On the device, package BLOBs are stored in a content-addressable filesystem optimized for write-once, read-often files called blobfs. This allows them to be de-duplicated across all packages and cryptographically verified using their hash. Fuchsia runs the pkg-cache service on top of blobfs to facilitate package management.
![Diagram illustrating how the package cache is built on top of “blobfs” — a content-addressable filesystem that de-duplicates BLOBs allowing them to be shared between packages.] (/docs/get-started/images/intro/blobfs.png){: width=“632”}
The pkg-cache layer tracks which packages in the system are currently active. Packages are not explicitly installed or removed in Fuchsia. Software is delivered on demand and likewise space can be reclaimed from packages that are no longer active through periodic garbage collection. When pkg-cache triggers garbage collection to reclaim space, content BLOBs not referenced by any active package are deleted.
Note: For more of the technical details on Fuchsia packages and software delivery, see the package documentation.
