The Docker community is a vibrant ecosystem that offers a wealth of resources for learning and collaboration:
Containers are lightweight, portable, and self-sufficient units that package an application and its dependencies:
The Docker Command Line Interface (CLI) is a powerful tool for interacting with Docker containers:
docker run (to create and start containers), docker ps (to list running containers), and docker stop (to stop containers).docker images to list images, docker pull to fetch images from Docker Hub, and docker rmi to remove images.docker exec allow you to run commands inside a running container, while docker logs helps retrieve container logs for troubleshooting.A Dockerfile is a script containing a series of instructions to build a Docker image:
FROM (to specify the base image), RUN (to execute commands), and COPY (to copy files into the image).FROM ubuntu:latest
RUN apt-get update && apt-get install -y python3
COPY . /app
CMD ["python3", "/app/app.py"]docker build command to create an image from a Dockerfile, specifying the context directory and tagging the image.Docker Compose is a tool for defining and running multi-container Docker applications:
docker-compose up to start all services defined in the compose file and docker-compose down to stop and remove them.docker-compose.yml file might look like:version: '3'
services:
web:
image: nginx
ports:
- "80:80"
db:
image: postgres
environment:
POSTGRES_PASSWORD: exampleDocker Swarm is Docker's native clustering and orchestration tool for managing a cluster of Docker nodes:
docker service commands, enabling scaling and load balancing.To install Docker on Windows, follow these steps:
docker --version to check if Docker is installed correctly.Installing Docker on Linux varies by distribution. Below are general steps for Ubuntu:
sudo apt-get update to refresh the package index.sudo apt-get install apt-transport-https ca-certificates curl software-properties-common to install necessary packages.curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -.sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable".sudo apt-get update and install Docker with sudo apt-get install docker-ce.sudo systemctl start docker to start the Docker service and sudo systemctl enable docker to enable it on boot.docker --version.To set up Docker on macOS, follow these steps:
docker --version to confirm that Docker is installed.Docker Toolbox is an older method to run Docker on Windows and Mac for users who cannot run Docker Desktop:
docker --version to confirm Docker is operational.Docker Desktop is the recommended way to run Docker on Windows and Mac:
A Dockerfile is a text document that contains all the commands to assemble an image. It is crucial for automating the image creation process.
FROM instruction, followed by commands to install dependencies, copy files, and configure the environment.FROM: Specifies the base image.RUN: Executes commands during the image build.COPY: Copies files from the host to the image.CMD: Specifies the default command to run when a container is started from the image.FROM ubuntu:latest
RUN apt-get update && apt-get install -y python3
COPY . /app
CMD ["python3", "/app/my_script.py"]To create an image from a Dockerfile, use the docker build command.
docker build -t : -t: Tags the image with a name and optional tag.--no-cache: Builds the image without using cache for the previous layers.docker build -t myapp:1.0 . (builds an image named `myapp` with the tag `1.0` from the current directory).A repository on Docker Hub or a private registry is necessary for storing your images.
docker push command to push images.Tagging helps in version control and organization of images.
docker tag : : docker tag myapp:1.0 myapp:latest (tags `myapp:1.0` as `myapp:latest`).Pushing an image to a repository allows others to access it.
docker push : docker push myapp:1.0 (pushes the image to the repository).docker login before pushing images.Docker Buildx is an experimental tool that extends Docker’s build capabilities.
docker buildx build instead of docker build.docker buildx build --platform linux/amd64,linux/arm64 -t myapp:multi . (builds for both amd64 and arm64 platforms).Running a Docker container creates an instance of an image. The container can be started using the following command:
docker run [OPTIONS] [:] -d: Run the container in detached mode (in the background).-p: Map a port on the host to a port in the container (e.g., -p 8080:80 maps port 80 in the container to port 8080 on the host).--name: Assign a name to the container (e.g., --name my_container).-e: Set environment variables in the container (e.g., -e MY_ENV=production).docker run -d -p 8080:80 --name my_webserver nginx (runs an Nginx server in the background).To manage container lifecycle, you may need to stop and remove containers.
docker stop docker stop my_webserver (stops the running container named `my_webserver`).docker rm docker rm my_webserver (removes the stopped container named `my_webserver`).-f to forcefully remove a running container (e.g., docker rm -f my_webserver).Running a container interactively allows you to execute commands directly within the container.
docker run -it docker run -it ubuntu bash (runs an Ubuntu container and opens a Bash shell).exit or use Ctrl + D to exit the interactive session.Docker provides logging features to monitor container outputs.
docker logs to view the logs.-f option to tail logs in real-time (e.g., docker logs -f my_webserver).--log-driver option when running a container.The docker inspect command provides detailed information about a container.
docker inspect --format option to filter and format the output (e.g., docker inspect --format='{{.State.Status}}' my_webserver).Health checks are a way to monitor the status of a running container.
