        type = types.attrsOf types.str;
+        default = {};
+      };
+      mountOptions = mkOption {
+        type = types.listOf types.str;
+        default = [];
+      };
+
+      # filesystem options
+      mountpoint = mkOption {
+        type = types.nullOr optionTypes.absolute-pathname;
+        default = null;
+      };
+
+      # volume options
+      size = mkOption {
+        type = types.nullOr types.str; # TODO size
+        default = null;
+      };
+
+      content = diskoLib.partitionType;
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev:
+          optionalAttrs (!isNull config.content) (config.content._meta dev);
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo types.str;
+        default = zpool: ''
+          zfs create ${zpool}/${config.name} \
+            ${concatStringsSep " " (mapAttrsToList (n: v: "-o ${n}=${v}") config.options)} \
+            ${optionalString (config.zfs_type == "volume") "-V ${config.size}"}
+          ${optionalString (config.zfs_type == "volume") ''
+            udevadm trigger --subsystem-match=block; udevadm settle
+            ${optionalString (!isNull config.content) (config.content._create "/dev/zvol/${zpool}/${config.name}")}
+          ''}
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = zpool:
+          optionalAttrs (config.zfs_type == "volume" && !isNull config.content) (config.content._mount "/dev/zvol/${zpool}/${config.name}") //
+            optionalAttrs (config.zfs_type == "filesystem" && config.options.mountpoint or "" != "none") { fs.${config.mountpoint} = ''
+              if ! findmnt ${zpool}/${config.name} "/mnt${config.mountpoint}" > /dev/null 2>&1; then
+                mount ${zpool}/${config.name} "/mnt${config.mountpoint}" \
+                -o X-mount.mkdir \
+                ${toString config.mountOptions} \
+                ${optionalString ((config.options.mountpoint or "") != "legacy") "-o zfsutil"} \
+                -t zfs
+              fi
+            ''; };
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default = zpool:
+          optionalAttrs (config.zfs_type == "volume" && !isNull config.content) (config.content._config "/dev/zvol/${zpool}/${config.name}") //
+            optionalAttrs (config.zfs_type == "filesystem" && config.options.mountpoint or "" != "none") {
+              fileSystems.${config.mountpoint} = {
+                device = "${zpool}/${config.name}";
+                fsType = [ "zfs" ];
+              };
+            };
+      };
+    };
+  });
+
+  mdadm = types.submodule ({ config, ... }: {
+    options = {
+      name = mkOption {
+        type = types.str;
+        default = config._module.args.name;
+      };
+      type = mkOption {
+        type = types.enum [ "mdadm" ];
+        default = "mdadm";
+      };
+      level = mkOption {
+        type = types.int;
+        default = 1;
+      };
+      content = diskoLib.deviceType;
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = (pkgs.formats.json {}).type;
+        default =
+          optionalAttrs (!isNull config.content) (config.content._meta [ "mdadm" config.name ]);
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.str;
+        default = ''
+          echo 'y' | mdadm --create /dev/md/${config.name} \
+            --level=${toString config.level} \
+            --raid-devices=''${RAIDDEVICES_N_${config.name}} \
+            ''${RAIDDEVICES_${config.name}}
+          udevadm trigger --subsystem-match=block; udevadm settle
+          ${optionalString (!isNull config.content) (config.content._create "/dev/md/${config.name}")}
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = (pkgs.formats.json {}).type;
+        default =
+          optionalAttrs (!isNull config.content) (config.content._mount "/dev/md/${config.name}");
+        # TODO we probably need to assemble the mdadm somehow
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default =
+          optionalAttrs (!isNull config.content) (config.content._config "/dev/md/${config.name}");
+      };
+    };
+  });
+
+  mdraid = types.submodule ({ config, ... }: {
+    options = {
+      type = mkOption {
+        type = types.enum [ "mdraid" ];
+      };
+
+      name = mkOption {
+        type = types.str;
+      };
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev: {
+          dependencies.mdadm.${config.name} = [ dev ];
+        };
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo types.str;
+        default = dev: ''
+          RAIDDEVICES_N_${config.name}=$((''${RAIDDEVICES_N_${config.name}:-0}+1))
+          RAIDDEVICES_${config.name}="''${RAIDDEVICES_${config.name}:-}${dev} "
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev:
+          {};
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default = dev: {};
+      };
+    };
+  });
+
+  luks = types.submodule ({ config, ... }: {
+    options = {
+      type = mkOption {
+        type = types.enum [ "luks" ];
+      };
+      name = mkOption {
+        type = types.str;
+      };
+      keyFile = mkOption {
+        type = types.nullOr optionTypes.absolute-pathname;
+        default = null;
+      };
+      extraArgs = mkOption {
+        type = types.listOf types.str;
+        default = [];
+      };
+      content = diskoLib.deviceType;
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev:
+          optionalAttrs (!isNull config.content) (config.content._meta dev);
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo types.str;
+        default = dev: ''
+          cryptsetup -q luksFormat ${dev} ${diskoLib.maybeStr config.keyFile} ${toString config.extraArgs}
+          cryptsetup luksOpen ${dev} ${config.name} ${optionalString (!isNull config.keyFile) "--key-file ${config.keyFile}"}
+          ${optionalString (!isNull config.content) (config.content._create "/dev/mapper/${config.name}")}
+        '';
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.functionTo (pkgs.formats.json {}).type;
+        default = dev:
+          let
+            contentMount = config.content._mount "/dev/mapper/${config.name}";
+          in
+            {
+              dev = ''
+                cryptsetup status ${config.name} >/dev/null 2>/dev/null ||
+                  cryptsetup luksOpen ${dev} ${config.name} ${optionalString (!isNull config.keyFile) "--key-file ${config.keyFile}"}
+                ${optionalString (!isNull config.content) contentMount.dev or ""}
+              '';
+              fs = optionalAttrs (!isNull config.content) contentMount.fs or {};
+            };
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default = dev:
+          recursiveUpdate {
+            # TODO do we need this always in initrd and only there?
+            boot.initrd.luks.devices.${config.name}.device = dev;
+          } (optionalAttrs (!isNull config.content) (config.content._config "/dev/mapper/${config.name}"));
+      };
+    };
+  });
+
+  disk = types.submodule ({ config, ... }: {
+    options = {
+      name = mkOption {
+        type = types.str;
+        default = config._module.args.name;
+      };
+      type = mkOption {
+        type = types.enum [ "disk" ];
+      };
+      device = mkOption {
+        type = optionTypes.absolute-pathname; # TODO check if subpath of /dev ?
+      };
+      content = diskoLib.deviceType;
+      _meta = mkOption {
+        internal = true;
+        readOnly = true;
+        type = (pkgs.formats.json {}).type;
+        default =
+          optionalAttrs (!isNull config.content) (config.content._meta [ "disk" config.device ]);
+      };
+      _create = mkOption {
+        internal = true;
+        readOnly = true;
+        type = types.str;
+        default = config.content._create config.device;
+      };
+      _mount = mkOption {
+        internal = true;
+        readOnly = true;
+        type = (pkgs.formats.json {}).type;
+        default =
+          optionalAttrs (!isNull config.content) (config.content._mount config.device);
+      };
+      _config = mkOption {
+        internal = true;
+        readOnly = true;
+        default =
+          optionalAttrs (!isNull config.content) (config.content._config config.device);
+      };
+    };
+  });
+}