113 lines
3.3 KiB
Python
113 lines
3.3 KiB
Python
#!/usr/bin/env python
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"""Amend systemd-repart definiton files.
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In order to avoid Import-From-Derivation (IFD) when building images with
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systemd-repart, the definition files created by Nix need to be amended with the
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store paths from the closure.
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This is achieved by adding CopyFiles= instructions to the definition files.
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The arbitrary files configured via `contents` are also added to the definition
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files using the same mechanism.
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"""
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import json
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import sys
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import shutil
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from pathlib import Path
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def add_contents_to_definition(
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definition: Path, contents: dict[str, dict[str, str]] | None
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) -> None:
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"""Add CopyFiles= instructions to a definition for all files in contents."""
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if not contents:
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return
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copy_files_lines: list[str] = []
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for target, options in contents.items():
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source = options["source"]
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copy_files_lines.append(f"CopyFiles={source}:{target}\n")
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with open(definition, "a") as f:
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f.writelines(copy_files_lines)
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def add_closure_to_definition(
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definition: Path, closure: Path | None, strip_nix_store_prefix: bool | None
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) -> None:
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"""Add CopyFiles= instructions to a definition for all paths in the closure.
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If strip_nix_store_prefix is True, `/nix/store` is stripped from the target path.
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"""
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if not closure:
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return
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copy_files_lines: list[str] = []
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with open(closure, "r") as f:
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for line in f:
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if not isinstance(line, str):
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continue
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source = Path(line.strip())
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target = str(source.relative_to("/nix/store/"))
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target = f":/{target}" if strip_nix_store_prefix else ""
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copy_files_lines.append(f"CopyFiles={source}{target}\n")
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with open(definition, "a") as f:
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f.writelines(copy_files_lines)
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def main() -> None:
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"""Amend the provided repart definitions by adding CopyFiles= instructions.
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For each file specified in the `contents` field of a partition in the
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partiton config file, a `CopyFiles=` instruction is added to the
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corresponding definition file.
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The same is done for every store path of the `closure` field.
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Print the path to a directory that contains the amended repart
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definitions to stdout.
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"""
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partition_config_file = sys.argv[1]
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if not partition_config_file:
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print("No partition config file was supplied.")
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sys.exit(1)
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repart_definitions = sys.argv[2]
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if not repart_definitions:
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print("No repart definitions were supplied.")
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sys.exit(1)
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with open(partition_config_file, "rb") as f:
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partition_config = json.load(f)
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if not partition_config:
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print("Partition config is empty.")
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sys.exit(1)
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target_dir = Path("amended-repart.d")
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target_dir.mkdir()
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shutil.copytree(repart_definitions, target_dir, dirs_exist_ok=True)
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for name, config in partition_config.items():
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definition = target_dir.joinpath(f"{name}.conf")
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definition.chmod(0o644)
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contents = config.get("contents")
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add_contents_to_definition(definition, contents)
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closure = config.get("closure")
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strip_nix_store_prefix = config.get("stripNixStorePrefix")
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add_closure_to_definition(definition, closure, strip_nix_store_prefix)
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print(target_dir.absolute())
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if __name__ == "__main__":
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main()
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