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Pack Types

Pack Types

Every pack subcommand is a registered type. A type decides the default compression, how files are laid out into layers, which annotations and metadata files the slice carries, and which checks run at compose time. List them with sandwichcake types.

Common flags for all types are documented under pack. The sections below only list type-specific options and defaults.

TypeDefault compressionSplitting
venvzstdon
weightnoneon
binarygzipon
patchgzipon
othergzipon

venv

Packs a Python virtualenv.

FlagDefaultDescription
--pythonembeddedembedded = the venv carries its own interpreter; system = it expects the base image’s
--lock–Path to a lock file (uv.lock, poetry.lock, requirements.txt) attached as slice metadata
--from-lock–Build the venv from a lock file using local uv; requires --python <version>

At pack time the venv is scanned for ELF binaries; the maximum glibc>=X.Y requirement (or musl) is recorded in the slice annotations and checked against the base image at compose time (see libc resolution).

--from-lock resolves and installs the environment locally with uv, then packs the result — no manual venv needed:

sandwichcake pack venv --root /opt/venv \
  --from-lock uv.lock --python 3.12 \
  --to registry.example.com/ai/venv:torch-2.8

weight

Packs model weights. Implements the Namer interface: with --to-prefix instead of --to, the target ref is derived automatically from --source (e.g. hf://org/name@rev).

FlagDefaultDescription
--source–Provenance URI (hf://org/name@rev, https://…, s3://…) recorded in annotations and used for auto-naming

Weight layers default to no compression: quantized tensors do not compress, so skipping gzip saves the pack time entirely (--compression still overrides).

binary

Packs a directory of compiled binaries/libraries. The embedded ELF scanner extracts architecture, interpreter and the maximum glibc>=X.Y requirement at pack time; mixed architectures in one directory are rejected. compose reports an error when a glibc requirement meets a musl base, and a warning when the base libc cannot be verified (see libc resolution).

patch

Packs a file-level patch to overlay onto a base image.

FlagDefaultDescription
--base–Expected base repo@digest this patch applies to

other

Generic type with no extra semantics — use it for directory trees that don’t fit the specialized types.

Writing your own type

Types implement the Type interface in pkg/types (options, defaults, layout rules, annotations, metadata files, compose-time checks) and register via types.Register. The built-ins under pkg/types/ are the reference implementations.

Slicescake.yaml Reference