borgbackup/borg

whiteout file type?

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#7174 opened on Nov 28, 2022

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help wantedos: bsdos: macOSquestion

Description

Accidentally stumbled over a file type borg does not support yet: a whiteout (used by overlay fs)

Infos:

Linux: has a hack avoiding a new file type, using a char dev 0:0 for file whiteouts and an xattr for directory whiteouts macOS: has whiteouts FreeBSD: has support for whiteouts, separate file type DT_WHT OpenBSD: no whiteouts NetBSD: ?

Is there a need for backing up / restoring whiteouts?

  • for a mounted overlay fs, it should be backed up as visible to the user (no whiteouts visible)
  • can one access the layers individually, so that WHT files would become visible (on BSD)?

Contributor guide

Tech stack
python
Domain
cli
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Understanding of overlay filesystemsKnowledge of borg's archive formatFamiliarity with Python file type handling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Investigate whether whiteout files need to be preserved in backups and how borg currently handles unknown file types. Review the kernel documentation on overlayfs whiteouts and the Python stat module. Determine the proper way to detect and store whiteout inodes on macOS, FreeBSD, and Linux. Examine borg's codebase for where file types are enumerated and archived.