Create writable overlay layers in bubblewrap with --overlay-src / --overlay / --tmp-overlay / --ro-overlay

domain: github.com/containers/bubblewrap · 7 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗

Documented steps

  1. Declare read-only layer sources with --overlay-src SRC immediately before the consuming overlay option — it 'does nothing on its own'.
  2. Persistent read-write overlay: --overlay RWSRC WORKDIR DEST mounts overlayfs at DEST using RWSRC plus all immediately preceding --overlay-src layers.
  3. Throwaway writable overlay: --tmp-overlay DEST — writes go to the tmpfs hosting the sandbox root, accessible from neither host nor child afterward.
  4. Read-only merged view: --ro-overlay DEST — requires at least two preceding --overlay-src entries.
  5. Keep sources disjoint: no overlay source may be an ancestor of another.
  6. Check versions: these options landed in v0.11.0 (2024-10-30) — older packaged bwrap lacks them entirely.
  7. Reference (official docs): https://raw.githubusercontent.com/containers/bubblewrap/main/bwrap.xml ; https://github.com/containers/bubblewrap/releases/tag/v0.11.0

Known gotchas

Related routes

Give a bubblewrap (bwrap) sandbox a writable overlay filesystem so an untrusted process can write to what looks like a full directory tree without touching host files, using --overlay, --tmp-overlay, or --ro-overlay.
github.com/containers/bubblewrap · 5 steps · unrated
Use bwrap overlay mounts (--overlay-src, --overlay, --tmp-overlay, --ro-overlay) to give a sandbox a throwaway writable view of a read-only tree
github.com/containers/bubblewrap · 8 steps · unrated
Choose correctly between bwrap --bind, --ro-bind and --dev-bind and make only one working directory writable
github.com/containers/bubblewrap · 9 steps · unrated

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