fix(fleet): refuse a container start until the mount it binds has answered #109
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@@ -156,6 +156,15 @@ Unit requirements:
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(`<host>/<svc>/quadlet/`), is installed by the deployer, and is covered by
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the quadlet test seam. The host-side unit is generated state; the repo file
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is the source of truth.
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- **Bind-source gate** — a unit whose `Volume=` source is a mount this host owns
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(the entropy array, the metadata view) carries
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`ExecStartPre=/home/dank/serverAppConfigs/scripts/wait-for-mount.sh <source>`.
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Measured 2026-10-31: in a **rootless** unit `RequiresMountsFor=` is inert (the
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user manager cannot order against the system's mount unit), and
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`ConditionPathIsMountPoint=` is fail-*dead* — an unmet condition logs `skipped,
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unmet condition check` with `NRestarts=0` and no start attempt ever follows.
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Bind the array before it is mounted and the container sees the empty pre-mount
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directory as truth; a media scan then deletes the library it cannot see.
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Before declaring a service deployed: `systemctl --user is-enabled <name>` →
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`enabled`, `is-active` → `active`, and the container answers its health check.
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@@ -36,6 +36,9 @@ Volume=/home/dank/Containers/copyparty/cfg:/cfg
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PublishPort=3923:3923
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[Service]
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# /w is the array: serving the pre-mount directory instead of the volume shows an
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# empty share and nothing complains, so the mount has to answer first.
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ExecStartPre=/home/dank/serverAppConfigs/scripts/wait-for-mount.sh /mnt/entropy
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EnvironmentFile=/home/dank/Containers/copyparty/env
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Restart=always
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RestartSec=5
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@@ -43,11 +43,10 @@ PublishPort=1900:1900/udp
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Volume=/home/dank/Containers/jellyfin/config:/config
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Volume=/home/dank/Containers/jellyfin/cache:/cache
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# The view, writable: Jellyfin is the metadata writer (movie.nfo / tvshow.nfo /
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# episode.nfo + artwork) and those bytes belong on the SSD. The condition is the
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# fail-closed guard — starting against a plain, unmounted view directory would let
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# a scan conclude the library is empty.
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# episode.nfo + artwork) and those bytes belong on the SSD. The gate in [Service]
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# is the guard: started against a plain, unmounted view directory a scan decides
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# the library is empty and deletes what it cannot see.
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Volume=/var/lib/media-meta/view:/data
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UnitConfigItem=ConditionPathIsMountPoint=/var/lib/media-meta/view
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AddDevice=/dev/dri
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GroupAdd=keep-groups
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HealthCmd=curl -f http://localhost:8096/health
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@@ -56,6 +55,9 @@ HealthTimeout=10s
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HealthRetries=3
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[Service]
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# Refuse to start until the bind source is a real mount — see the header of
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# scripts/wait-for-mount.sh for the blind-boot incident this prevents.
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ExecStartPre=/home/dank/serverAppConfigs/scripts/wait-for-mount.sh /var/lib/media-meta/view /mnt/entropy
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Restart=always
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RestartSec=5
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@@ -16,10 +16,13 @@ Volume=/var/lib/plexmediaserver:/config
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# to the overlay view re-points Plex at the sidecars without touching its DB.
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# Read-only: Plex consumes the NFO files Jellyfin writes and writes no metadata.
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Volume=/var/lib/media-meta/view:/mnt/entropy:ro
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UnitConfigItem=ConditionPathIsMountPoint=/var/lib/media-meta/view
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PublishPort=32400:32400
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[Service]
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# Refuse to start until the bind source is a real mount: Plex blind is how paths
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# get marked missing in its own database. Both the view and the array under it
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# must answer — scripts/wait-for-mount.sh names the 2026-10-31 incident.
