my-notes

Containers With Docker

1. What is a Container

Where do containers live?

How containers improved Application Development

Before containers

After containers

Other Container Technologies

Docker is just the most popular container technology, but there are others, like:

2. Container vs. Image

What is a container?

Docker Image

Docker Container

Analogy: OOP -> Image is the class, containers are the objects.

3. Docker vs. Virtual Machine

My words:

4. Docker Architecture and Components

Alternatives for Docker

5. Main Docker Commands

# list locally available images
docker image ls

# list running containers
docker container ls
docker ps

# list all available containers
docker container ls -a
docker ps -a

# create and run a container based on an image
docker container run redis
docker container run redis:4.0  # specify the version

# create and run a container in detach mode
docker container run --detach redis
docker container run -d redis

# start an existing created container
docker container start container_name

# stop a running container
docker container stop container_name

Container Port vs. Host Port

# host port: 6000
# container port: 6379
docker container run --publish 6000:6379 redis
docker container run -p 6000:6379 redis

# host port: 6001
# container port: 6379
docker container run --publish 6001:6379 redis:4.0

6. Debug Commands

# see the latest logs from a running container
docker container logs containerName

# execute a command in a running container
docker container exec containerName command

# start a shell session in a running container
docker container exec -it containerName /bin/bash
# using `env` to see the environment variables is quite useful

7. Docker Demo - Project Overview

Workflow with Docker

workflow with docker

8. Developing with Docker

# get project's source file from:
# https://gitlab.com/nanuchi/developing-with-docker
git clone git@gitlab.com:nanuchi/developing-with-docker.git

# get MongoDB image
docker pull mongo

# get MongoDB frontend
docker pull mongo-express


# list available docker networks
docker network ls

# create a new network
docker network create mongo-network

MongoDB containers

# https://hub.docker.com/_/mongo
# create a MongoDB container defining the root username/password
docker run \
  -p 27017:27017 \
  --detach \
  -e MONGO_INITDB_ROOT_USERNAME=admin \
  -e MONGO_INITDB_ROOT_PASSWORD=password \
  --name mongodb \
  --net mongo-network \
  mongo

# https://hub.docker.com/_/mongo-express
# create the Mongo Express container
docker run \
  -p 8081:8081 \
  --detach \
  -e ME_CONFIG_MONGODB_ADMINUSERNAME=admin \
  -e ME_CONFIG_MONGODB_ADMINPASSWORD=password \
  -e ME_CONFIG_MONGODB_SERVER=mongodb \
  --net mongo-network \
  --name mongo-express \
  mongo-express

9. Docker Compose - Run multiple Docker containers

Comparison between docker run command and Docker compose yaml config:

docker run commands:

# mongodb
docker run \
  -p 27017:27017 \
  --detach \
  -e MONGO_INITDB_ROOT_USERNAME=admin \
  -e MONGO_INITDB_ROOT_PASSWORD=password \
  --name mongodb \
  --net mongo-network \
  mongo

# mongo-express
docker run \
  -p 8081:8081 \
  --detach \
  -e ME_CONFIG_MONGODB_ADMINUSERNAME=admin \
  -e ME_CONFIG_MONGODB_ADMINPASSWORD=password \
  -e ME_CONFIG_MONGODB_SERVER=mongodb \
  --net mongo-network \
  --name mongo-express \
  mongo-express

mongo.yaml:

version: '3'
services:
  mongodb: # --name
    image: mongo
    ports: # --publish
      - 27017:27017
    environment: # -e
      - MONGO_INITDB_ROOT_USERNAME=admin
      - MONGO_INITDB_ROOT_PASSWORD=password

  mongo-express: # --name
    image: mongo-express
    ports: # --publish
      - 8081:8081
    environment:
      - ME_CONFIG_MONGODB_ADMINUSERNAME=admin
      - ME_CONFIG_MONGODB_ADMINPASSWORD=password
      - ME_CONFIG_MONGODB_SERVER=mongodb

# Docker Compose takes care of creating a common network!

Install docker-compose. See the version here: https://github.com/docker/compose/releases

sudo curl -L \
  https://github.com/docker/compose/releases/download/1.29.1/docker-compose-Linux-x86_64 \
  -o /usr/loca/bin/docker-compose
chmod +x /usr/local/bin/docker-compose
docker-compose --version

# booting up the containers specified in the `mongo.yml`:
docker-compose -f mongo.yml up

# turn down:
docker-compose -f mongo.yml down

10. Dockerfile - Build your own Docker Image

(see also the notes “Building Images: The Dockerfile Basics”)

Dockerfile is a blueprint for creating a Docker image.

