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Storage and COW

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Danil Vilmont edited this page Aug 4, 2026 · 3 revisions

Storage and COW

Blueprint volumes use cow, ro, or rw intent:

  • cow creates an isolated writable instance view from clean source content.
  • ro protects the source through a private writable instance view; it is not a strict read-only bind mount.
  • rw intentionally links persistent single-writer instance state to a shared source and receives no rollback or backup from SLS-LITE.

With storage.strategy: auto, SLS-LITE prefers:

  1. Reflink
  2. Eligible Btrfs snapshot
  3. Kernel OverlayFS
  4. Rootless fuse-overlayfs
  5. Portable copy

Each native choice requires a successful probe on the actual configured path. An operator snapshot helper is explicit-only and never auto-discovered. Missing privileges, /dev/fuse, filesystem support, or helper access do not justify weakening a hosting provider's normal security profile; auto uses portable copy instead.

Always budget enough disk for portable fallback and keep source worlds unchanged while preparation is running.

Canonical reference: Blueprint Volumes. Operational probes and recovery are documented in Operations.

Canonical documentation: repository docs | license

SLS-LITE

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