Monitoring docker containers using tools like Dozzle and Uptime Kuma requires explicit configuration of the Docker daemon on the target host.

For monitoring containers on the localhost (the same host where Dozzle/Kuma are already running), one would just bind the docker.sock file to the monitoring container.

Using Docker CLI:

-v /var/run/docker.sock:/var/run/docker.sock

Using Docker Compose:

volumes:
   - /var/run/docker.sock:/var/run/docker.sock

Monitoring containers running on remote hosts is different and requires enabling and exposing the TCP port 2375 on the target host. Following are the steps I followed to expose the Docker API on a Raspberry Pi 4B running the official Debian-based OS.

Edit the file located at /etc/docker/daemon.json. If not present, create one:

nano /etc/docker/daemon.json

Add in:

{
  "hosts": ["unix:///var/run/docker.sock", "tcp://192.168.68.78:2375"]
}

This exposes the Docker API /var/run/docker.sock of the host at port 2375. The IP must exactly match what the monitoring tool will use to connect with. Also, note that this method is insecure and gives ‘root’ access to your containers, so only use within a closed network.

Now:

systemctl edit docker.service

You will see an override file for docker.service. Add the below in the uncommented space:

[Service]
ExecStart=
ExecStart=/usr/bin/dockerd

This removes additional duplicate options that were added in the previous config file.

Restart the service after reloading systemd configs.

systemctl daemon-reload
systemctl restart docker.service

Verify now with netstat:

netstat -lntp | grep dockerd

Output should look like:

tcp        0      0 192.168.68.78:2375      0.0.0.0:*               LISTEN      1955/dockerd