334 lines
9.6 KiB
Nix
334 lines
9.6 KiB
Nix
# Note: This is a private API, internal to NixOS. Its interface is subject
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# to change without notice.
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#
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# The result of this builder is two disk images:
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#
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# * `boot` - a small disk formatted with FAT to be used for /boot. FAT is
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# chosen to support EFI.
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# * `root` - a larger disk with a zpool taking the entire disk.
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#
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# This two-disk approach is taken to satisfy ZFS's requirements for
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# autoexpand.
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#
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# # Why doesn't autoexpand work with ZFS in a partition?
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#
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# When ZFS owns the whole disk doesn’t really use a partition: it has
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# a marker partition at the start and a marker partition at the end of
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# the disk.
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#
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# If ZFS is constrained to a partition, ZFS leaves expanding the partition
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# up to the user. Obviously, the user may not choose to do so.
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#
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# Once the user expands the partition, calling zpool online -e expands the
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# vdev to use the whole partition. It doesn’t happen automatically
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# presumably because zed doesn’t get an event saying it’s partition grew,
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# whereas it can and does get an event saying the whole disk it is on is
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# now larger.
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{ lib
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, pkgs
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, # The NixOS configuration to be installed onto the disk image.
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config
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, # size of the FAT boot disk, in megabytes.
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bootSize ? 1024
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, # The size of the root disk, in megabytes.
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rootSize ? 2048
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, # The name of the ZFS pool
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rootPoolName ? "tank"
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, # zpool properties
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rootPoolProperties ? {
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autoexpand = "on";
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}
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, # pool-wide filesystem properties
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rootPoolFilesystemProperties ? {
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acltype = "posixacl";
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atime = "off";
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compression = "on";
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mountpoint = "legacy";
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xattr = "sa";
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}
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, # datasets, with per-attribute options:
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# mount: (optional) mount point in the VM
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# properties: (optional) ZFS properties on the dataset, like filesystemProperties
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# Notes:
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# 1. datasets will be created from shorter to longer names as a simple topo-sort
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# 2. you should define a root's dataset's mount for `/`
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datasets ? { }
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, # The files and directories to be placed in the target file system.
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# This is a list of attribute sets {source, target} where `source'
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# is the file system object (regular file or directory) to be
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# grafted in the file system at path `target'.
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contents ? []
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, # The initial NixOS configuration file to be copied to
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# /etc/nixos/configuration.nix. This configuration will be embedded
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# inside a configuration which includes the described ZFS fileSystems.
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configFile ? null
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, # Shell code executed after the VM has finished.
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postVM ? ""
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, name ? "nixos-disk-image"
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, # Disk image format, one of qcow2, qcow2-compressed, vdi, vpc, raw.
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format ? "raw"
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, # Include a copy of Nixpkgs in the disk image
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includeChannel ? true
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}:
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let
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formatOpt = if format == "qcow2-compressed" then "qcow2" else format;
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compress = lib.optionalString (format == "qcow2-compressed") "-c";
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filenameSuffix = "." + {
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qcow2 = "qcow2";
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vdi = "vdi";
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vpc = "vhd";
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raw = "img";
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}.${formatOpt} or formatOpt;
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bootFilename = "nixos.boot${filenameSuffix}";
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rootFilename = "nixos.root${filenameSuffix}";
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# FIXME: merge with channel.nix / make-channel.nix.
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channelSources =
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let
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nixpkgs = lib.cleanSource pkgs.path;
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in
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pkgs.runCommand "nixos-${config.system.nixos.version}" {} ''
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mkdir -p $out
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cp -prd ${nixpkgs.outPath} $out/nixos
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chmod -R u+w $out/nixos
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if [ ! -e $out/nixos/nixpkgs ]; then
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ln -s . $out/nixos/nixpkgs
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fi
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rm -rf $out/nixos/.git
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echo -n ${config.system.nixos.versionSuffix} > $out/nixos/.version-suffix
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'';
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closureInfo = pkgs.closureInfo {
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rootPaths = [ config.system.build.toplevel ]
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++ (lib.optional includeChannel channelSources);
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};
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modulesTree = pkgs.aggregateModules
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(with config.boot.kernelPackages; [ kernel zfs ]);
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tools = lib.makeBinPath (
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with pkgs; [
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config.system.build.nixos-enter
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config.system.build.nixos-install
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dosfstools
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e2fsprogs
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gptfdisk
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nix
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parted
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util-linux
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zfs
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]
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);
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hasDefinedMount = disk: ((disk.mount or null) != null);
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stringifyProperties = prefix: properties: lib.concatStringsSep " \\\n" (
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lib.mapAttrsToList
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(
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property: value: "${prefix} ${lib.escapeShellArg property}=${lib.escapeShellArg value}"
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)
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properties
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);
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featuresToProperties = features:
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lib.listToAttrs
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(builtins.map (feature: {
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name = "feature@${feature}";
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value = "enabled";
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}) features);
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createDatasets =
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let
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datasetlist = lib.mapAttrsToList lib.nameValuePair datasets;
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sorted = lib.sort (left: right: (lib.stringLength left.name) < (lib.stringLength right.name)) datasetlist;
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cmd = { name, value }:
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let
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properties = stringifyProperties "-o" (value.properties or {});
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in
