Volume and network
- Docker & Kubernetes course
- Beginner
- Lesson 64/82
- 4 min
Add volume and network definitions to the compose file.
Volumes and networks
By default Compose puts all services on a single proje_default network. To separate tiers, custom networks are defined: only the API is on both the outer and inner networks; the database stays on a network unreachable from outside:
services:
web:
image: nginx:alpine
networks: [on]
api:
build: .
networks: [on, arka]
db:
image: postgres:16
networks: [arka]
networks:
on:
arka:
internal: true # no outbound access eitherBind mounts and read-only config
To mount configuration files into services, a relative path is used in the short syntax; the path is relative to the compose file's folder:
web:
image: nginx:alpine
volumes:
- ./nginx.conf:/etc/nginx/conf.d/default.conf:ro
- statik:/usr/share/nginx/html
volumes:
statik:docker compose down doesn't delete volumes; down -v deletes them too (data loss!).
Practice Tiered networks
Write a compose.yaml: the api service is built with build: . and is on the on and arka networks; the db service uses the postgres:16 image and is only on the arka network. Under a top-level networks:, define the on: network and the arka: network with internal: true.
Starter code
# compose.yaml
# buraya yazSample solution
# compose.yaml
services:
api:
build: .
networks:
- on
- arka
db:
image: postgres:16
networks:
- arka
networks:
on:
arka:
internal: trueExpected output
[+] Running 4/4 ✔ Network proje_on Created ✔ Network proje_arka Created ✔ Container proje-db-1 Started ✔ Container proje-api-1 Started
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 In the file above, can the web service reach the db service?
- Yes, always
- Only if the port is published
- Only by IP
- No, they share no network Correct answer
Explanation: Containers talk only over the networks they share.
2 Close the network to the outside world.
networks:
arka:
____: truenetworks:
arka:
internal: trueExplanation: Containers on an internal network can't reach the outside.
3 Match.
| Term | Meaning |
|---|---|
proje_default |
Default network |
internal: true |
Network closed to the outside |
./nginx.conf:...:ro |
Read-only config |
down -v |
Also deletes volumes |