--- status: resolved opened: 2026-09-24 located-in: [mesh-catalog] fixed-by: mesh-catalog PR #54 — distribution, lavinmq, postgres and searxng converted to host directory binds; data copied and verified (mesh-store stopped cleanly first for a crash-consistent copy), old named volumes kept as the rollback path amended-design: --- # 115 — A named Docker volume is invisible to the operator, and one flag from gone ## What was observed On the control-node, 2026-09-24, mid-migration, checking every module in the catalogue for how it mounts its data. Five container mounts across four modules use a **named Docker volume** rather than a host directory: ``` distribution mesh-registry → mesh-registry-data:/var/lib/registry lavinmq mesh-broker → mesh-broker-data:/var/lib/lavinmq (+ mesh-broker-tls) postgres mesh-store → mesh-store-data:/var/lib/postgresql/data searxng valkey → searxng-valkey-data:/data ``` Every other module in the catalogue — more than forty of them — mounts a host directory, `/var/lib//...`, matching what `DATA-CUTOVER.md` and every rehearsed recipe tonight assumes. These four are the exception, not a second convention. `mesh-store` is the one that matters most: it holds every database migrated tonight, including a live `keycloak` restore verified minutes before this was written. ## Why it matters beyond this instance [`03-DESIGN/01-to-be/22-the-work-ahead.md`](../../03-DESIGN/01-to-be/22-the-work-ahead.md) shows this was a deliberate choice, not an oversight — *"Data survives on the named volumes"* — but that sentence answers a narrower question than the one this issue raises. It says a named volume survives **ordinary container recreation** (a rebuild, a `take`, a routine `docker rm -f` and push), which is true and which every module already gets from either a named volume or a host directory equally. What it does not address: a named volume is **one flag away from deleted**, in a way a host directory structurally cannot be. - `docker rm -f` alone does not remove a named volume — it persists, unreferenced, until something targets it by name. - `docker rm -fv`, `docker volume rm`, and `docker system prune --volumes` all do target it, and the difference from the command this migration already uses routinely (`docker rm -f` — see `HANDOFF.md`'s own "a restart does not re-read anything" rule) is one character. - A named volume is invisible to an operator working the way this migration has worked all night: `ls`, `find`, `grep` across `/services/*` and `/var/lib/*`. Finding it requires knowing to ask Docker (`docker volume inspect`), and its actual bytes sit under `/var/lib/docker/volumes//_data`, a path nothing points at. - Nothing external can back it up, snapshot it, or notice it growing without going through Docker's own volume machinery — a host directory is a directory; a filesystem-level backup job already reaches it for free. `mesh-store` carries the sharpest version of this: every module's database, the mesh's own inventory, identity and licence stores — the single foundation piece the rest of the mesh depends on — sits somewhere the operator's ordinary tools do not look. ## Decided **Persistent data is a host directory bind, never a named volume. A named volume may hold only data that is disposable if lost.** All four hold real state and all four are in scope — including `mesh-registry` and `searxng`'s cache, not only `mesh-store`. Decided 2026-09-24; the record is [ADR 0107](../../02-DECISIONS/0107-persistent-data-is-a-directory-bind-never-a-named-volume.md). ## Open questions - The safe migration path for each, in order of stakes — `mesh-store` live and holding every database migrated tonight, `mesh-broker`, `mesh-registry`, then `searxng`'s cache, which is genuinely disposable and may not need migrating at all if it is rebuilt rather than moved. - Should the catalogue refuse a module declaring a named volume for anything but disposable data at `module add`, the way [issue 091](../091-a-module-definition-carries-a-machine-port/00-report.md) asks the same of a hardcoded machine port — so a convention violation is caught at registration rather than found by reading the whole catalogue?