A content-addressed, deduplicated backup tool targeting cheap cloud blob storage. The design follows the approach pioneered by Brad Fitzpatrick’s Brackup: large files are split into chunks using content-aware boundaries, each chunk is stored exactly once in a remote store indexed by its hash, and each backup is recorded as a manifest referencing those chunks. This makes every backup self-contained and independent while deduplication handles the incremental savings automatically.
The practical goal is to make encrypted incremental backups to AWS S3 Glacier and similar services viable, with the added option of pooling deduplicated chunks across multiple machines or users in a single store, rather than paying for a separate backup for each.
Kumiko has been rewritten several times over about fifteen years, in Java, D, and twice in Go. The current Go implementation is the most complete, and uses a Protocol Buffers-based file storage format.
Similar tools in this space include Brackup, Restic, and Duplicity. Restic maintains a comprehensive list of alternatives.