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Fast-Docker

This repo aims to cover Docker details (Dockerfile, Image, Container, Commands, Volumes, Docker-Compose, Networks, Swarm, Stack) fastly, and possible example usage scenarios (HowTo: Applications) in a nutshell. Possible usage scenarios are aimed to update over time.

Keywords: Docker-Image, Dockerfile, Containerization, Docker-Compose, Docker-Volume, Docker-Network, Docker-Swarm, Service, Cheatsheet.

Quick Look (HowTo)

Table of Contents

Motivation

Why should we use Docker? "Docker changed the way applications used to build and ship. It has completely revolutionized the containerization world." (Ref:ItNext)

Needs

  • Installing all dependencies, setting up a new environment for SW (time-consuming every time to install environment for testing )
  • We want to run our apps on different platforms (Ubuntu, Windows, Raspberry Pi).
    • Question in our mind: What if, it does not run on a different OS?
  • CI/CD Integration Testing: We can handle unit testing, component testing with Jenkins. What if integration testing?
    • Extending Chain: Jenkins- Docker Image - Docker Container - Automatic testing
  • Are our SW products portable to carry on different PC easily? (especially in the development & testing phase)
  • Developing, testing, maintenance of code as one Monolithic App could be problematic when the app needs more features/services. It is required to convert one big monolithic app into microservices.

Benefits

  • NOT needed to install dependencies/SWs again & again
  • Enables to run on different OS, different platforms
  • Enables consistent environment
  • Enables more efficient use of system resources
  • Easy to use and maintain
  • Efficient use of the system resources
  • Isolate SW components
  • Enables faster software delivery cycles
  • Containers give us instant application portability.
  • Enables developers to easily pack, ship, and run any application as a lightweight, portable, self-sufficient container
  • Microservice Architecture (Monolithic Apps to MicroService Architecture, e.g. Cloud Native App)

(Ref: Infoworld)

Problems Docker does not solve

  • Docker does NOT fix your security issues
  • Docker does NOT turn applications magically into microservices
  • Docker isn’t a substitute for virtual machines

(Ref: Infoworld)

What is Docker?

  • Docker is a tool that reduces the gap between Development/Deployment phase of a software development cycle.
  • Docker is like VM but it has more features than VMs (no kernel, only small app and file systems, portable)
    • On Linux Kernel (2000s) two features are added (these features support Docker):
      • Namespaces: Isolate process.
      • Control Groups: Resource usage (CPU, Memory) isolation and limitation for each process.
  • Without Docker, each VM consumes 30% resources (Memory, CPU)

image (Ref: Docker.com)

Architecture

image (Ref: docs.docker.com)

Installation

Docker Engine (Deamon, REST API, CLI)

  • There are mainly 3 components in the Docker Engine:
    • Server is the docker daemon named docker daemon. Creates and manages docker images, containers, networks, etc.
    • Rest API instructs docker daemon what to do.
    • Command Line Interface (CLI) is the client used to enter docker commands.

image (Ref: Docker.com)

Docker Registry and Docker Hub

image

App: Running Docker Free Local Registry, Tagging Container, Pushing to Local Registry, Pulling From Local Registry and Deleting Images from Local Registry

Docker Command Structure

  • docker [ManagementCommand] [Command]
docker container ls -a
docker image ls
docker volume ls
docker network ls
docker container rm -f [containerName or containerID]

image

image

Docker Container

image (Ref: docker-handbook-borosan)

  • When we create the container from the image, in every container, there is an application that is set to run by default app.
    • When this app runs, the container runs.
    • When this default app finishes/stops, the container stops.
  • There could be more than one app in docker image (such as: sh, ls, basic commands)
  • When the Docker container is started, it is allowed that a single application is configured to run automatically.
docker container run --name mywebserver -d -p 80:80 -v test:/usr/share/nginx/html nginx
docker container ls -a
docker image pull alpine
docker image push alpine
docker image build -t hello . (run this command where “Dockerfile” is)
(PS: image file name MUST be “Dockerfile”, no extension)
docker save -o hello.tar test/hello
docker load -i <path to docker image tar file>
docker load -i .\hello.tar

