2.4 peipkg-compose
peipkg-compose builds a filesystem tree from packages, without
installing anything onto the machine doing the building. It is how an
image is assembled.
It shares peipkg's resolver, its archive reader, its claim logic, and its package database schema. What it does not share is the runtime: it has no transaction journal to recover, no lock to hold against a running system, and no operator sitting in front of it.
Composition runs in two phases, and they can be run separately.
Resolve performs the full repository trust ceremony, resolves the requested package set against the configured repositories' indexes, and writes a lock: the pinned closure, with each package's URL and hash.
Build reads the lock, fetches each package, checks its bytes against the hash the lock recorded, and assembles the tree — extracting payload, materialising claim links, and seeding a package database so that the resulting image knows what it contains.
Chapter 10 describes composition in detail, including what it does not do that an installed system's peipkg would.