Docker Course

Welcome to the Docker Academy on TechLearningPRO — a production-grade journey from your very first docker run to designing multi-service containerized systems that ship at compa…

Docker is an open-source platform for building, shipping and running applications inside containers — lightweight, isolated processes that share the host OS kernel.

VMs and containers both isolate workloads — but at different layers of the stack.

Docker uses a client-server architecture.

Getting Docker installed correctly is the foundation of every later lesson.

The traditional first program in any tech is 'Hello World'.

Master a dozen commands and you can do 95% of daily Docker work.

Docker Desktop bundles the engine, CLI, Compose, Kubernetes, Buildx and a visual UI into one installer for Mac and Windows.

A Docker image is a read-only blueprint for a container — a stack of filesystem layers packaged in the OCI format.

docker run is the workhorse: it pulls the image if needed, creates a container, attaches it to networks/volumes, and starts the main process.

Every container moves through a predictable lifecycle: created → running → paused/stopped → removed.

Sometimes you need to peek inside a running container — debug, inspect files, run a one-off command.

Observability starts with three commands.

Stopped containers, dangling images and orphan volumes silently eat disk.

A registry is a storage service for Docker images.

Docker Hub is the world's largest public image registry — official base images (nginx, node, postgres) live here.

A Dockerfile is a text recipe describing how to build an image.

When you run docker build ., the dot is the build context — the directory tree sent to the daemon.

Each Dockerfile instruction creates a cacheable layer.

Multi-stage builds let you use one image to compile/build and a smaller image to run — the build tools never ship to production.

ARG values exist only at build time; ENV values are baked into the image and visible at runtime.

HEALTHCHECK tells Docker how to know if your container is actually working — not just running.

ENTRYPOINT defines the executable; CMD provides the default args.

Smaller images deploy faster, cost less to store/transfer, expose less attack surface and start quicker.

Docker creates a virtual network for containers so they can talk to each other and the outside world.

User-defined bridge networks are the bread and butter of multi-container apps.

Containers run on isolated networks; reaching them from the host requires publishing a port.

Container filesystems are ephemeral — delete the container and data inside dies with it.

A bind mount attaches a host directory directly into the container.

Named volumes are Docker-managed storage.

Beyond bridge, Docker supports overlay (multi-host), macvlan (containers with real network IPs) and custom IPAM.

Docker runs an embedded DNS server on user-defined networks.

Docker Compose defines and runs multi-container apps with a single YAML file.

The Compose spec is rich: services, networks, volumes, configs, secrets, profiles, healthchecks, deploy hints.

A real Compose stack might be 5–15 services: web, api, db, cache, queue, worker, search, monitoring.

Compose reads .env from the project root and substitutes ${VAR} in the YAML.

docker compose up --scale worker=5 runs five copies of a worker behind the same Compose network.

Swarm mode turns multiple Docker hosts into a single cluster.

Kubernetes is the de facto orchestrator.

Compose v2 can run small production workloads on a single VM — perfect for side projects, internal tools, and MVPs that don't need Kubernetes complexity.

Containers share the host kernel — a container escape can become a host compromise.

Every image you build inherits the vulnerabilities of its base layers and dependencies.

Secrets must NEVER live in images, build args, or commits.

Without limits, one runaway container can starve the host.

Production needs centralized logs and metrics.

Modern CI builds, scans, signs and pushes images on every commit.

When things go sideways, follow a methodical playbook: check the daemon, the container, the logs, the network, the disk.

Senior Docker interviews probe both conceptual understanding (namespaces, cgroups, OCI) and practical fluency (Dockerfile authoring, debugging, networking).