401 lines
14 KiB
Nix
401 lines
14 KiB
Nix
{ pkgs
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, lib
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, # The NixOS configuration to be installed onto the disk image.
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config
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, # The size of the disk, in megabytes.
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# if "auto" size is calculated based on the contents copied to it and
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# additionalSpace is taken into account.
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diskSize ? "auto"
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, # additional disk space to be added to the image if diskSize "auto"
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# is used
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additionalSpace ? "512M"
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, # size of the boot partition, is only used if partitionTableType is
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# either "efi" or "hybrid"
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# This will be undersized slightly, as this is actually the offset of
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# the end of the partition. Generally it will be 1MiB smaller.
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bootSize ? "256M"
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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, mode, user, group} where
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# `source' is the file system object (regular file or directory) to be
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# grafted in the file system at path `target', `mode' is a string containing
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# the permissions that will be set (ex. "755"), `user' and `group' are the
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# user and group name that will be set as owner of the files.
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# `mode', `user', and `group' are optional.
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# When setting one of `user' or `group', the other needs to be set too.
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contents ? []
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, # Type of partition table to use; either "legacy", "efi", or "none".
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# For "efi" images, the GPT partition table is used and a mandatory ESP
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# partition of reasonable size is created in addition to the root partition.
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# For "legacy", the msdos partition table is used and a single large root
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# partition is created.
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# For "legacy+gpt", the GPT partition table is used, a 1MiB no-fs partition for
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# use by the bootloader is created, and a single large root partition is
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# created.
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# For "hybrid", the GPT partition table is used and a mandatory ESP
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# partition of reasonable size is created in addition to the root partition.
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# Also a legacy MBR will be present.
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# For "none", no partition table is created. Enabling `installBootLoader`
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# most likely fails as GRUB will probably refuse to install.
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partitionTableType ? "legacy"
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, # The root file system type.
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fsType ? "ext4"
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, # Filesystem label
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label ? "nixos"
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, # The initial NixOS configuration file to be copied to
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# /etc/nixos/configuration.nix.
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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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}:
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assert partitionTableType == "legacy" || partitionTableType == "legacy+gpt" || partitionTableType == "efi" || partitionTableType == "hybrid" || partitionTableType == "none";
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# We use -E offset=X below, which is only supported by e2fsprogs
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assert partitionTableType != "none" -> fsType == "ext4";
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# Either both or none of {user,group} need to be set
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assert lib.all
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(attrs: ((attrs.user or null) == null)
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== ((attrs.group or null) == null))
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contents;
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with lib;
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let format' = format; in let
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format = if format' == "qcow2-compressed" then "qcow2" else format';
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compress = optionalString (format' == "qcow2-compressed") "-c";
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filename = "nixos." + {
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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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}.${format} or format;
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rootPartition = { # switch-case
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legacy = "1";
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"legacy+gpt" = "2";
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efi = "2";
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hybrid = "3";
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}.${partitionTableType};
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partitionDiskScript = { # switch-case
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legacy = ''
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parted --script $diskImage -- \
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mklabel msdos \
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mkpart primary ext4 1MiB -1
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'';
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"legacy+gpt" = ''
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parted --script $diskImage -- \
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mklabel gpt \
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mkpart no-fs 1MB 2MB \
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set 1 bios_grub on \
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align-check optimal 1 \
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mkpart primary ext4 2MB -1 \
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align-check optimal 2 \
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print
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'';
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efi = ''
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parted --script $diskImage -- \
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mklabel gpt \
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mkpart ESP fat32 8MiB ${bootSize} \
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set 1 boot on \
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mkpart primary ext4 ${bootSize} -1
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'';
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hybrid = ''
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parted --script $diskImage -- \
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mklabel gpt \
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mkpart ESP fat32 8MiB ${bootSize} \
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set 1 boot on \
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mkpart no-fs 0 1024KiB \
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set 2 bios_grub on \
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mkpart primary ext4 ${bootSize} -1
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'';
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none = "";
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}.${partitionTableType};
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nixpkgs = cleanSource pkgs.path;
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# FIXME: merge with channel.nix / make-channel.nix.
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channelSources = 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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binPath = with pkgs; makeBinPath (
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[ rsync
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util-linux
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parted
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e2fsprogs
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lkl
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config.system.build.nixos-install
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config.system.build.nixos-enter
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nix
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] ++ stdenv.initialPath);
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# I'm preserving the line below because I'm going to search for it across nixpkgs to consolidate
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# image building logic. The comment right below this now appears in 4 different places in nixpkgs :)
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# !!! should use XML.
