Summary - Network

Combine create, connect and publish to set up multi-container.

Summary: networking

In this group:

Drivers: bridge (default), host, none, overlay.
docker network ls/inspect/create/rm/prune manage networks.
On user-defined bridge networks the container name is the DNS name; on the default bridge it isn't.
network connect/disconnect attach a running container to networks; --network-alias gives an extra name.
In-network traffic uses the container port; only entry points like a reverse proxy publish ports.

docker network create arka
docker run -d --name db --network arka postgres:16
docker run -d --name api --network arka -p 8000:8000 api:1.0

Exercise A two-tier network

Write three commands: create the arka network; start a container named db from postgres:16 in the background on arka with POSTGRES_PASSWORD=gizli; start a container named api from api:1.0 in the background on arka, mapping 8000 to 8000 and with DATABASE_URL=postgresql://postgres:gizli@db:5432/postgres.

Show example solution

docker network create arka
docker run -d --name db --network arka -e POSTGRES_PASSWORD=gizli postgres:16
docker run -d --name api --network arka -p 8000:8000 -e DATABASE_URL=postgresql://postgres:gizli@db:5432/postgres api:1.0

Test yourself

What is the simplest way for two containers to find each other by name?
- Publishing both their ports
- Using --network host
- Writing their IPs into /etc/hosts by hand
- Putting both on the same user-defined network
Show answer

Putting both on the same user-defined network — Docker's built-in DNS works on user-defined networks.

Start the container on a specific network.

docker run -d --name db ____ arka postgres:16

Show answer

docker run -d --name db --network arka postgres:16

Match.

bridge

Default
DNS

On user-defined networks
connect

Attach later
-p

Open to the outside

Next lesson: Challenge - Dockerfile

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