git pack-objects: Usage, Options & Common CI Errors

git pack-objects compresses a set of Git objects into an efficient packfile.

Packing is what makes fetch, push, and storage efficient. You rarely call pack-objects directly, but understanding it explains repack behavior and the memory errors big repos hit in CI.

What it does

git pack-objects takes a list of object ids and writes a single delta-compressed packfile (plus an index), reusing existing deltas where possible to minimize size.

Common usage

Terminal

git pack-objects --revs --stdout < object-list > out.pack
git rev-list --objects --all | git pack-objects pack-prefix
git pack-objects --all --stdout > everything.pack

Options

Flag	What it does
--stdout	Write the pack to standard output
--revs	Read commits and pack reachable objects
--all	Pack objects from all refs
--window=<n> / --depth=<n>	Tune delta search
--threads=<n>	Parallel delta compression

Common errors in CI

fatal: Out of memory, malloc failed during delta compression on large repos - lower pack.windowMemory / pack.deltaCacheSize, or reduce --window and --threads on memory-limited runners. "fatal: packfile is corrupted" points at a truncated artifact or a disk that filled mid-write.

Related guides

git repack: Usage, Options & Common CI Errorsgit repack combines loose objects and packs into fewer, tighter packfiles. Reference for -a, -d, -A, and the… git rev-list: Usage, Options & Common CI Errorsgit rev-list lists commit objects in reverse order, the plumbing behind counting and walking history. Referen… git count-objects: Usage, Options & Common CI Errorsgit count-objects reports how many loose objects and packs a repo holds and their disk size. Reference for -v… git prune: Usage, Options & Common CI Errorsgit prune deletes unreachable objects from the object store. Reference for -n, --expire, and why gc is usuall…