How to Avoid Becoming the Hero of 'My Program Deleted 800 GB': Safe Recursive Deletion in Bash and Python
A recent article on Habr explores how seemingly simple recursive deletion code can lead to catastrophic data loss, using the example of Telegram Desktop accidentally cleaning a custom folder and removing around 800 GB of projects and programs.
The author notes that many projects contain cleanup routines for caches, temporary files, or build artifacts that receive minimal review and later fail when variables are empty or unexpected symlinks appear.
Classic pitfalls with empty variables
Well-known incidents include the 2015 Steam Linux client bug where an unset STEAMROOT variable expanded rm -rf "$STEAMROOT/"* into rm -rf "/"*, and the 2011 Bumblebee installer that contained an extra space turning one path into rm -rf /usr /lib/nvidia-current/xorg/xorg.
Hardened Bash practices
The recommended Bash template begins with set -euo pipefail, followed by explicit checks such as ${CACHE_DIR:?CACHE_DIR not set}, double quotes around paths, and the -- separator. Additional safeguards include verifying the target is a real directory (not a symlink), resolving it with realpath, and rejecting paths that match forbidden roots like /, /home, or /usr.
The final deletion step uses find with -mindepth 1 and --one-file-system to avoid crossing mount points while still removing hidden files.
Safe Python implementation
In Python, the article warns that shutil.rmtree has identical risks and introduces a safe_rmtree function that rejects empty paths, symlinks, and targets outside a pre-defined allowed root. It relies on Path.resolve(strict=True) and is_relative_to rather than string prefix checks, and refuses to run on platforms where shutil.rmtree.avoids_symlink_attacks is False.
A dry-run mode and explicit exception handling for read-only files on Windows are also provided.
Practical recommendations
Additional advice includes using tempfile.TemporaryDirectory, leaving marker files in shared cache locations, moving files to a trash directory before final deletion, and always logging operations. The author stresses that deletion code should be reviewed as carefully as any security-sensitive routine because a single unchecked line can destroy all user data.
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