Merge pull request #18 from trekie86/master

Add documentation on monitoring Docker via TCP

How-to-Monitor-Docker-Containers.md

@@ -20,7 +20,45 @@ volumes:
 
 ### (Method 2) TCP - Bridge Mode
 
-TODO
+**Expose TCP port**  
+To enable TCP monitoring, you need to first expose the Docker daemon on a TCP port. The primary documentation is available [here](https://docs.docker.com/config/daemon/) but the example below provides some quick options.
+
+Update the daemon configuration located at `/etc/docker/daemon.json`:
+```json
+{
+   #any additional parameters should be kept
+
+   #Insecure option, only use this if you are running on a closed network
+   "hosts": ["unix:///var/run/docker.sock","tcp://<host IP address>:2375"]
+
+   #Secure option
+   "tls": true,
+   "tlscert": "/var/docker/server.pem",
+   "tlskey": "/var/docker/serverkey.pem",
+   "hosts": ["unix:///var/run/docker.sock","tcp://<host IP address>:2376"]
+}
+```
+
+Restart the daemon using `sudo systemctl restart docker.service`.
+
+If the daemon fails to start, it may be because there are duplicate keys, in this case hosts, -H, that is already part of the daemon configuration.
+
+You can edit the startup configuration using `sudo systemctl edit docker.service`.
+
+```toml
+[Service]
+#The blank ExecStart is required to clear the current entry point
+ExecStart=
+#Replace the existing ExecStart but only remove the properties that you have added into the daemon.json file, leave all else the same.
+ExecStart=/usr/bin/dockerd --containerd=/run/containerd/containerd.sock
+```
+
+My original ExecStart was: `ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock`, note the -H that would cause a duplicate property error.
+
+**Update uptime-kuma**  
+Add a new Docker host and choose TCP as the option. Specify the IP address of the host and the TCP port you exposed, as seen below.
+
+![Docker host monitor](img/docker-host.png)
 
 ## Related Disscussion