Docker for Cloud Engineers

Build reproducible images, run isolated application processes, and operate them safely.

Docker packages an application and its runtime filesystem into an image. A container is a running process created from that image. Containers share the host kernel; they are not small virtual machines.

The parts you operate

Object	Purpose	Expected lifetime
Image	Read-only application template	Versioned and published
Container	Running process created from an image	Replaceable
Registry	Stores and distributes images	Long-lived service
Volume	Stores data outside a container layer	Survives replacement
Network	Connects containers and controls exposure	Project or platform scope

Application code belongs in the image. Runtime state belongs in a managed database, object store, or volume with a tested backup process.

Learning path

1 · FoundationImages and buildsCreate a small, non-root image and understand its layers, cache, tags, and digest.2 · IntermediateCompose applicationsDefine services, health checks, networks, secrets, and persistent data.3 · IntermediateContainer operationsInspect failures, deploy immutable versions, back up data, and clean up safely.

Verify the engine

Install Docker Engine and the Compose plugin from Docker’s current instructions for your operating system. Then inspect the client and server separately:

Terminal

docker version
docker info
docker compose version
docker context show

docker version confirms that the client can reach an engine. docker context show matters when a workstation can control more than one local or remote daemon.

Run one disposable container

Terminal

docker run --name web-demo --rm -d \
  -p 127.0.0.1:8080:80 \
  nginx:alpine

curl -I http://127.0.0.1:8080
docker logs web-demo
docker stop web-demo

Binding to 127.0.0.1 keeps the published port local to the host. The image tag is convenient for this disposable exercise; production releases should use an approved version and record the resolved image digest.

Docker access is privileged

On a conventional rootful engine, users who can control the Docker daemon can normally obtain host-level access. Grant daemon access only to trusted operators. Do not mount the Docker socket into application containers.

The parts you operate

Learning path

Verify the engine

Run one disposable container

References

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