fix(start-core): refuse a dependency mount whose volume does not exist - #3961
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`Bind::pre_mount` creates a missing source for a read-write bind, which is right for a package's own subpaths but wrong for a pointer mount: with the dependency not installed, the effect created `volumes/<dep>/data/<vol>` on the host as a plain directory and bound it, so the dependent started against an empty folder with only the dependency warning to say so. When the dependency was installed later, `ensure_volume_root` adopted that orphan as its live root, leaving it a directory rather than a subvolume — so `InstallBackup::snapshot` has nothing to snapshot and the package gets no rollback point on update. The mount now fails with a localized error naming the missing volume when the dependency's volume root does not exist, matching what a read-only mount already did. A missing subpath inside an existing volume is still created for a read-write mount. Observed with paperless-startos pointing its consume folder at a FileBrowser Quantum that had been uninstalled. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
dr-bonez
approved these changes
Sep 16, 2026
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Summary
mountDependencyof a dependency that isn't installed used to succeed:Bind::pre_mountcreates a missing source for read-write binds (disk/mount/filesystem/bind.rs), so the pointer-mount effect (service/effects/dependency.rs::mount) createdvolumes/<dep>/data/<vol>on the host as a plain directory and bound it. The dependent started against an empty folder; the only signal was the dependency warning.ensure_volume_root(volume.rs) found the directory present and adopted it as the live root — a plain directory, not a btrfs subvolume — soInstallBackup::snapshotreturns false for that package and updates get no rollback point.NotFoundnaming the package and volume, which is what a read-only mount already did (no source is created for those, somount --rbindfailed). A missingsubpathinside an existing volume is still created for read-write mounts, as before.mountDependencydoc comment state the failure mode.Observed
On the dev box with paperless-startos (Start9-Community/paperless-startos#9) pointing its consume folder at FileBrowser Quantum's
datavolume: uninstall FileBrowser, start Paperless → it starts, and inside the container/mnt/filebrowseris a fresh empty directory on the package-data filesystem (subvol=/, i.e. not a volume subvolume) —volumes/filebrowser/now exists on the host with no package owning it.Not built locally (start-core); CI does that.
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