git verify-pack

Use after a suspicious push/clone to confirm sanity.

🎯 What & why

git verify-pack walks a packfile via its index and confirms each object's checksum and chain. Run it after a suspicious push, clone, or disk scare to prove the pack is intact.

🧠 Mental model

Reads pack-XXXX.idx, then re-checksums every object in pack-XXXX.pack, following delta chains. If anything mismatches, it errors. With -v, it prints per-object size, type, and chain depth.

🛠️ Synopsis

git verify-pack [-v|--verbose] [-s|--stat-only] <pack>.idx ...

🎚️ Switches & options

Flag	What it does
`<pack>.idx`	Required: path to the .idx file (the .pack must sit beside it).
`-v, --verbose`	Print one line per object: SHA, type, size, offset, depth, base.
`-s, --stat-only`	Print only the summary (counts, deltas, chain depth) - no per-object output.
`(no flag)`	Verify silently; exit 0 on success, non-zero on corruption.

💡 Use cases

Confirm a freshly-fetched pack is intact after a flaky network transfer.
Prove on-disk corruption when 'git fsck' complains about a specific pack.
Get a pack's object count, delta ratio, and max chain depth for repacking decisions.
Audit packs in .git/objects/pack/ on a server before snapshotting.

🧪 Examples

Silent integrity check

git verify-pack .git/objects/pack/pack-abcd1234.idx

Just the summary numbers

git verify-pack -s .git/objects/pack/pack-abcd1234.idx

Per-object dump for analysis

git verify-pack -v .git/objects/pack/pack-abcd1234.idx | head

Find the deepest delta chains

git verify-pack -v .git/objects/pack/*.idx | awk '$5 ~ /^[0-9]+$/ {print $5}' | sort -n | tail

🎓 Recommendations

Run 'git fsck --full' first; reach for verify-pack when fsck points at a specific pack.
Use -s for periodic health checks - per-object output is huge on real repos.
If verify-pack fails, 'git repack -a -d' from a known-good clone usually rebuilds cleanly.

🪤 Common pitfalls

You pass the .idx, not the .pack - easy to get backwards.
Verbose output on a multi-GB pack can produce millions of lines; pipe to a file or head.
A passing verify-pack proves the pack is internally consistent, NOT that objects match expected SHAs upstream.

🔗 Related modules

📝 Quiz

Hit each option, then Check answers. Score is recorded; Next is always open.