The image comes from the Connectical container project endorsed by the Polaris installation guide.
Open the configured HTTP port, create an administrator, and add /music as the collection directory.
Music is mounted read-only. Cache and application data are owned by Polaris UID/GID 100:100.
Application data includes accounts, playlists, the collection index, and the application database. Back it up before upgrading.
Uninstalling the app does not delete music, cache, or application data.

Data directories

Variable	Purpose	Default
`POLARIS_MUSIC_DIR`	Read-only music library	`./data/music`
`POLARIS_CACHE_DIR`	Scan and artwork cache	`./data/cache`
`POLARIS_DATA_DIR`	Accounts, index, and database	`./data/data`

The initialization script rejects symbolic links in configured directories and recursively assigns cache and data ownership to 100:100. Use dedicated directories for Polaris.

References

Website: https://polaris.stream
Source: https://github.com/agersant/polaris
Container documentation: https://github.com/ogarcia/docker-polaris