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"zfs create -p ${properties} ${name}";
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in
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lib.concatMapStringsSep "\n" cmd sorted;
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mountDatasets =
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let
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datasetlist = lib.mapAttrsToList lib.nameValuePair datasets;
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mounts = lib.filter ({ value, ... }: hasDefinedMount value) datasetlist;
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sorted = lib.sort (left: right: (lib.stringLength left.value.mount) < (lib.stringLength right.value.mount)) mounts;
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cmd = { name, value }:
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''
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mkdir -p /mnt${lib.escapeShellArg value.mount}
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mount -t zfs ${name} /mnt${lib.escapeShellArg value.mount}
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'';
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in
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lib.concatMapStringsSep "\n" cmd sorted;
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unmountDatasets =
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let
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datasetlist = lib.mapAttrsToList lib.nameValuePair datasets;
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mounts = lib.filter ({ value, ... }: hasDefinedMount value) datasetlist;
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sorted = lib.sort (left: right: (lib.stringLength left.value.mount) > (lib.stringLength right.value.mount)) mounts;
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cmd = { name, value }:
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''
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umount /mnt${lib.escapeShellArg value.mount}
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'';
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in
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lib.concatMapStringsSep "\n" cmd sorted;
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fileSystemsCfgFile =
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let
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mountable = lib.filterAttrs (_: value: hasDefinedMount value) datasets;
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in
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pkgs.runCommand "filesystem-config.nix" {
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buildInputs = with pkgs; [ jq nixpkgs-fmt ];
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filesystems = builtins.toJSON {
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fileSystems = lib.mapAttrs'
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(
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dataset: attrs:
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{
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name = attrs.mount;
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value = {
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fsType = "zfs";
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device = "${dataset}";
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};
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}
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)
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mountable;
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};
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passAsFile = [ "filesystems" ];
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} ''
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(
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echo "builtins.fromJSON '''"
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jq . < "$filesystemsPath"
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echo "'''"
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) > $out
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nixpkgs-fmt $out
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'';
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mergedConfig =
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if configFile == null
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then fileSystemsCfgFile
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else
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pkgs.runCommand "configuration.nix" {
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buildInputs = with pkgs; [ nixpkgs-fmt ];
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}
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''
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(
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echo '{ imports = ['
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printf "(%s)\n" "$(cat ${fileSystemsCfgFile})";
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printf "(%s)\n" "$(cat ${configFile})";
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echo ']; }'
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) > $out
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nixpkgs-fmt $out
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'';
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image = (
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pkgs.vmTools.override {
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rootModules =
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[ "zfs" "9p" "9pnet_virtio" "virtio_pci" "virtio_blk" ] ++
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(pkgs.lib.optional pkgs.stdenv.hostPlatform.isx86 "rtc_cmos");
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kernel = modulesTree;
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}
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).runInLinuxVM (
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pkgs.runCommand name
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{
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QEMU_OPTS = "-drive file=$bootDiskImage,if=virtio,cache=unsafe,werror=report"
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+ " -drive file=$rootDiskImage,if=virtio,cache=unsafe,werror=report";
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preVM = ''
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PATH=$PATH:${pkgs.qemu_kvm}/bin
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mkdir $out
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bootDiskImage=boot.raw
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qemu-img create -f raw $bootDiskImage ${toString bootSize}M
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rootDiskImage=root.raw
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qemu-img create -f raw $rootDiskImage ${toString rootSize}M
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'';
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postVM = ''
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${if formatOpt == "raw" then ''
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mv $bootDiskImage $out/${bootFilename}
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mv $rootDiskImage $out/${rootFilename}
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'' else ''
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${pkgs.qemu}/bin/qemu-img convert -f raw -O ${formatOpt} ${compress} $bootDiskImage $out/${bootFilename}
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${pkgs.qemu}/bin/qemu-img convert -f raw -O ${formatOpt} ${compress} $rootDiskImage $out/${rootFilename}
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''}
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bootDiskImage=$out/${bootFilename}
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rootDiskImage=$out/${rootFilename}
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set -x
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${postVM}
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'';
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} ''
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export PATH=${tools}:$PATH
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set -x
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cp -sv /dev/vda /dev/sda
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cp -sv /dev/vda /dev/xvda
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parted --script /dev/vda -- \
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mklabel gpt \
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mkpart no-fs 1MiB 2MiB \
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set 1 bios_grub on \
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align-check optimal 1 \
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mkpart ESP fat32 2MiB -1MiB \
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align-check optimal 2 \
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print
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sfdisk --dump /dev/vda
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zpool create \
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${stringifyProperties " -o" rootPoolProperties} \
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${stringifyProperties " -O" rootPoolFilesystemProperties} \
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${rootPoolName} /dev/vdb
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parted --script /dev/vdb -- print
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${createDatasets}
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${mountDatasets}
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mkdir -p /mnt/boot
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mkfs.vfat -n ESP /dev/vda2
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mount /dev/vda2 /mnt/boot
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mount
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# Install a configuration.nix
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mkdir -p /mnt/etc/nixos
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# `cat` so it is mutable on the fs
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cat ${mergedConfig} > /mnt/etc/nixos/configuration.nix
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export NIX_STATE_DIR=$TMPDIR/state
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nix-store --load-db < ${closureInfo}/registration
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nixos-install \
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--root /mnt \
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--no-root-passwd \
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--system ${config.system.build.toplevel} \
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--substituters "" \
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${lib.optionalString includeChannel ''--channel ${channelSources}''}
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df -h
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umount /mnt/boot
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${unmountDatasets}
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zpool export ${rootPoolName}
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''
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);
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in
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image
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