Nix/Q/What does nix config show download-buffer-size of 67108864 mean in practice?
What does nix config show download-buffer-size reporting 67108864 mean in practice?
Answer
- AI/Response
- The number is bytes:
67108864 = 64 MiB (64 × 2^20). That matches the current default for the Nix setting download-buffer-size documented in the Nix reference manual. - Practical meaning: Nix keeps an in-memory buffer between the
curl side of a download and whatever consumes the bytes next (for example unpacking a tarball or writing store objects). The setting is the maximum size of that buffer—not a disk quota, not a “download cap,” and not the size of the thing you are fetching. - When it matters: If the network delivers data faster than the consumer processes it, the buffer fills. Nix then backpressures the download (you may see warnings like “download buffer is full”). A larger buffer gives more slack so fast downloads can stay ahead of slow consumers; a smaller one tends to produce that warning more often on very fast links or large paths, even though work usually continues.
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