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sources = map (x: x.source) contents;
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targets = map (x: x.target) contents;
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modes = map (x: x.mode or "''") contents;
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users = map (x: x.user or "''") contents;
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groups = map (x: x.group or "''") contents;
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closureInfo = pkgs.closureInfo { rootPaths = [ config.system.build.toplevel channelSources ]; };
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blockSize = toString (4 * 1024); # ext4fs block size (not block device sector size)
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prepareImage = ''
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export PATH=${binPath}
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# Yes, mkfs.ext4 takes different units in different contexts. Fun.
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sectorsToKilobytes() {
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echo $(( ( "$1" * 512 ) / 1024 ))
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}
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sectorsToBytes() {
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echo $(( "$1" * 512 ))
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}
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# Given lines of numbers, adds them together
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sum_lines() {
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local acc=0
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while read -r number; do
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acc=$((acc+number))
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done
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echo "$acc"
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}
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mebibyte=$(( 1024 * 1024 ))
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# Approximative percentage of reserved space in an ext4 fs over 512MiB.
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# 0.05208587646484375
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# × 1000, integer part: 52
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compute_fudge() {
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echo $(( $1 * 52 / 1000 ))
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}
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mkdir $out
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root="$PWD/root"
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mkdir -p $root
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# Copy arbitrary other files into the image
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# Semi-shamelessly copied from make-etc.sh. I (@copumpkin) shall factor this stuff out as part of
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# https://github.com/NixOS/nixpkgs/issues/23052.
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set -f
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sources_=(${concatStringsSep " " sources})
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targets_=(${concatStringsSep " " targets})
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modes_=(${concatStringsSep " " modes})
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set +f
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for ((i = 0; i < ''${#targets_[@]}; i++)); do
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source="''${sources_[$i]}"
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target="''${targets_[$i]}"
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mode="''${modes_[$i]}"
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if [ -n "$mode" ]; then
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rsync_chmod_flags="--chmod=$mode"
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else
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rsync_chmod_flags=""
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fi
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# Unfortunately cptofs only supports modes, not ownership, so we can't use
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# rsync's --chown option. Instead, we change the ownerships in the
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# VM script with chown.
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rsync_flags="-a --no-o --no-g $rsync_chmod_flags"
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if [[ "$source" =~ '*' ]]; then
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# If the source name contains '*', perform globbing.
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mkdir -p $root/$target
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for fn in $source; do
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rsync $rsync_flags "$fn" $root/$target/
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done
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else
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mkdir -p $root/$(dirname $target)
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if ! [ -e $root/$target ]; then
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rsync $rsync_flags $source $root/$target
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else
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echo "duplicate entry $target -> $source"
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exit 1
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fi
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fi
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done
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export HOME=$TMPDIR
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# Provide a Nix database so that nixos-install can copy closures.
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export NIX_STATE_DIR=$TMPDIR/state
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nix-store --load-db < ${closureInfo}/registration
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chmod 755 "$TMPDIR"
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echo "running nixos-install..."
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nixos-install --root $root --no-bootloader --no-root-passwd \
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--system ${config.system.build.toplevel} --channel ${channelSources} --substituters ""
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diskImage=nixos.raw
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${if diskSize == "auto" then ''
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${if partitionTableType == "efi" || partitionTableType == "hybrid" then ''
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# Add the GPT at the end
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gptSpace=$(( 512 * 34 * 1 ))
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# Normally we'd need to account for alignment and things, if bootSize
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# represented the actual size of the boot partition. But it instead
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# represents the offset at which it ends.
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# So we know bootSize is the reserved space in front of the partition.
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reservedSpace=$(( gptSpace + $(numfmt --from=iec '${bootSize}') ))
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'' else if partitionTableType == "legacy+gpt" then ''
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# Add the GPT at the end
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gptSpace=$(( 512 * 34 * 1 ))
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# And include the bios_grub partition; the ext4 partition starts at 2MB exactly.
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reservedSpace=$(( gptSpace + 2 * mebibyte ))
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'' else if partitionTableType == "legacy" then ''
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# Add the 1MiB aligned reserved space (includes MBR)
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reservedSpace=$(( mebibyte ))
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'' else ''
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reservedSpace=0
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''}
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additionalSpace=$(( $(numfmt --from=iec '${additionalSpace}') + reservedSpace ))
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# Compute required space in filesystem blocks
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diskUsage=$(find . ! -type d -exec 'du' '--apparent-size' '--block-size' "${blockSize}" '{}' ';' | cut -f1 | sum_lines)
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# Each inode takes space!
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numInodes=$(find . | wc -l)
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# Convert to bytes, inodes take two blocks each!
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diskUsage=$(( (diskUsage + 2 * numInodes) * ${blockSize} ))
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# Then increase the required space to account for the reserved blocks.
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fudge=$(compute_fudge $diskUsage)
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requiredFilesystemSpace=$(( diskUsage + fudge ))
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diskSize=$(( requiredFilesystemSpace + additionalSpace ))
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# Round up to the nearest mebibyte.