FROM node:13-alpine

ENV \
    MONGO_DB_USERNAME=admin \
    MONGO_DB_PWD=password

# RUN command to be executed when creating the image
RUN mkdir -p /home/app

# COPY executes in the host machine
COPY . /home/app

# CMD is the entrypoint command
# command, arg1
CMD ["node", "/home/app/server.js"]

The filename MUST be exactly Dockerfile (including the capital D).

Assuming you’re on the same directory of the Dockerfile:

docker image build -t my-app:1.0 .

# check if it really created the image:
docker image ls

11. Private Docker Repository

The full image name is registryDomain/imageName:tag. When the registryDomain is omitted, the default is Docker Hub.

Amazon ECR (Elastic Container Repository) is a service that provides private Docker repository.

# check which image you want to push to your repository
docker image ls

# docker login
# NOTE: AWS has a specific CLI command for it.
docker login ${registryDomain}

# tag the image
docker tag ${imageName}:${tag} ${registryDomain}/${imageName}:${tag}

# upload (push) the image
docker push ${registryDomain}/${imageName}:${tag}

# UPDATING AND PUSHING A NEW VERSION
####################################

# make the change you needed to do in the Dockerfile,
# and then build the new image:
docker image build -t my-app:1.1

# tag it
docker image tag my-app:1.1 ${registryDomain}/my-app:1.1

# push it
docker image push ${registryDomain}/my-app:1.1

12. Deploy docker application on a server

Docker compose yaml file:

version: '3'
services:
  my-app:
    image: MY-PRIVATE-REGISTRY-DOMAIN/my-app:1.0
    ports:
      - 3000:3000
  mongodb:
    image: mongo
    ports:
      - 27017:27017
    environment:
      - MONGO_INITDB_ROOT_USERNAME=admin
      - MONGO_INITDB_ROOT_PASSWORD=password
    mongo-express:
      image: mongo-express
      ports:
        - 8080:8081
      environment:
        - ME_CONFIG_MONGODB_ADMINUSERNAME=admin
        - ME_CONFIG_MONGODB_ADMINPASSWORD=password
        - ME_CONFIG_MONGODB_SERVER=mongodb

And then

docker-compose -f docker-compose.yaml

13. Docker Volumes - Persisting Data

A directory in physical host file system is mounted into the virtual file system of Docker.

3 Volumes Types:

Example of Named Volume being used in a docker-compose file:

version: '3'
services:
  mongodb:
    image: mongo
    ports:
      - 27017:27017
    volumes:
      - db-data:/var/lib/mysql/data

  mongo-express:
    image: mongo-express
    # ...

volumes:
  db-data # now you can reference this name in more than one container

14. Docker Volumes Demo

Using the project from this repo: https://gitlab.com/nanuchi/developing-with-docker

Check the docker-compose.yaml file. There’s a volumes: there, and it’s being used in volumes: of mongodb.

MacOS Tip: Docker in MacOS is actually a Linux virtual machine and then it’s the host of the containers. Here’s how to access the shell of such Linux virtual machine screen ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/tty

15. Create Docker Hosted Repository on Nexus

16. Deploy Nexus as Docker Container

# super user
sudo su

# install docker from snap
apt update
snap install docker

# create a docker volume for persistent data
docker volume create --name nexus-data

# check volumes
docker volume ls

# create and run the nexus container
docker container run \
  --detach \
  --publish 8081:8081 \
  --name nexus \
  --volume nexus-data:/nexus-data \
  sonatype/nexus3

# install net-tools for debugging
apt install net-tools

# check the open ports
netstat -lnpt