... and create a persistent named Docker volume upon first start (if that volume does not yet exist). This volume is always created with root permission. Failing to change the permissions of /elk/data inside this volume to UID: GID 911 (as specified for Elk in the Dockerfile) will prevent Elk from storing its config for user accounts. You either have to fix the permission in the created named volume, or mount a directory with the correct permission to /elk/data into the container.