nixpkgs/nixos/modules/image/repart-image.nix

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# This is an expression meant to be called from `./repart.nix`, it is NOT a
# NixOS module that can be imported.
{ lib
, runCommand
, python3
, black
, ruff
, mypy
, systemd
, fakeroot
, util-linux
# filesystem tools
, dosfstools
, mtools
, e2fsprogs
, squashfsTools
, erofs-utils
, btrfs-progs
, xfsprogs
# compression tools
, zstd
, xz
# arguments
, imageFileBasename
, compression
, fileSystems
, partitions
, split
, seed
, definitionsDirectory
, sectorSize
}:
let
amendRepartDefinitions = runCommand "amend-repart-definitions.py"
{
# TODO: ruff does not splice properly in nativeBuildInputs
depsBuildBuild = [ ruff ];
nativeBuildInputs = [ python3 black mypy ];
} ''
install ${./amend-repart-definitions.py} $out
patchShebangs --build $out
black --check --diff $out
ruff --line-length 88 $out
mypy --strict $out
'';
fileSystemToolMapping = {
"vfat" = [ dosfstools mtools ];
"ext4" = [ e2fsprogs.bin ];
"squashfs" = [ squashfsTools ];
"erofs" = [ erofs-utils ];
"btrfs" = [ btrfs-progs ];
"xfs" = [ xfsprogs ];
};
fileSystemTools = builtins.concatMap (f: fileSystemToolMapping."${f}") fileSystems;
compressionPkg = {
"zstd" = zstd;
"xz" = xz;
}."${compression.algorithm}";
compressionCommand = {
"zstd" = "zstd --no-progress --threads=0 -${toString compression.level}";
"xz" = "xz --keep --verbose --threads=0 -${toString compression.level}";
}."${compression.algorithm}";
in
runCommand imageFileBasename
{
nativeBuildInputs = [
systemd
fakeroot
util-linux
compressionPkg
] ++ fileSystemTools;
} ''
amendedRepartDefinitions=$(${amendRepartDefinitions} ${partitions} ${definitionsDirectory})
mkdir -p $out
cd $out
echo "Building image with systemd-repart..."
unshare --map-root-user fakeroot systemd-repart \
--dry-run=no \
--empty=create \
--size=auto \
--seed="${seed}" \
--definitions="$amendedRepartDefinitions" \
--split="${lib.boolToString split}" \
--json=pretty \
${lib.optionalString (sectorSize != null) "--sector-size=${toString sectorSize}"} \
${imageFileBasename}.raw \
| tee repart-output.json
# Compression is implemented in the same derivation as opposed to in a
# separate derivation to allow users to save disk space. Disk images are
# already very space intensive so we want to allow users to mitigate this.
if ${lib.boolToString compression.enable}; then
for f in ${imageFileBasename}*; do
echo "Compressing $f with ${compression.algorithm}..."
# Keep the original file when compressing and only delete it afterwards
${compressionCommand} $f && rm $f
done
fi
''