In the latest https://docs.openstack.org/neutron/pike/install/controller-install-ubuntu.html (Install Guide) to populate Neutron database one is instructed to run: neutron-db-manage --config-file /etc/neutron/neutron.conf --config-file /etc/neutron/plugins/ml2/ml2_conf.ini upgrade head with the following comment: "Database population occurs later for Networking because the script requires complete server and plug-in configuration files."

Is it still the case that DB migrations require the configuration files populated with all plugin and ml2 configurations?

https://docs.openstack.org/neutron/latest/contributor/alembic_migrations.html (This Neutron document) indicates that the following command should be executed: neutron-db-manage --database-connection <connection> <commands>, or neutron-db-manage --config-file /path/to/neutron.conf <commands> only to get connection from neutron.conf.

Also the blueprint https://blueprints.launchpad.net/neutron/+spec/db-migration-refactor (Neutron DB Migration Refactor) is in implemented status since 2014, and it states: "Currently the neutron database schema is dependent on the neutron configuration. It differs depending on core plugin and services configured... We need to make the database schema independent of configuration"