Let’s get started with Volumes and Networks in Docker. If you are just starting with docker then I will suggest you to check my Docker for kids post.

Docker Networks

Docker networks are same as the network we have at our home. A WiFi router and multiple devices connected with it.

In case of Docker there will be Containers as devices.

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Let’s get started

First we have to create a network

$ docker network create testnet
# testnet -> name of the network
-----
# to list the networks.
# you will see your network that you created here.
$ docker network ls

Now our network is created let’s attach containers(simply devices) to it.

# two container which will automatically remove when you exit.
# Use 3 terminal windows.
# 1 for ubuntu1, 1 for ubuntu2 and 1 for other commands
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$ docker run --rm -it --name=ubuntu1 --net=testnet ubuntu
$ docker run --rm -it --name=ubuntu2 --net=testnet ubuntu

# --name -> name of the container
# --net -> name of the network in which these two container will attach.

Now a note : Docker containers in the same network can communicate with each other by container name also.

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Now let’s inspect our network to see the details about the containers that we just attached in it.

$ docker network inspect testnet
# Output (Snippet)
"Containers": {
            "4546fe405f6755cdce83c04c666710a7e0b899d688247bfae967ad973f433f58": {
                "Name": "ubuntu1",
                "EndpointID": "37c8edda8657cf486786884390ed520eee662d6461c8eeb7397b5c8b60920c19",
                "MacAddress": "02:42:ac:15:00:02",
                "IPv4Address": "172.21.0.2/16",
                "IPv6Address": ""
            },
            "e2ec3e500f29c96224a4a317170b22bf1d064f62c00fdd619e20a0d7c35d0c6a": {
                "Name": "ubuntu2",
                "EndpointID": "9dae07afdc3ca8a954843a557893d0edd426f92651bc4c553f4cc36949f843d7",
                "MacAddress": "02:42:ac:15:00:03",
                "IPv4Address": "172.21.0.3/16",
                "IPv6Address": ""
            }
        },

You will see out two containers attached in the network and their respective IP address as well.

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The next task will be to ping ubuntu1 container from ubuntu2 container.

Go to the terminal of ubuntu2 and run these commands

$ apt update && apt install iputils-ping -y
$ ping ubuntu1
# Output will be something like
# 64 bytes from bom05s09-in-f14.1e100.net (172.217.26.238): icmp_seq=4 ttl=55 time=40.1 ms

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Port | Nginx example

Suppose you have Nginx running in a container and you want to use it. Nginx listens to port 80 by default. So we have to expose the container’s port to the host machine’s port.

$ docker run --rm -it --name=ubuntu1 -p 80:8080 ubuntu
# -p -> port
# 80: -> container port
# :8080 -> host port

Great now your system is connected to the container at port 8080. Every request to that port will go to the Container ‘s port 80.

Let’s install Nginx in that container. Run this command inside the container.

$ apt update && apt install nginx -y && nginx

Our Nginx service is running now. To reverse check run this command to see if Nginx has started or not.

$ service nginx status
# Output will be something like 'service nginx is running'
Now go to your browser and type localhost:8080 in address bar.

Nginx page will be displayed !

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Docker Volume

There are volumes which are persisting data generated by and used by Docker containers and Bind mounts on the other hand are directory on your system shared with the docker container.

Volume

Create a volume.

# create a volume named testvol.
$ docker volume create testvol

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Attach this volume to our containers at root as directory named mydir.

$ docker run --rm -it -v testvol:/mydir --name=ubuntu1 ubuntu
$ docker run --rm -it -v testvol:/mydir --name=ubuntu2 ubuntu
# -v -> volume
# testvol: -> name of the volume that you created
# :/mydir -> path to attach that volume in the docker container

Now whatever you do inside mydir directory that will be shared between both of the containers

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Bind Mount

Attach a directory from your system inside a docker container by using this command

$ docker run --rm -it -v /home/username:/hello --name=ubuntu1 ubuntu
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# Syntax 
docker run -it -v <host_directory_path>:<container_path> imagename

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Docker Networks and Volumes