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#!/usr/bin/env python3
"""Build a composefs dump from a Json config
See the man page of composefs-dump for details about the format:
https://github.com/containers/composefs/blob/main/man/composefs-dump.md
Ensure to check the file with the check script when you make changes to it:
./check-build-composefs-dump.sh ./build-composefs_dump.py
"""
import glob
import json
import os
import sys
from enum import Enum
from pathlib import Path
from typing import Any
Attrs = dict[str, Any]
class FileType(Enum):
"""The filetype as defined by the `st_mode` stat field in octal
You can check the st_mode stat field of a path in Python with
`oct(os.stat("/path/").st_mode)`
"""
directory = "4"
file = "10"
symlink = "12"
class ComposefsPath:
path: str
size: int
filetype: FileType
mode: str
uid: str
gid: str
payload: str
rdev: str = "0"
nlink: int = 1
mtime: str = "1.0"
content: str = "-"
digest: str = "-"
def __init__(
self,
attrs: Attrs,
size: int,
filetype: FileType,
mode: str,
payload: str,
path: str | None = None,
):
if path is None:
path = attrs["target"]
self.path = path
self.size = size
self.filetype = filetype
self.mode = mode
self.uid = attrs["uid"]
self.gid = attrs["gid"]
self.payload = payload
def write_line(self) -> str:
line_list = [
str(self.path),
str(self.size),
f"{self.filetype.value}{self.mode}",
str(self.nlink),
str(self.uid),
str(self.gid),
str(self.rdev),
str(self.mtime),
str(self.payload),
str(self.content),
str(self.digest),
]
return " ".join(line_list)
def eprint(*args: Any, **kwargs: Any) -> None:
print(*args, **kwargs, file=sys.stderr)
def normalize_path(path: str) -> str:
return str("/" + os.path.normpath(path).lstrip("/"))
def leading_directories(path: str) -> list[str]:
"""Return the leading directories of path
Given the path "alsa/conf.d/50-pipewire.conf", for example, this function
returns `[ "alsa", "alsa/conf.d" ]`.
"""
parents = list(Path(path).parents)
parents.reverse()
# remove the implicit `.` from the start of a relative path or `/` from an
# absolute path
del parents[0]
return [str(i) for i in parents]
def add_leading_directories(
target: str, attrs: Attrs, paths: dict[str, ComposefsPath]
) -> None:
"""Add the leading directories of a target path to the composefs paths
mkcomposefs expects that all leading directories are explicitly listed in
the dump file. Given the path "alsa/conf.d/50-pipewire.conf", for example,
this function adds "alsa" and "alsa/conf.d" to the composefs paths.
"""
path_components = leading_directories(target)
for component in path_components:
composefs_path = ComposefsPath(
attrs,
path=component,
size=4096,
filetype=FileType.directory,
mode="0755",
payload="-",
)
paths[component] = composefs_path
def main() -> None:
"""Build a composefs dump from a Json config
This config describes the files that the final composefs image is supposed
to contain.
"""
config_file = sys.argv[1]
if not config_file:
eprint("No config file was supplied.")
sys.exit(1)
with open(config_file, "rb") as f:
config = json.load(f)
if not config:
eprint("Config is empty.")
sys.exit(1)
eprint("Building composefs dump...")
paths: dict[str, ComposefsPath] = {}
for attrs in config:
# Normalize the target path to work around issues in how targets are
# declared in `environment.etc`.
attrs["target"] = normalize_path(attrs["target"])
target = attrs["target"]
source = attrs["source"]
mode = attrs["mode"]
if "*" in source: # Path with globbing
glob_sources = glob.glob(source)
for glob_source in glob_sources:
basename = os.path.basename(glob_source)
glob_target = f"{target}/{basename}"
composefs_path = ComposefsPath(
attrs,
path=glob_target,
size=100,
filetype=FileType.symlink,
mode="0777",
payload=glob_source,
)
paths[glob_target] = composefs_path
add_leading_directories(glob_target, attrs, paths)
else: # Without globbing
if mode == "symlink" or mode == "direct-symlink":
composefs_path = ComposefsPath(
attrs,
# A high approximation of the size of a symlink
size=100,
filetype=FileType.symlink,
mode="0777",
payload=source,
)
elif os.path.isdir(source):
composefs_path = ComposefsPath(
attrs,
size=4096,
filetype=FileType.directory,
mode=mode,
payload=source,
)
else:
composefs_path = ComposefsPath(
attrs,
size=os.stat(source).st_size,
filetype=FileType.file,
mode=mode,
# payload needs to be relative path in this case
payload=target.lstrip("/"),
)
paths[target] = composefs_path
add_leading_directories(target, attrs, paths)
composefs_dump = ["/ 4096 40755 1 0 0 0 0.0 - - -"] # Root directory
for key in sorted(paths):
composefs_path = paths[key]
eprint(composefs_path.path)
composefs_dump.append(composefs_path.write_line())
print("\n".join(composefs_dump))
if __name__ == "__main__":
main()
|
