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Dockerfile vs docker-compose.yaml for Network Configuration
Govardhana M K
July 15, 2025
TechOps Examples
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IN TODAY'S EDITION
🧠 Use Case
Dockerfile vs docker-compose.yaml for Network Configuration
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🧠 USE CASE
Dockerfile vs docker-compose.yaml for Network Configuration
An entry level DevOps engineer on my team once explained this to me:
“In my docker-compose.yaml, I assign a static IP to a web app container like this:
networks:
custom01:
ipv4_address: x.x.x.xIt works. The app is reachable at a fixed IP, and Nginx can route traffic to it.
But the app needs to be built from source. I use a Dockerfile to install packages, build binaries, and set up the environment.
I tried assigning a network inside the Dockerfile, but it didn’t work”.
He had hit a common mistake. The Dockerfile and docker-compose.yaml solve different problems.
Dockerfile defines how the image is built. It controls what is inside the container (OS, packages, source code, build steps).
docker-compose.yaml defines how the container is run. It handles ports, volumes, networks, and container relationships.
You cannot attach a container to a network or assign it a specific IP address within a Dockerfile. That configuration is handled at runtime, typically using a docker-compose.yaml file.
The solution
Build the app image using the Dockerfile. Use docker-compose.yaml to run it with proper network settings.
services:
app:
build: ./app
networks:
custom01:
ipv4_address: 192.168.50.10
nginx:
image: nginx:alpine
volumes:
- ./nginx.conf:/etc/nginx/nginx.conf
networks:
custom01:
ipv4_address: 192.168.50.5
networks:
custom01:
external: true
Create the network first:
docker network create --driver=bridge --subnet=192.168.50.0/24 custom01Your Nginx config can then route traffic to http://192.168.50.10.
Takeaway
Use the Dockerfile to define how the image is built.
Use docker-compose.yaml to control how containers run and connect.
Network setup always belongs to the runtime, not the build phase.