Frank
3b29e173c2
The merged door was /mnt/media, which read like a third volume and split the host state across two trees. It is now /var/lib/media-meta/view, so the array layer, the SSD upper layer, the kernel workdir, the reap trash and the merged tree are one directory — and the mount table gains no new /mnt entry beside the array. systemd names a mount unit after its ESCAPED path, so the repo copy keeps the readable name media-meta-view.mount while `install` writes the host file as var-lib-media\x2dmeta-view.mount; `plan` prints both and the page records them, so nobody hunts for a unit that "does not exist". install also creates the mount point itself, because systemd will not. The seam now additionally pins that the unit's Where= is exactly the path both containers bind — guard and bind cannot drift apart. The Quadlet Lifecycle phantom-path example is corrected too: it named an invented /mnt/media/*, while the real phantom is the legacy /opt/jellyfin/* that dankserver/compose.yaml still carries for a service whose roots moved to /home/dank/Containers/jellyfin.
118 lines
6.8 KiB
Markdown
118 lines
6.8 KiB
Markdown
---
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type: reference
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title: Media Metadata View
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description: "The SSD-backed overlay the two media servers read and write: shape, guards, commands, laws, rollback."
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tags: [dankserver, media-server, jellyfin, plex, storage]
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timestamp: 2026-10-30T00:00:00Z
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---
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# Media Metadata View
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`/var/lib/media-meta/view` is an OverlayFS merge of the media library: the RAID6
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array below, a directory on the NVMe above. It exists so [[Jellyfin]] can write
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Kodi-format sidecars (`movie.nfo`, `tvshow.nfo`, `episode.nfo`, artwork) that
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[[Plex]] can read. Sidecar metadata is only useful sitting next to the media
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file, and the array is read-only and slow — so the media bytes stay there and the
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*writes* land on SSD. One tree to both servers, one copy of the media.
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The mount point is not a volume and holds nothing while unmounted. It sits inside
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`/var/lib/media-meta` so that layers, kernel bookkeeping, the reap trash and the
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merged door are one directory — and so the mount table grows no new `/mnt` entry
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next to the array.
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## Shape
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| Item | Value |
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|---|---|
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| Lower layer | `/mnt/entropy` — the RAID6 array, source of truth, never written |
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| Upper layer | `/var/lib/media-meta/upper` — NVMe; every write lands here |
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| Work dir | `/var/lib/media-meta/work` — overlayfs internals, same filesystem |
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| Mount point | `/var/lib/media-meta/view` — the merged tree both servers bind |
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| Unit (repo) | `dankserver/host/systemd/media-meta-view.mount` — the source of truth |
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| Unit (host) | `var-lib-media\x2dmeta-view.mount` — systemd names a mount unit after its escaped path (`-` becomes `\x2d`); `media-view.sh install` writes the repo file under that name |
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| Installer | `scripts/media-view.sh` — `plan` / `install` / `verify` / `status` / `reap` |
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| Written by | Jellyfin only (Plex binds read-only); nothing else in the fleet touches it |
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Both consumers guard the view with
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`UnitConfigItem=ConditionPathIsMountPoint=/var/lib/media-meta/view`, and
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`scripts/deploy.sh dankserver --service jellyfin|plex` calls `media-view.sh
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install` + `verify` before it restarts either container.
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| Consumer | Bind | Mode | Why that path |
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|---|---|---|---|
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| [[Jellyfin]] | `/var/lib/media-meta/view:/data` | rw | It is the metadata writer; its sidecars become SSD bytes |
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| [[Plex]] | `/var/lib/media-meta/view:/mnt/entropy` | ro | Every path in the PMS database was recorded as `/mnt/entropy/...`; only the HOST side of the bind moved, so its database still resolves |
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Putting the sidecars inside Plex's reach is not the same as making Plex use them:
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a library parses `.nfo` only with its *Local media information* agent enabled, and
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this change touches no library setting.
