PostgreSQL fails to start when configured to listen on 0.0.0.0 instead of 127.0.0.1

When deploying the PostgreSQL service on Kali Linux, the objective is to restrict its network interface to the localhost address only, thereby preventing unintended exposure to external networks. The service’s configuration includes a setting that determines the IP addresses on which it accepts connections.

Because the default value for this setting can differ between package versions and may be overridden during manual tuning, there is uncertainty about whether the instance remains bound solely to 127.0.0.1 after adjustments. Administrators need to be certain that no external interface is inadvertently opened.

• Which configuration directive controls the listening address for PostgreSQL?
• What verification approach confirms that the service is not listening on any external address?