HEALTHCHECK instruction in the Dockerfile to specify how to check the health of a container.HEALTHCHECK CMD curl --fail http://localhost/ || exit 1
INTERVAL 30s
TIMEOUT 10s
STARTUP 5sdocker inspect to view the health status of a container, which will show `healthy`, `unhealthy`, or `starting`.The default network type for Docker containers, enabling communication between containers on the same host.
docker network inspect bridge to see the details.docker network create --driver bridge my_bridge--network my_bridge when running a container to connect it to the custom bridge.This mode allows containers to share the host's networking stack, which can be useful for performance.
docker run --network host Overlay networks allow containers running on different Docker hosts to communicate with each other, making it essential for multi-host networking in Swarm mode.
docker network create --driver overlay my_overlay
Macvlan networks allow you to assign a unique MAC address to a container, making it appear as a physical device on the network.
docker network create -d macvlan --subnet=192.168.1.0/24 --gateway=192.168.1.1 -o parent=eth0 my_macvlan
Docker allows you to publish container ports to the host, enabling external access to containerized services.
docker run -p : docker run -p 8080:80 nginx (maps port 80 in the container to port 8080 on the host).http://localhost:8080 in a browser.Docker Compose simplifies the process of managing networks for multi-container applications.
docker-compose.yml file, you can define networks for your services:
version: '3'
services:
web:
image: nginx
networks:
- my_network
db:
image: postgres
networks:
- my_network
networks:
my_network:Docker Swarm is Docker’s native clustering and orchestration tool, enabling users to manage multiple Docker hosts as a single virtual host. It provides high availability, load balancing, and scaling of containerized applications.
To create a Swarm, you need to initialize a manager node and can then add worker nodes to the swarm.
docker swarm initdocker swarm init output, which looks like:
docker swarm join --token : docker node ls to view the nodes in the swarm and their status.Once the swarm is created, you can manage it effectively through various commands.
docker node promote docker node rm docker node update --availability drain Creating services in Docker Swarm allows you to deploy containerized applications across the swarm.
docker service create --name --replicas Example:
docker service create --name web --replicas 3 nginxdocker service scale = docker service update --image Docker Content Trust (DCT) provides the ability to enforce image signing and verification in Docker. This ensures that only trusted images are pulled and run in your environment.
docker trust sign to sign an image, creating a digital signature.DOCKER_CONTENT_TRUST environment variable to 1. This will ensure images are verified before being pulled or run.User namespaces allow you to map the container user IDs to different user IDs on the host. This adds an additional layer of security by isolating user privileges.
/etc/docker/daemon.json) to enable user namespaces:
{
"userns-remap": "default"
}AppArmor and Seccomp are Linux kernel security modules that provide mandatory access control and system call filtering for Docker containers.
docker run --security-opt apparmor= docker run --security-opt seccomp= Docker Bench for Security is a script that checks for dozens of common best practices around deploying Docker containers in production.
docker run --rm -it --net host --pid host --cap-add audit_control \
--security-opt apparmor=unconfined \
docker/docker-bench-securityDocker Secrets allows you to securely store and manage sensitive information such as passwords and API keys.
echo "my_secret" | docker secret create my_secret -docker service create --name my_service --secret my_secret Docker Scan is a command that allows you to analyze images for known vulnerabilities.
docker scan AWS provides robust support for Docker containers through several services, enabling developers to deploy and manage containerized applications seamlessly.
Microsoft Azure offers various services and tools to run Docker containers, providing a flexible and powerful environment for containerized applications.
Google Cloud Platform (GCP) provides comprehensive support for Docker containers through various managed services and tools.
