110 lines
6.0 KiB
Markdown
110 lines
6.0 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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`/mnt/media` is an OverlayFS merge of the media library: the RAID6 array below,
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a directory on the NVMe above. It exists so [[Jellyfin]] can write Kodi-format
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sidecars (`movie.nfo`, `tvshow.nfo`, `episode.nfo`, artwork) that [[Plex]] can
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read. Sidecar metadata is only useful sitting next to the media file, and the
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array is read-only and slow — so the bytes stay there and the *writes* land on
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SSD. One tree to both servers, one copy of the media.
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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 | `/mnt/media`, unit `mnt-media.mount` (`WantedBy=local-fs.target`) |
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| Repo source | `dankserver/host/systemd/mnt-media.mount` — host copy is generated state |
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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=/mnt/media`, and `scripts/deploy.sh
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dankserver --service jellyfin|plex` calls `media-view.sh install` + `verify`
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before it restarts either container.
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| Consumer | Bind | Mode | Why that path |
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|---|---|---|---|
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| [[Jellyfin]] | `/mnt/media:/data` | rw | It is the metadata writer; its sidecars become SSD bytes |
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| [[Plex]] | `/mnt/media:/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 /mnt/media 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; the defaults are the
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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.
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- **Never delete through `/mnt/media`.** 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 | `/mnt/media` 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: /mnt/media is not a mountpoint` | Someone made a plain directory there. That is the fail-closed guard working; remove it and install. |
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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
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shape. The NVMe upper layer can stay: nothing reads it once the binds are back,
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and it holds no state either server needs. Removing the mount alone
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(`systemctl stop mnt-media.mount`) is safe while no container binds it, and the
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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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