Getting Started with Docker!

12:00 pm - 1:30 pm 1st june, 2024

Hi, I am Milind

8+ years in building large scale ecommerce.
Checkout, Payments, Promotions & Integrations
Java/Spring, PHP and JavaScript/Node.js
commercetools, Magento/Adobe Commerce, Shopify and Hybris/SAP Commerce.

Operating System

an interface between user and hardware
manages resources like memory, cpu, files and devices
networking, security and process management

Linux

Linux® is an open source operating system (OS).
Kernel: The base component of the OS.
System user space: The administrative layer for system-level tasks like configuration and software install. shell, daemons, processes and the desktop environment.
Applications: Apps include everything from desktop tools and programming languages to multiuser business suites.

Linux Kernel

Linux Container

Namespace

Control Group

A Linux® container is a set of 1 or more processes that are isolated from the rest of the system.

Linux kernel feature that partition kernel resources such that one set of processes sees one set of resources, while another set of processes sees a different set of resources.

It allows you to allocate resources such as CPU time, system memory, network bandwidth, etc, so that an activity per service instance can be ran and constrained by cgroups on the system.

Exercise 1

# CLI to List system namespaces.
lsns --help

# list all ns
lsns

Virtualization vs Containers ?

Docker

Docker is an open platform for developing, shipping, and running containerized applications.

Installing Docker

https://docs.docker.com/engine/install/ubuntu/

# 1. Set up Docker's apt repository.

# Add Docker's official GPG key:
sudo apt-get update
sudo apt-get install ca-certificates curl
sudo install -m 0755 -d /etc/apt/keyrings
sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc
sudo chmod a+r /etc/apt/keyrings/docker.asc

# Add the repository to Apt sources:
echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu \
  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update

# 2. Install the Docker packages.
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

# Docker Service Start
sudo service docker start

# Verify that the Docker Engine installation is successful by running the hello-world image.
sudo docker run hello-world

WSL 2

https://www.freecodecamp.org/news/how-to-install-wsl2-windows-subsystem-for-linux-2-on-windows-10/

https://learn.microsoft.com/en-us/windows/wsl/install

Exercise 2: Running a Docker Container

# download an docker image, eg nginx
docker pull nginx

# run image, use -d to run in background
docker run --name exercise2 -p 8080:80 nginx

# check in browser
http://localhost:8080/

# check docker running process
docker ps

# stop
docker stop exercise2

# restart
docker start exercise2

# check logs
docker logs exercise2

# Get PID for docker container
docker inspect --format '{{.State.Pid}}' exercise2

# List docker container ns
sudo ls -la /proc/7059/ns

Building a Docker Container: Dockerfile

A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image.

https://docs.docker.com/reference/dockerfile/

Exercise 3: Dockerize a Node.js API

# Build a docker container
docker build -t node-api -no-cache .

# Run a docker container
docker run -p 3000:3000 node-api

# Remove image
docker rmi node-api --force

# Clear cache!
docker system prune -a

# Dockerfile

FROM node:22-alpine

RUN mkdir -p /home/node/app/node_modules && chown -R node:node /home/node/app

WORKDIR /home/node/app

COPY package*.json ./

USER node

RUN npm install

COPY --chown=node:node . .

EXPOSE 3000

ENTRYPOINT [ "node", "index.js" ]

Docker Compose

Docker Compose is a tool for defining and running multi-container applications.

# compose.yaml

services:
  nginx:
    image: "nginx"
    ports:
      - "80:80"
      
  node:
  	image: "node"
    
  redis:
    image: "redis:alpine"