10 Docker Networks Intro - dchantzis/sfh-docker-in-development-part-1 GitHub Wiki

Source: https://serversforhackers.com/c/div-docker-networks-intro

We will see how we can get containers to talk to each other over a Docker network.

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We will create two containers and add them into the new network appnet.

The containers then can reference eachother - the hostname for each container is taken from the --name given to the container. This lets the app container talk to mysql over hostname mysql. Within the container, you can run getent hosts mysql to see the hostname resolution of hostname mysql

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To list the default Docker networks:

docker network ls

Below we will create a new network and create two additional containers and make them communicate with each other.

docker network create appnet

docker network ls

We will create a MySQL Container and hook it up with the application container so that they can communicate with each other:

We will go to https://hub.docker.com/_/mysql and use the MySQL 5.7

docker run --rm -d --name=mysql --network=appnet -e MYSQL_ROOT_PASSWORD=root -e MYSQL_DATABASE=homestead -e MYSQL_USER=homestead -e MYSQL_USER_PASSWORD=secret mysql:5.7

• --name The name of the host

We can check everything:

docker image ls

docker network ls

docker network inspect appnet

The last command will show us the containers inside the appnet network. We can check the IPv4 Address used for the host that we named mysql

Next:

docker exec -it mysql bash

which mysql

getent hosts mysql

mysql -h mysql -u root -p

• -h Is the host that we named mysql inside the container

Now we will create the second Container under the same network appnet:

docker run --name=app --network=appnet -d --rm -p 80:80 -v %cd%/application:/var/www/html/public shippingdocker/app:latest 

To see them both running (mysql and app):

docker ps

Bash into app:

docker exec -it app bash

Then check the IP address of the host app:

getent hosts app

Check the IP address of the host mysql (this means they can see each other):

getent hosts mysql

Exit the container and inspect the network appnet to view both of the Containers of the network:

docker network inspect appnet