git-fsck-objects

git-fsck-objects [-v] [--unreachable] [--tags] [--full] [--strict]

-v, --verbose
    Enable verbose mode, showing progress and details during scan.

--unreachable
    Detect and report objects not reachable from any reference (potential orphans).

--tags
    Verify tags reference valid commits, trees, blobs, or other tags (not refs).

--full
    Scan all objects in repository, including loose unreachable ones (resource-intensive).

--strict
    Treat dangling objects as errors, exiting non-zero instead of warning.

git-fsck-objects is a low-level Git command for diagnosing repository health by scanning the object database (.git/objects). It checks SHA-1 checksums of every object, validates object formats, and verifies referential integrity—ensuring referenced objects exist and match expected checksums.

Starting from references (heads, tags, notes, etc.), it traverses the object graph. Missing objects cause 'broken link' errors; corrupt files trigger 'checksum mismatch' or 'invalid format' warnings.

It distinguishes dangling objects (valid but unreferenced, often harmless from ops like rebase) from unreachable ones (not traversable from refs). Options extend scanning: --full inspects all loose objects; --unreachable lists detached objects.

Ideal for detecting disk corruption, incomplete clones, or fs issues. Run periodically on servers. Non-zero exit on problems. Modern Git prefers git fsck [--full]; this is legacy but equivalent.

Slow on large repos with --full; skips packed objects unless unpacked. Detects but does not fix issues—use git prune or git gc afterward. Run as repository owner to avoid permission errors.

0: OK
1: warnings (dangling/unreachable)
128: fatal error (corruption, I/O fail).

broken: missing <oid>
dangling blob <oid>
unreachable commit <oid>
checksum mismatch <oid>.

Created by Linus Torvalds in 2005 as git-fsck-objects for early Git (pre-1.5.4). Unified into git fsck by Junio C Hamano; --full replicates original behavior. Evolved with Git for better progress reporting, connectivity checks.

git fsck(1), git gc(1), git prune(1), git reflog(1)