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ExecStartPre=/home/dank/serverAppConfigs/scripts/wait-for-mount.sh /var/lib/media-meta/view /mnt/entropy
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Restart=always
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RestartSec=5
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Executable
+74
@@ -0,0 +1,74 @@
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#!/usr/bin/env bash
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# wait-for-mount.sh — refuse a container start until what it binds is mounted.
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#
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# Why this exists (live 2026-10-31, Dankserver): a rootless quadlet cannot order
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# itself against a SYSTEM mount unit. `RequiresMountsFor=/mnt/entropy` in a user
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# unit resolves to nothing and is inert, so when the array's mount finished a
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# second after podman resolved the bind, Jellyfin and Plex started against the
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# pre-mount directory. Their library root looked EMPTY and Jellyfin began
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# deleting metadata by the thousand (`Removing item, Type: "Season"`). A blind
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# bind is not a cosmetic fault; it is a metadata-deleting machine.
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#
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# A `ConditionPathIsMountPoint=` is NOT the fix, measured on the same host: an
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# unmet condition logs "skipped, unmet condition check", NRestarts=0, and no
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# start attempt ever follows — the unit stays dead until a human starts it.
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# That is fail-dead. This script WAITS (the mount usually lands within seconds)
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# and only then refuses, so `Restart=always` carries the unit across the race.
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#
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# usage: wait-for-mount.sh [-t SECONDS] MOUNTPOINT [MOUNTPOINT...]
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# exit 0 every path is a mountpoint
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# exit 1 a path is still not a mountpoint after the window (named on stderr)
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# exit 2 usage error
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set -euo pipefail
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usage() { printf 'usage: %s [-t SECONDS] MOUNTPOINT [MOUNTPOINT...]\n' "$0"; }
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window=90
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while getopts ":t:h" opt; do
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case "$opt" in
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t) window=$OPTARG ;;
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h) usage; exit 0 ;;
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*) usage >&2; exit 2 ;;
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esac
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done
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shift $((OPTIND - 1))
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[ "$#" -ge 1 ] || { usage >&2; exit 2; }
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case "$window" in
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'' | *[!0-9]*) printf 'refused: -t wants whole seconds, got %s\n' "$window" >&2; exit 2 ;;
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esac
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is_mount() { findmnt -M "$1" -rno TARGET >/dev/null 2>&1; }
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report() {
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local why=$1; shift
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printf '%s:' "$why"
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for p in "$@"; do printf ' %s' "$p"; done
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printf '\n'
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}
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deadline=$(( $(date +%s) + window ))
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warned=0
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while :; do
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missing=()
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for path in "$@"; do
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is_mount "$path" || missing+=("$path")
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done
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[ "${#missing[@]}" -eq 0 ] && break
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if [ "$(date +%s)" -ge "$deadline" ]; then
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report "refused: still not mounted after ${window}s" "${missing[@]}" >&2
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printf 'refusing to start: a container bind-mounted here would see the empty\n' >&2
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printf 'directory underneath and conclude the library is empty — which is how a\n' >&2
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printf 'scan begins deleting metadata it cannot find.\n' >&2
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exit 1
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fi
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if [ "$warned" -eq 0 ]; then
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report "waiting for mount(s) this unit depends on" "${missing[@]}"
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warned=1
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fi
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sleep 1
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done
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[ "$warned" -eq 0 ] || printf 'mounted; proceeding.\n'
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exit 0
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@@ -46,10 +46,11 @@ view really is a mountpoint.
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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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Both consumers gate their start on the view with
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`ExecStartPre=/home/dank/serverAppConfigs/scripts/wait-for-mount.sh` (it waits
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for the mount, then refuses), and `scripts/deploy.sh dankserver --service
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jellyfin|plex` calls `media-view.sh install` + `verify` before it restarts
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either container.
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| Consumer | Bind | Mode | Why that path |
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|---|---|---|---|
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@@ -80,11 +81,20 @@ the defaults are the host values above.