Goto: App: Creating First Docker Image and Container using Docker File

Docker Container: Life Cycle

image (Ref: life-cycle-medium)

e.g. [imageName]=alpine, busybox, nginx, ubuntu, etc.
docker image pull [imageName]
docker container run [imageName]
docker container start [containerId or containerName]
docker container stop [containerId or containerName]
docker container pause [containerId or containerName]
docker container unpause [containerId or containerName]

Docker Container: Union File System

  • Images are read only (R/O).
  • When containers are created, new read-write (R/W) thin layer is created.

image (Ref: docs.docker.com)

Docker Volumes: Why Volumes needed?

  • Containers do not save the changes/logs when erased if there is not any binding to volume/mount.
  • For persistence, volumes/mounts MUST be used.
  • e.g. Creating a log file in the container. When the container is deleted, the log file also deleted with the container. So volumes/binding mounts MUST be used to provide persistence!

image (Ref: udemy-course:adan-zye-docker)

Docker Volumes/Bind Mounts

  • Volumes and binding mounts must be used for saving logs, output files, and using input files.
  • When volumes bind to the directory in the container, this directory and volume are synchronised.
docker volume create [volumeName]
docker volume create test
docker container run --name [containerName] -v [volumeName]:[pathInContainer] [imageName]
docker container run --name c1 -v test:/app alpine

Goto: App: Binding Volume to the Different Containers

Bind Mount

docker container run --name [containerName] -v [pathInHost]:[pathInContainer] [imageName]
docker container run --name c1 -v C:\test:/app alpine

image (Ref: Docker.com)

Goto: App: Binding Mount to Container Goto: App: Transferring Content between Host PC and Docker Container

Docker Network

  • Docker containers work like VMs.
  • Every Docker containers have network connections
  • Docker Network Drivers:
    • None
    • Bridge
    • Host
    • Macvlan
    • Overlay

Docker Network: Bridge

  • Default Network Driver: Bridge (--net bridge)
docker network create [networkName]
docker network create bridge1
docker container run --name [containerName] --net [networkName] [imageName] 
docker container run --name c1 --net bridge1 alpine sh
docker network inspect bridge1
docker container run --name c2 --net bridge1 alpine sh
docker network connect bridge1 c2
docker network inspect bridge1
docker network disconnect bridge1 c2
  • Creating a new network using customized network parameters:
docker network create --driver=bridge --subnet=10.10.0.0/16 --ip-range=10.10.10.0/24 --gateway=10.10.10.10 newbridge

image (Ref: Docker.com)

Docker Network: Host

  • Containers reach host network interfaces (--net host)
docker container run --name [containerName] --net [networkName] [imageName] 
docker container run --name c1 --net host alpine sh

image (Ref: Docker.com)

Docker Network: MacVlan

  • Each Container have own MAC interface (--net macvlan)

image (Ref: Docker.com)

Docker Network: Overlay

  • Containers which work on different PC/host can work as the same network (--net overlay)

image (Ref: Docker.com)

Port Mapping/Publish:

  • Mapping Host PC's port to container port:
-p [hostPort]:[containerPort], --publish [hostPort]:[containerPort] e.g. -p 8080:80, -p 80:80
docker container run --name mywebserver -d -p 80:80 nginx

Docker Log

  • Docker Logs show /dev/stdout, /dev/stderror
docker logs --details [containerName]

image

Docker Stats/Memory-CPU Limitations

image

image

image

Docker Enviroment Variables

image

Docker File

image

Sample Docker Files

FROM python:alpine3.7
COPY . /app
WORKDIR /app
RUN pip install -r requirements.txt
EXPOSE 5000
CMD python ./index.py
FROM ubuntu:18.04
RUN apt-get update -y
RUN apt-get install default-jre -y
WORKDIR /myapp
COPY /myapp .
CMD ["java","hello"]
  • Multistage Docker File (Creating temporary container):
    • In the example, JDK (Java Development Kit) based temporary image (~440MB) container is created for compilation.
    • Compiled files are copied into JRE (Java Runtime Environment) based image (~145MB). Finally, we have only JRE based image.
COPY --from=<stage 1> stage1/src stage2/destination
  • In the example below, 'compiler' is 'stage1'.
FROM mcr.microsoft.com/java/jdk:8-zulu-alpine AS compiler
COPY /myapp /usr/src/myapp
WORKDIR /usr/src/myapp
RUN javac hello.java