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# This ensures whole 512 bytes sector sizes in the disk image
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# and helps towards aligning partitions optimally.
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if (( diskSize % mebibyte )); then
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diskSize=$(( ( diskSize / mebibyte + 1) * mebibyte ))
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fi
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truncate -s "$diskSize" $diskImage
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printf "Automatic disk size...\n"
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printf " Closure space use: %d bytes\n" $diskUsage
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printf " fudge: %d bytes\n" $fudge
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printf " Filesystem size needed: %d bytes\n" $requiredFilesystemSpace
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printf " Additional space: %d bytes\n" $additionalSpace
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printf " Disk image size: %d bytes\n" $diskSize
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'' else ''
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truncate -s ${toString diskSize}M $diskImage
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''}
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${partitionDiskScript}
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${if partitionTableType != "none" then ''
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# Get start & length of the root partition in sectors to $START and $SECTORS.
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eval $(partx $diskImage -o START,SECTORS --nr ${rootPartition} --pairs)
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mkfs.${fsType} -b ${blockSize} -F -L ${label} $diskImage -E offset=$(sectorsToBytes $START) $(sectorsToKilobytes $SECTORS)K
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'' else ''
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mkfs.${fsType} -b ${blockSize} -F -L ${label} $diskImage
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''}
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echo "copying staging root to image..."
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cptofs -p ${optionalString (partitionTableType != "none") "-P ${rootPartition}"} -t ${fsType} -i $diskImage $root/* / ||
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(echo >&2 "ERROR: cptofs failed. diskSize might be too small for closure."; exit 1)
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'';
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in pkgs.vmTools.runInLinuxVM (
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pkgs.runCommand name
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{ preVM = prepareImage;
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buildInputs = with pkgs; [ util-linux e2fsprogs dosfstools ];
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postVM = ''
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${if format == "raw" then ''
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mv $diskImage $out/${filename}
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'' else ''
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${pkgs.qemu}/bin/qemu-img convert -f raw -O ${format} ${compress} $diskImage $out/${filename}
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''}
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diskImage=$out/${filename}
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${postVM}
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'';
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memSize = 1024;
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}
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''
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export PATH=${binPath}:$PATH
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rootDisk=${if partitionTableType != "none" then "/dev/vda${rootPartition}" else "/dev/vda"}
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# Some tools assume these exist
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ln -s vda /dev/xvda
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ln -s vda /dev/sda
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# make systemd-boot find ESP without udev
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mkdir /dev/block
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ln -s /dev/vda1 /dev/block/254:1
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mountPoint=/mnt
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mkdir $mountPoint
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mount $rootDisk $mountPoint
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# Create the ESP and mount it. Unlike e2fsprogs, mkfs.vfat doesn't support an
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# '-E offset=X' option, so we can't do this outside the VM.
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${optionalString (partitionTableType == "efi" || partitionTableType == "hybrid") ''
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mkdir -p /mnt/boot
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mkfs.vfat -n ESP /dev/vda1
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mount /dev/vda1 /mnt/boot
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''}
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# Install a configuration.nix
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mkdir -p /mnt/etc/nixos
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${optionalString (configFile != null) ''
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cp ${configFile} /mnt/etc/nixos/configuration.nix
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''}
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# Set up core system link, GRUB, etc.
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NIXOS_INSTALL_BOOTLOADER=1 nixos-enter --root $mountPoint -- /nix/var/nix/profiles/system/bin/switch-to-configuration boot
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# The above scripts will generate a random machine-id and we don't want to bake a single ID into all our images
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rm -f $mountPoint/etc/machine-id
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# Set the ownerships of the contents. The modes are set in preVM.
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# No globbing on targets, so no need to set -f
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targets_=(${concatStringsSep " " targets})
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users_=(${concatStringsSep " " users})
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groups_=(${concatStringsSep " " groups})
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for ((i = 0; i < ''${#targets_[@]}; i++)); do
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target="''${targets_[$i]}"
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user="''${users_[$i]}"
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group="''${groups_[$i]}"
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if [ -n "$user$group" ]; then
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# We have to nixos-enter since we need to use the user and group of the VM
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nixos-enter --root $mountPoint -- chown -R "$user:$group" "$target"
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fi
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done
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umount -R /mnt
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# Make sure resize2fs works. Note that resize2fs has stricter criteria for resizing than a normal
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# mount, so the `-c 0` and `-i 0` don't affect it. Setting it to `now` doesn't produce deterministic
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# output, of course, but we can fix that when/if we start making images deterministic.
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${optionalString (fsType == "ext4") ''
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tune2fs -T now -c 0 -i 0 $rootDisk
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''}
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''
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)
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