title: Mosquitto isn't loading configuration files from conf.d
body: <p>I've installed mosquito v2.0.11 on raspberry Pi3. I've written configuration file, allowing  anonymous connections, but mosquitto seems to not load this configuration.</p>
  <p><strong>/etc/mosquitto/conf.d/custom.conf:</strong></p>
  <pre><code>listener 1883
  allow_anonymous true
  </code></pre>
  <p>When I run &quot;mosquitto&quot; in bash, output looks like this:</p>
  <pre><code>1636892708: mosquitto version 2.0.11 starting
  1636892708: Using default config.
  1636892708: Starting in local only mode. Connections will only be possible from clients running on this machine.
  1636892708: Create a configuration file which defines a listener to allow remote access.
  1636892708: For more details see https://mosquitto.org/documentation/authentication-methods/
  1636892708: Opening ipv4 listen socket on port 1883.
  1636892708: Error: Address already in use
  1636892708: Opening ipv6 listen socket on port 1883.
  1636892708: Error: Address already in use
  </code></pre>
  <p>And &quot;systemctl status mosquitto.service&quot; says that congfig file was loaded. Still anonymous connections doesn't work.</p>
  <pre><code>mosquitto.service - Mosquitto MQTT Broker
       Loaded: loaded (/lib/systemd/system/mosquitto.service; enabled; vendor preset: enabled)
       Active: active (running) since Sun 2021-11-14 11:59:18 GMT; 27min ago
         Docs: man:mosquitto.conf(5)
               man:mosquitto(8)
      Process: 471 ExecStartPre=/bin/mkdir -m 740 -p /var/log/mosquitto (code=exited, status=0/SUCCESS)
      Process: 481 ExecStartPre=/bin/chown mosquitto /var/log/mosquitto (code=exited, status=0/SUCCESS)
      Process: 482 ExecStartPre=/bin/mkdir -m 740 -p /run/mosquitto (code=exited, status=0/SUCCESS)
      Process: 483 ExecStartPre=/bin/chown mosquitto /run/mosquitto (code=exited, status=0/SUCCESS)
     Main PID: 484 (mosquitto)
        Tasks: 1 (limit: 1597)
          CPU: 793ms
       CGroup: /system.slice/mosquitto.service
               └─484 /usr/sbin/mosquitto -c /etc/mosquitto/mosquitto.conf
  
  Nov 14 11:59:18 raspberrypi systemd[1]: Starting Mosquitto MQTT Broker...
  Nov 14 11:59:18 raspberrypi mosquitto[484]: 1636891158: Loading config file /etc/mosquitto/conf.d/custom.conf
  Nov 14 11:59:18 raspberrypi systemd[1]: Started Mosquitto MQTT Broker.
  </code></pre>
  <p>When I specify config file, by &quot;mosquitto -c /etc/mosquitto/conf.d/custom.conf&quot;, configuration file is loaded properly.
  I don't really know how to make it work.</p>