Master Docker: From Basics to Advanced Container Management

Introduction

Docker, originally an internal project of dotCloud and written in Go, provides lightweight OS-level virtualization that dramatically speeds up software development and deployment. It replaces traditional virtual machines with containers that share the host kernel, offering higher resource efficiency and faster startup.

Quick Start

Docker began as an internal hobby project.

It is built with Go.

Its goal is a lightweight OS virtualization solution.

It is based on Linux containers (LXC) and similar technologies.

Containers start in seconds, far faster than VMs.

A single host can run thousands of containers.

Main Advantages

Faster delivery and deployment – containers are the smallest unit.

More efficient virtualization – kernel‑level.

Easier migration and scaling.

Simpler management.

Installation

Official documentation provides installation guides for Mac, Linux, and Windows. Follow the official steps; no additional details are needed here.

Kitematic (Visual Docker Container Management on Mac & Windows) is a helpful GUI tool for beginners.

Daemon

Run the Docker daemon with custom bind options, e.g., sudo /usr/bin/docker -d -H tcp://0.0.0.0:2375. To avoid typing this each time, set the environment variable export DOCKER_HOST="tcp://0.0.0.0:2375".

Graphical User Interface

Common web management interfaces include Shipyard and Portainer.

Basic Concepts

The three core concepts are:

Image : a read‑only template used to create containers; layered via a Union file system.

Container : a running instance created from an image, with its own writable layer, isolated processes, and its own root file system.

Registry : a storage location for images, public (Docker Hub) or private.

What Docker Can Do

Standardize, optimize, and accelerate local development and build pipelines.

Ensure consistent results across environments.

Create isolated test environments.

Isolation Types

File‑system isolation – each container has its own root FS.

Process isolation – separate process spaces.

Network isolation – separate virtual interfaces and IPs.

Resource isolation – cgroups allocate CPU, memory, etc.

Common Commands

sudo docker info

– view Docker status. docker ps – list running containers ( -a for all, -l for the latest).

Simple Example

Create and run a container: docker run ubuntu:14.04 /bin/echo 'Hello wdx!' The command prints Hello wdx! as expected.

Start an interactive bash session: docker run -t -i ubuntu:14.04 /bin/bash Options: -t allocates a pseudo‑TTY, -i keeps STDIN open.

Running Commands Inside a Container

cat /etc/hosts

ip a

ps -aux

cd ~ && echo "hello wdx" > hello.txt && cat hello.txt

After exiting, the container still exists and can be inspected with docker ps -l.

Images

Pull images from a registry: sudo docker pull ubuntu:12.04 Specify a custom registry if needed, e.g., sudo docker pull dl.dockerpool.com:5000/ubuntu:12.04.

List local images:

docker images

Running an Image

Example with the whalesay image: docker run docker/whalesay cowsay boo The container prints a whale saying “boo”.

Building an Image

Create a Dockerfile:

FROM docker/whalesay:latest
RUN apt-get -y update && apt-get install -y fortunes
CMD /usr/games/fortune -a | cowsay

Build the image: sudo docker build -t wdx-whale . Verify with docker images.

Pushing to a Registry

Tag the image: docker tag 26ac9649d7da wdxtub/wdx-whale:latest Login and push:

docker login --username=wdxtub [email protected]
docker push wdxtub/wdx-whale

Managing Images

Export an image to a tar file:

docker save -o wdx-local-whale.tar wdxtub/wdx-whale

Import it back: docker load --input wdx-local-whale.tar Remove dangling images:

sudo docker rmi $(docker images -q -f "dangling=true")

Import/Export and Deletion

Export a container:

docker export <span>containerid</span> > container.tar

Import a container snapshot as an image:

cat ubuntu.tar | sudo docker import - test/ubuntu:v1.0

Delete containers:

docker rm <span>containerid</span>
# Remove all stopped containers
docker rm $(docker ps -a -q)

Registry

A registry stores images; Docker Hub is the public registry, while private registries can be set up for internal use.