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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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- **A container that binds the array must refuse to start until the mount
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answers.** Live 2026-10-31: the array's mount and the media containers raced at
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boot, podman resolved the bind against the pre-mount directory, and both
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servers came up blind — Jellyfin read an empty library and began
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`Removing item, Type: "Season"` by the thousand. Two dependencies people reach
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for do not work here, both measured on that host: `RequiresMountsFor=` in a
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**rootless** unit is inert (the user manager cannot order against the system's
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`mnt-entropy.mount`), and `ConditionPathIsMountPoint=` is fail-*dead* — an
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unmet condition logs `skipped, unmet condition check` with `NRestarts=0` and no
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start attempt ever follows, so the unit waits for a human. The working guard is
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`scripts/wait-for-mount.sh` as `ExecStartPre`: it waits out the race, refuses by
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name after its window, and `Restart=always` carries the unit from there.
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systemd does not create a mount point, so `install` creates `view` itself;
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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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@@ -107,7 +117,8 @@ the defaults are the host values above.
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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.service` / `plex.service` fail with `refused: still not mounted after 90s: …` | The view or the array is not mounted. Do not start them anyway: `scripts/media-view.sh install`, then `verify`. |
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| Servers answer, library looks empty, Jellyfin logs `Removing item, Type: "Season"` by the thousand | Blind bind — the container started before the mount and bound the pre-mount directory. `podman exec jellyfin ls /data` against `ls /mnt/entropy` is the whole diagnosis; restarting the container re-resolves the bind. |
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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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Executable
+96
@@ -0,0 +1,96 @@
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#!/usr/bin/env bash
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# Seam: a container that binds the entropy array must refuse to start until the
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# thing it binds is actually mounted.
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#
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# Live 2026-10-31, Dankserver: the array's systemd mount STARTED eight seconds
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# before the media containers were created, but a rootless quadlet cannot order
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# itself against a SYSTEM mount unit — `RequiresMountsFor=/mnt/entropy` resolves
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# to nothing in the user manager and is simply inert. So podman resolved the bind
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# against the pre-mount directory (which held one stale subdirectory) and both
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# Jellyfin and Plex came up blind: their library root looked empty, Jellyfin
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# logged thousands of `Removing item, Type: "Season"`, and the array sat at 80 %
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# util doing nothing useful until the host went down. A blind bind is not a
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# cosmetic fault — it is a metadata-deleting machine.
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#
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# The measured fix is `ExecStartPre=<repo>/scripts/wait-for-mount.sh <source>`:
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# it WAITS for the mount and then refuses, so `Restart=always` carries the unit
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# across a slow mount. A `ConditionPathIsMountPoint=` was measured on the same
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# host and is the wrong tool: an unmet condition logs `skipped, unmet condition
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# check` with NRestarts=0 and never a start attempt — the unit stays dead until
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# a human starts it. That is fail-dead, not fail-closed.
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#
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# Tests assert only observable behavior of the gate (exit status and the name it
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# refuses by) and the structural law over the quadlets; never the internals.
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load helpers
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GATE="$REPO_ROOT/scripts/wait-for-mount.sh"
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@test "the gate accepts a path that really is a mountpoint" {
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run "$GATE" -t 2 /proc
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[ "$status" -eq 0 ] || { printf '%s\n' "$output" >&2; return 1; }
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}
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@test "a plain directory is refused, and refused BY NAME" {
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dir="$BATS_TEST_TMPDIR/not-a-mount"
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mkdir "$dir"
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run "$GATE" -t 1 "$dir"
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[ "$status" -ne 0 ] || { printf 'accepted a plain directory\n' >&2; return 1; }
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[[ "$output" == *"$dir"* ]] || { printf 'refusal did not name the path: %s\n' "$output" >&2; return 1; }
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}
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@test "a path that does not exist is refused by name" {
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run "$GATE" -t 1 "$BATS_TEST_TMPDIR/does/not/exist"
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[ "$status" -ne 0 ]
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[[ "$output" == *"$BATS_TEST_TMPDIR/does/not/exist"* ]]
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}
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@test "the gate holds the deadline instead of deciding on one look" {
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# A single check that failed at the wrong instant is the boot race itself:
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# the mount lands a second later and the unit is dead anyway. So the window
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# must be spent waiting, and that is observable from outside as elapsed time.