FROM mcr.microsoft.com/java/jre:8-zulu-alpine 
WORKDIR /myapp
COPY --from=compiler /usr/src/myapp .
CMD ["java", "hello"]

Docker Image

  • Create Image using Dockerfile
docker image build -t hello . (run this command where “Dockerfile” is)
(PS: image file name MUST be “Dockerfile”, no extension)
docker image pull [imageName]
docker image push [imageName]
docker image tag [imageOldName] [imageNewName]
(PS: If you want to push DockerHub, [imageNewName]=[username]/[imageName]:[version])
docker save -o hello.tar test/hello
docker load -i <path to docker image tar file>
docker load -i .\hello.tar

image

Goto: App: Creating First Docker Image and Container using Docker File

Docker Compose

  • Define and run multi-container applications with Docker.
  • Easy to create Docker components using one file: Docker-Compose file
  • It is a YAML file that defines components:
    • Services,
    • Volumes,
    • Networks,
    • Secrets
  • Sample "docker-compose.yml" file:
version: "3.8"

services:
  mydatabase:
    image: mysql:5.7
    restart: always
    volumes: 
      - mydata:/var/lib/mysql
    environment: 
      MYSQL_ROOT_PASSWORD: somewordpress
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wordpress
      MYSQL_PASSWORD: wordpress
    networks:
      - mynet
  mywordpress:
    image: wordpress:latest
    depends_on: 
      - mydatabase
    restart: always
    ports:
      - "80:80"
      - "443:443"
    environment: 
      WORDPRESS_DB_HOST: mydatabase:3306
      WORDPRESS_DB_USER: wordpress
      WORDPRESS_DB_PASSWORD: wordpress
      WORDPRESS_DB_NAME: wordpress
    networks:
      - mynet
volumes:
  mydata: {}
networks:
  mynet:
    driver: bridge
  • After saving the file as "docker-compose.yml", run the following commands where the docker-compose file is, to create containers, volumes, networks:
docker-compose up -d
docker-compose down

Goto: App: Docker-Compose File - Creating 2 Different Containers: WordPress Container depends on MySql Container

Docker Swarm

One of the Container Orchestration tool:

  • Automating and scheduling the
    • deployment,
    • management,
    • scaling, and
    • networking of containers
  • Container Orchestration tools:
    • Docker Swarm,
    • Kubernetes,
    • Mesos

image (Ref: udemy-course:adan-zye-docker)

Docker Stack / Docker Service

  • With Docker Stack, multiple services can be created with one file.
  • It is like a Docker-Compose file but it has more features than a Docker-compose file: update_config, replicas.
  • But it is running on when Docker Swarm mode is activated.
  • Network must be 'overlay'.

Creating, Listing, Inspecting

docker service create --name testservice --replicas=5 -p 8080:80 nginx
docker service ps testservice (listing running containers on which nodes)
docker service inspect testservice

Scaling

docker service scale testservice=10 (scaling up the containers to 10 replicas)

Updating

docker service update --detach --update-delay 5s --update-parallelism 2 --image nginx:v2 testservice (previous state: testservice created, now updating)
docker service update --help (to see the parameters of update)

Rollbacking

docker service rollback --detach testservice (rollbacking to previous state)

image

Goto: App: Creating Docker Swarm Cluster With 5 PCs using PlayWithDocker : 3 x WordPress Containers and 1 x MySql Container using Docker-Compose File

Play With Docker

image

Docker Commands Cheatsheet

Goto: Docker Commands Cheatsheet

Other Useful Resources Related Docker

References


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