When we would like to install new app server and use old DB, we have to:

1. Migrate the .env credentials files for each of the MI services (all files under /opt/mi/config/deployment/credentials)
2. Run installer on new server (old credentials will be reused because of previous step)
3. Stop MI (mi-control stop)
4. Migrate /opt/mi/data/iv  from old server (or, instead it is also it is possible to use mi-app-backup -I files), certificate if needed, config files in /opt/mi/external_config/(crontab, saml.php)
5. Check also /opt/mi/data/custom/, maybe there can be custom scripts, etc.
6. Start MI (mi-control up -d)