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dir="$BATS_TEST_TMPDIR/never"
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mkdir "$dir"
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start=$SECONDS
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run "$GATE" -t 4 "$dir"
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elapsed=$((SECONDS - start))
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[ "$status" -ne 0 ]
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[ "$elapsed" -ge 4 ] || { printf 'gave up after %ss, window was 4s\n' "$elapsed" >&2; return 1; }
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}
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@test "the gate accepts a mount that arrives during its window" {
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dir="$BATS_TEST_TMPDIR/later"
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mkdir "$dir"
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if ! mount --bind /proc "$dir" 2>/dev/null; then
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skip "creating a mount needs privileges this box does not grant"
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fi
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run "$GATE" -t 4 "$dir"
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umount "$dir" 2>/dev/null || sudo -n umount "$dir" 2>/dev/null || true
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[ "$status" -eq 0 ] || { printf 'gate did not wait for a mount that arrived: %s\n' "$output" >&2; return 1; }
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}
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@test "no unit without the gate binds the array or the metadata view" {
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bad=""
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while IFS= read -r unit; do
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sources=$(sed -n 's/^Volume=\([^:]*\):.*/\1/p' "$unit" \
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| grep -E '^(/mnt/entropy|/var/lib/media-meta/view)$' | sort -u)
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[ -n "$sources" ] || continue
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for src in $sources; do
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grep -q "ExecStartPre=.*wait-for-mount.sh.* $src\b" "$unit" \
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|| bad="$bad$unit binds $src with no start gate"$'\n'
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done
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done < <(find "$REPO_ROOT"/dankserver "$REPO_ROOT"/dankclaw "$REPO_ROOT"/frankbook-pro \
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-path '*/quadlet/*.container' -not -path '*.AGENTTRASH*')
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[ -z "$bad" ] || { printf 'blind binds:\n%s' "$bad" >&2; return 1; }
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}
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@test "no gated unit keeps the fail-dead ConditionPathIsMountPoint" {
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bad=""
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while IFS= read -r unit; do
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grep -q "wait-for-mount.sh" "$unit" || continue
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grep -q "ConditionPathIsMountPoint" "$unit" \
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&& bad="$bad$unit: a gate and an unmet-condition skip cannot coexist"$'\n'
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done < <(find "$REPO_ROOT"/dankserver "$REPO_ROOT"/dankclaw "$REPO_ROOT"/frankbook-pro \
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-path '*/quadlet/*.container' -not -path '*.AGENTTRASH*')
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[ -z "$bad" ] || { printf 'fail-dead conditions:\n%s' "$bad" >&2; return 1; }
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}
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@@ -61,7 +61,10 @@ UNIT="$REPO_ROOT/dankserver/host/systemd/media-meta-view.mount"
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@test "both media servers bind the view and refuse to start without it" {
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for unit in "$JELLY" "$PLEX"; do
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grep -q "^Volume=$MOUNT:" "$unit" || return 1
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grep -q "^UnitConfigItem=ConditionPathIsMountPoint=$MOUNT$" "$unit" || return 1
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# The refusal is a start GATE, not a Condition: measured on the host, a
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# unit whose Condition goes unmet is skipped forever (NRestarts=0, no
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# start attempt) — fail-dead. The gate waits, then refuses.
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grep -q "^ExecStartPre=.*wait-for-mount.sh .*$MOUNT" "$unit" || return 1
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# The raw array must no longer be a container source: that bind is what
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# made sidecar sharing impossible (read-only) and metadata slow (seeks).
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! grep -q '^Volume=/mnt/entropy' "$unit"
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Reference in new issue
Block a user