Mount Volumes from Another Service

Some services need read-only access to files from another service — media files from a file manager, TLS certificates from a Lightning node, or shared data directories. Mount a dependency’s volume into your container.

Solution

In the Mounts chain in setupMain(), use .mountDependency() typed against the dependency’s manifest. Specify the dependency’s volumeId, a subpath (or null for the whole volume), a mountpoint in your container, and readonly: true. In dependencies.ts, declare the dependency with kind: 'exists' (if you just need the files) or kind: 'running' (if the dependency must be active).

A read-only mount of a subpath that doesn’t exist fails, which makes a throwaway one an existence check: mount it in sdk.SubContainer.withTemp() and treat a failure as missing. Only a read-only mount works for this — a read-write one creates the missing folder on the dependency’s volume and succeeds.

Reference: Dependencies · Main

Examples

See startos/main.ts and startos/dependencies.ts in: jellyfin (NextExplorer + FileBrowser Quantum + Nextcloud media), helipad (LND macaroons/certs), ride-the-lightning (LND + CLN + Eclair volumes), lightning-terminal (LND certs), albyhub (LND, CLN, or phoenixd volume)

For the existence check, see canMount in audiobookshelf’s startos/utils.ts and checkSubpathExists in navidrome’s startos/actions/mediaSources.ts.