Instruction 04-sabnzbd-and-usenet-downloading: Reading

SABnzbd is a queue-driven Usenet download client. It does not search the public internet for media and it does not normally discover posts by itself. An operator or an authorized automation client supplies an NZB document. That XML document lists message identifiers for articles stored by a Usenet provider. SABnzbd connects to the configured provider, authenticates, requests those articles, decodes their payloads, and reconstructs the files represented by the job. A complete system therefore has distinct roles: an indexer describes where articles are located, a provider serves the articles, SABnzbd performs retrieval and post-processing, and an optional library manager imports approved completed files.

The normal processing path is intake, queueing, article retrieval, verification, optional PAR2 repair, optional archive extraction, and placement in a completed destination. Incomplete data should remain separate from completed output. This prevents downstream applications from importing partial archives or files that have not passed verification. Categories provide a controlled handoff mechanism: a category such as documents, audio, or video can map to its own completed subdirectory and processing policy. Category names and paths must agree with any automation client that submits jobs.

Provider settings affect reliability and privacy. Use the provider's documented TLS endpoint and verify certificates. Port 563 is commonly used for NNTP over TLS, but the provider's documentation remains authoritative. A large connection limit is not automatically faster or better; exceeding the provider's allowance can cause authentication failures, throttling, or unstable transfers. Start conservatively and remain within the purchased plan. A second provider or block account may improve completion when it has a genuinely independent article source, but it should have a lower priority so it is used only when the primary cannot supply an article.

Retention and completion are different. Retention is an age claim, while completion describes whether the exact referenced articles still exist. A job may be young enough for the provider's retention window yet still fail because some articles were removed, never propagated, or are unavailable on that provider. PAR2 can repair only within the amount of available recovery data; it cannot recreate unlimited missing content.

The web interface is an administrative control plane. Bind it to loopback or a trusted internal address and place authenticated, encrypted access in front of it when remote administration is required. Protect provider credentials and API keys as secrets. Do not embed them in shared configuration examples, source repositories, NZB files, or logs. Review post-processing scripts especially carefully because they execute after handling untrusted downloaded input. This class uses a synthetic NZB containing no external payload and performs no network requests. The resulting policy report demonstrates path separation, local-only administration, provider TLS intent, conservative connection use, and category mapping before a real installation is configured.