Digital Ocean offers a simple and straightforward way to deploy and manage Docker containers, making it ideal for developers and small businesses.
Kubernetes is an open-source container orchestration platform designed to automate deploying, scaling, and operating application containers. Its architecture is composed of several key components:
Kubernetes manages various resources to run applications effectively:
Understanding pods and services is crucial for deploying applications in Kubernetes:
Setting up a local Kubernetes environment using Docker is straightforward. Here are the steps:
minikube startminikube dashboardkubectl apply -f your-application.yamlkubectl expose deployment nginx --type=LoadBalancer --port=80Jenkins is a popular open-source automation server that facilitates CI/CD integration with Docker:
docker run -p 8080:8080 -p 50000:50000 jenkins/jenkinspipeline {
agent {
docker {
image 'node:14'
args '-p 3000:3000'
}
}
stages {
stage('Build') {
steps {
sh 'npm install'
}
}
stage('Test') {
steps {
sh 'npm test'
}
}
stage('Deploy') {
steps {
sh 'docker build -t myapp:latest .'
sh 'docker run -d myapp:latest'
}
}
}
}Travis CI is a cloud-based CI service that integrates seamlessly with Docker:
language: docker
services:
- docker
before_install:
- docker build -t myapp .
script:
- docker run myapp npm test
deploy:
provider: script
script: docker push myapp
on:
branch: mainGitLab CI/CD provides integrated CI/CD capabilities, allowing for easy Docker integration:
image: docker:latest
services:
- docker:dind
stages:
- build
- test
- deploy
build:
stage: build
script:
- docker build -t myapp .
test:
stage: test
script:
- docker run myapp npm test
deploy:
stage: deploy
script:
- docker push myappGitHub Actions is a powerful CI/CD feature integrated into GitHub, enabling Docker workflows:
name: Docker CI
on:
push:
branches:
- main
jobs:
build:
runs-on: ubuntu-latest
steps:
- name: Checkout code
uses: actions/checkout@v2
- name: Build Docker image
run: |
docker build -t myapp .
- name: Run tests
run: |
docker run myapp npm test
- name: Push Docker image
uses: docker/build-push-action@v2
with:
context: .
push: true
tags: myapp:latestDebugging Docker containers is crucial for identifying issues and ensuring applications run smoothly:
docker exec command to open a shell inside a running container:
docker exec -it /bin/bash docker logs docker inspect to get detailed information about container configurations:
docker inspect Monitoring Docker performance helps maintain application efficiency:
docker stats command to view real-time metrics for running containers:
docker statsUnderstanding Docker metrics is key for performance optimization:
docker run --memory="512m" --cpus="1" myappEffective log management is essential for troubleshooting and performance monitoring:
"log-driver": "json-file",
"log-opts": {
"max-size": "10m",
"max-file": "3"
}docker logs command to retrieve logs for specific containers.Regular garbage collection helps reclaim disk space used by unused images and containers:
docker system prune command to remove stopped containers, unused networks, and dangling images:
docker system prune -aOptimizing Dockerfiles can lead to smaller image sizes and faster builds:
FROM node:14 AS builder
WORKDIR /app
COPY . .
RUN npm install
RUN npm run build
FROM nginx:alpine
COPY --from=builder /app/build /usr/share/nginx/html.dockerignore file to exclude unnecessary files from the build context, reducing image size:
node_modules
*.log
.DS_StoreDocker volumes are a preferred way to manage persistent data generated by and used by Docker containers:
docker volume create command to create a new volume:
docker volume create my_volume-v flag:
docker run -v my_volume:/data myappdocker volume ls
docker volume inspect my_volume
docker volume rm my_volumeBind mounts allow you to link a host directory to a container, providing more flexibility but with fewer safety features compared to volumes:
-v flag to link a host directory to a container:
docker run -v /host/path:/container/path myappTemporary filesystems are useful for storing transient data that does not need to persist:
docker run --tmpfs /tmp:rw,size=100m myappStorage drivers manage the storage of images and containers and dictate how the filesystem interacts with the Docker daemon:
overlay2, aufs, and devicemapper.overlay2 is widely recommended for its performance and compatibility.docker info | grep 'Storage Driver'Docker uses a layered filesystem to efficiently manage images and reduce storage space:
docker history to inspect the layers of an image:
docker history my_image