Python Preserve File Metadata When Creating Backups

Decide which file attributes matter when making backups.

How It Works

Copying content alone does not necessarily preserve modification timestamps, access permissions or ownership. shutil.copy2() attempts to preserve supported metadata, while tar archives can store additional Unix-style attributes. Preservation remains platform-dependent and should be verified during restore.

Backups are trustworthy only after integrity checks and restore verification, not merely a successful copy call.

Step-by-Step Example

from pathlib import Path
from tempfile import TemporaryDirectory
import shutil

with TemporaryDirectory() as folder:
    original = Path(folder) / "original.txt"
    backup = Path(folder) / "backup.txt"
    original.write_text("backup sample", encoding="utf-8")
    shutil.copy2(original, backup)
    print(original.read_bytes() == backup.read_bytes())
    print(abs(original.stat().st_mtime - backup.stat().st_mtime) < 1)

Understanding the Example

• The with block manages the opened resource and closes it when the block finishes, including when an exception occurs.
• The expression 'Path(folder) / "original.txt"' supplies the value stored as 'original'. This value is then used or checked by the later statements.

A successful run of this example prints the following output:

True
True

Where This Fits in a Real Program

A practical archive workflow has separate decisions for selection, compression, extraction and verification. When files come from other people, inspect paths, member counts and uncompressed sizes before writing anything; a successful decompression does not establish that its contents are trustworthy.

Practice: Try It Yourself

Use stat() to compare source and backup timestamps, then explain why a restore test is still necessary.

For this exercise, predict the result before running the changed code. Then explain the difference between the original and modified cases using the actual values, not just whether the program completed.

Further Reading

Read the official Python documentation for complete parameters, return types and exceptions.

Common Beginner Mistakes

• Assuming that copying bytes automatically preserves timestamps or file modes.
• Promise exact ownership and permission preservation across Windows, Linux and archive formats.

Key Takeaways

• Decide which file attributes matter when making backups.
• Copying content alone does not necessarily preserve modification timestamps, access permissions or ownership.
• Backups are trustworthy only after integrity checks and restore verification, not merely a successful copy call.