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## Commands
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```bash
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scripts/media-view.sh plan # print the resolved shape, touch nothing
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sudo scripts/media-view.sh install # create dirs, install the unit, mount, enable
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scripts/media-view.sh verify # is the view really the overlay? (deploy gate)
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scripts/media-view.sh status # mount options + upper-layer size/file count
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scripts/media-view.sh reap # list ghost metadata (media moved, sidecars left)
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sudo scripts/media-view.sh reap --apply # move ghosts to the SSD trash, never delete
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```
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`--upper-base DIR` and `--lower DIR` relocate the layers for `plan` and `reap`;
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the defaults are the host values above.
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## Laws
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- **The upper layer must sit on non-rotational storage.** `install` and `verify`
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refuse via `lsblk -dno ROTA` if the upper base lives on the array: an overlay
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whose upper is the spinners is the original problem with extra steps, and it
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silently turns every metadata write back into a seek.
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- **Never mount the view over an unmounted lower.** `RequiresMountsFor=/mnt/entropy`
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plus the container `ConditionPathIsMountPoint` guards: an empty `lowerdir`
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presents an *empty library* as truth, and a media scan would then clear the
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database of everything. systemd does not create a mount point, so `install`
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creates `view` itself; without it the mount simply fails.
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- **Never delete through the view.** A delete writes an overlayfs whiteout
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(`.wh.<name>`) in the upper layer, which hides the array's copy without
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removing it — the file reappears the moment the view is unmounted, and the
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upper layer now carries a landmine. Deletions belong on the raw path
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(`/mnt/entropy`), which the relayout tool already treats as the only writer.
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`reap` refuses to remove whiteouts and only warns about them.
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- **A relayout must be followed by `reap`.** Renames happen on the raw path, so
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sidecars the view already wrote stay at the old coordinates: a ghost folder
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the servers browse and find nothing in. `reap` lists upper-layer directories
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with no counterpart below and moves them (with their subtree) into a dated
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`.AGENTTRASH/` under the SSD base. It is recursive and file-safe: a sidecar
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that exists only above is normal, so only *directories* are candidates.
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- **File-watcher events do not cross the overlay.** Plex's NFO agent and
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Jellyfin's real-time monitor see inotify events for writes that land *in the
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upper layer*, not for changes on the array underneath. After any relayout or
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externally-written metadata, trigger a library refresh — see
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[[Media Relayout]] for the refresh procedure.
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## Failure signatures
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| Symptom | Meaning |
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|---|---|
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| `jellyfin.service` / `plex.service` show `ConditionPathIsMountPoint=... was not met` and stay inactive | The view is not mounted. Do not start them anyway: `scripts/media-view.sh install`, then `verify`. |
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| Jellyfin log: `Read-only file system : '/data/Movies/…/movie.nfo'` | The container is binding the raw array, not the view — the quadlet drifted back or the view is gone. `media-view.sh status`. |
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| A folder appears in a media server with artwork/`.nfo` but no video | Ghost metadata from a relayout. `media-view.sh reap`. |
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| `verify` prints `refused: …/view is not a mountpoint` | A plain directory is sitting where the overlay belongs. That is the fail-closed guard working; `install` on the box. |
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| `systemctl status` finds no such unit | Look under the escaped name, `var-lib-media\x2dmeta-view.mount`, not the repo file name. |
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## Rollback
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Revert the commit that pointed the two quadlets at the view and re-deploy both
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services — they bind `/mnt/entropy` read-only again, which is the pre-view shape.
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The NVMe upper layer can stay: nothing reads it once the binds are back, and it
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holds no state either server needs. Unmounting alone
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(`systemctl stop 'var-lib-media\x2dmeta-view.mount'`) is safe while no container
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binds it, and the array is never modified by any of this.
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## Links
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- [[Jellyfin]] — the metadata writer; its data layout section.
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- [[Plex]] — the read-only consumer; in-place bind-mount history.
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- [[Media Relayout]] — the tool that moves media on the raw path and the reason `reap` exists.
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- [[Entropy Volume]] — the array underneath.
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