dotnet/efcore · error · FileNotFoundError

Could not find 'data.tar.*' in

Error message

Could not find 'data.tar.*' in {deb_file}.

What it means

Raised by extract_deb_file (a FileNotFoundError) when 'ar t' lists the archive members and none of them starts with 'data.tar'. It means the file on disk is not a valid .deb, or its data payload is absent or named differently.

Solutions

1. Inspect the file: run `file <deb_file>` and `head -c 200 <deb_file>` to see whether it is HTML instead of an ar archive.
2. Run `ar t <deb_file>` manually to see the actual member list.
3. Verify --mirror/--suite/--arch produce the right download URLs.
4. Re-run in case it was a transient mirror/CDN issue serving the wrong body.

Example fix

// before
result = subprocess.run([ar_tool, "t", os.path.abspath(deb_file)], cwd=tmp_subdir, check=True, ...)

// after
with open(deb_file, "rb") as fh:
    if fh.read(8) != b"!<arch>\n":
        raise FileNotFoundError(f"{deb_file} is not a valid .deb (bad magic bytes)")
result = subprocess.run([ar_tool, "t", os.path.abspath(deb_file)], cwd=tmp_subdir, check=True, ...)

# preflight: verify each downloaded file is a real .deb (ar magic) before extracting
import os
def is_deb(p):
    with open(p, "rb") as fh:
        return fh.read(8) == b"!<arch>\n"
bad = [f for f in os.listdir(tmp_dir) if f.endswith(".deb") and not is_deb(os.path.join(tmp_dir, f))]
if bad:
    sys.exit(f"downloaded files are not valid .deb (likely HTML error pages): {bad}")

When it happens

Trigger: The file at {tmp_dir}/{basename(filename)} is passed to ar t, and no output line begins with 'data.tar'. Typically because the file is not a .deb at all.

Common situations: The mirror served an HTML error page (custom 404 page returned with status 200), a partial/truncated download, a proxy injecting an HTML block page, a wrong suite so a different file was downloaded, or a corrupted deb.

Related errors

• Failed to download , Status Code
• SHA256 mismatch for : expected , got
• Unsupported compression format
• Could not find checksum for
• Failed to download after attempts.

AI-assisted analysis of dotnet/efcore@3a2006ef56 (2026-08-11). Data as JSON: /api/errors/c1bd751120a71d67. Report an issue: GitHub.

Appendix: source

Thrown at eng/common/cross/install-debs.py:308

    print("All done!")

def extract_deb_file(deb_file, tmp_dir, extract_dir, ar_tool):
    """Extract .deb file contents"""

    os.makedirs(extract_dir, exist_ok=True)

    with tempfile.TemporaryDirectory(dir=tmp_dir) as tmp_subdir:
        result = subprocess.run([ar_tool, "t", os.path.abspath(deb_file)], cwd=tmp_subdir, check=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)

        tar_filename = None
        for line in result.stdout.decode().splitlines():
            if line.startswith("data.tar"):
                tar_filename = line.strip()
                break

        if not tar_filename:
            raise FileNotFoundError(f"Could not find 'data.tar.*' in {deb_file}.")

        tar_file_path = os.path.join(tmp_subdir, tar_filename)
        print(f"Extracting {tar_filename} from {deb_file}..")

        with open(tar_file_path, "wb") as outfile:
            subprocess.run([ar_tool, "p", os.path.abspath(deb_file), tar_filename], check=True, stdout=outfile, stderr=subprocess.PIPE)

        file_extension = os.path.splitext(tar_file_path)[1].lower()

        if file_extension == ".xz":
            mode = "r:xz"
        elif file_extension == ".gz":
            mode = "r:gz"
        elif file_extension == ".zst":
            # zstd is not supported by standard library yet
            decompressed_tar_path = tar_file_path.replace(".zst", "")
            with open(tar_file_path, "rb") as zst_file, open(decompressed_tar_path, "wb") as decompressed_file:
                dctx = zstandard.ZstdDecompressor()

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