Getting Started With Docker - Quick Start Guide

Getting Started With Docker - Quick Start Guide

Docker Engine

• Platform as a Service (PaaS)
  • Cloud platform service. Allows you to manage its application and data. Cloud service provider manages servers, storage, networking, and computing power.
• Provides OS level virtualization platform
  • The OS kernel allows multiple isolated instances.

Components of the Docker Engine

1. Docker Daemon:
   • Brain of the Docker
   • Persistent background process ( such as our normal system service, which runs continuously.)
   • Process named “dockerd” listens for Docker API requests and manages Docker objects. (create docker images, run docker containers, route traffic among Docker containers.
   • Manages Docker Objects.
     • Docker images
     • Docker Containers
     • Docker Networking
     • Docker Volumes
2. Docker Engine REST API:
   • Docker API used to keep interaction with Docker Daemon.
   • Communication performed using HTTP requests.
   • Application Programming Interface (API)
   • This API communicate using UNIX Socket (unix:///var/run/docker.sock)
3. Docker CLI
   • Command Line Interface.
   • This user interface allows the user to manage Docker objects and communicate to Docker daemon.

Docker Engine - Birds Eye View

Docker Architecture

• Docker architecture consist of 3 main components
  • Docker Client
  • Docker Host
  • Docker Registry

1. Docker Client - This is where we are doing stuff

• Enables us to interact with Docker daemon
• Docker Clients typically reside on the same host where Docker daemon is running. But in some cases, it can run on a remote host as well.
• Docker client provides us to command line interface to issue command to Docker daemon (docker build, docker run.. )

2. Docker Host

• Provides a complete infrastructure to execute and run applications
• Main control center
• Docker daemon pulls images from docker registry and build container images and run application as we requested by Docker CLI/ Docker Client

3. Docker Objects

There are numerous objects available. One or more objects required to run an application in a container.

• Images
• Containers
• Networking
• Storage

3.1. Docker Images

• Each of the files in a Docker image consist it’s own layer.
• Use to build containers
• Use to store and ship containers
• Read only binaries snapshot or template
• Consist of File system and required libraries to run a specific application environment
• Shareable using public / private registry
• Consists a series of layers and each command composed to a read-only layer.

3.2. Docker Containers

• Encapsulated environments which can run applications
• Running instance of a Docker image

3.3. Docker Networking

• Bridge network
• Overlay network
• Macvlan network
• Null

3.4. Docker Storage

• Data Volume
  • Support persistent data storage. (data will not loss even after the container restart/delete)
  • Data volumes resides on the host file system
  • Container data can accessible from host-file system
  • Scenarios - Running state full applications
• Data Volume Container
  • This volume type can share among multiple containers
  • This is independent from application container - shared volumes
  • Scenarios - sharing same configuration among multiple containers
• Directory Mount
  • Directly mount the host’s local directory into a container.
  • Any directory on the host can be mounted as a source for the container volumes.
  • Scenarios - mounting hosts .ssh folder, .bash_profile file, .kubectl folder into container to share the same host configuration to the container.
• Storage Plugins
  • Allows to connect other storage types such as data LUNs, SAN storages, NFS, SAMBA
  • There are number of storage plugins available
  • Azure File Storage, EMC

4. Docker Registry

• This is where docker images can store
• There may be private and public registries

Creating a Dockerfile

Sample Dockerfile

#Download base image ubuntu 20.04
FROM ubuntu:latest
USER root
# labels about the custom image
LABEL maintainer="NGINX Sample WebServer"
LABEL maintainer="dimuit86@gmail.com"
LABEL description="This is custom Docker Image for \
DigitalAvenue DevOps."

# Update the image to the latest packages \
# Install Nginx
RUN apt-get update -y && \
    apt-get install nginx -y && \
    rm -rf /var/lib/apt/lists/* && \
    apt clean

RUN rm -rf /var/www/html/*.html

COPY ./index.html /var/www/html/index.html

# Volume configuration
VOLUME ["/var/log/nginx", "/var/www/html"]

# Expose Port for the Application 
EXPOSE 80 443

# Last is the actual command to start up NGINX within our Container
CMD ["nginx", "-g", "daemon off;"]

Dockerfile Definitions

• FROM : parent image/ base image use to create a container with a specific application
• LABEL : Define a description, ownership, authority
• RUN : Specific command to make changes to base image.
  • Install new applications, packages, libraries
  • Adding new users
  • Changing file permissions and ownership
• USER : Defines the username that all the commands will be run as the mentioned user.
• WORKDIR : Defines default working directory where all the commands are going to be executed. WORKDIR comes before “ENTRYPOINT” OR “CMD”
• CMD : This command runs when the container starts
• ENTRYPOINT : This is where the default application is going to start when the container is created.

Practical 01: Containerize NGINX Web Application

In this demonstration, we are going to spin up a simple Nginx website using Docker Ubuntu base image. And we’ll copy custom “nginx.conf” configuration files and “index.html” files into the docker container.

STEP 01: Create a “index.html”

<!doctype html>
<html>
<head>
    <meta charset="utf-8">
    <title>Hello, Nginx!</title>
</head>
<body>
    <h1>Hello, Digital Avenue!</h1>
    <p>We have just configured our Nginx web server on Ubuntu Server!</p>
</body>
</html>

STEP 02: Create Custom “nginx.conf” file

user www-data;
worker_processes auto;
pid /run/nginx.pid;
include /etc/nginx/modules-enabled/*.conf;
events {
        worker_connections 768;
}
http {
        sendfile on;
        tcp_nopush on;
        tcp_nodelay on;
        keepalive_timeout 65;
        types_hash_max_size 2048;
        include /etc/nginx/mime.types;
        default_type application/octet-stream;
        ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3; # Dropping SSLv3, ref: POODLE
        ssl_prefer_server_ciphers on;
        access_log /var/log/nginx/access.log;
        error_log /var/log/nginx/error.log;
        gzip on;
        include /etc/nginx/conf.d/*.conf;
        include /etc/nginx/sites-enabled/*;
}

STEP 03: Create a Dockerfile

#Download base image ubuntu 20.04
FROM ubuntu:latest

# labels about the custom image
LABEL maintainer="NGINX Sample WebServer"
LABEL maintainer="dimuit86@gmail.com"
LABEL description="This is custom Docker Image for \
DigitalAvenue DevOps."

# Update the image to the latest packages \
# Install Nginx
RUN apt-get update -y && \
    apt-get install nginx -y && \
    rm -rf /var/lib/apt/lists/* && \
    apt clean

RUN rm -rf /etc/nginx/nginx.conf
RUN rm -rf /var/www/html/*.html

COPY ./nginx.conf /etc/nginx/nginx.conf
COPY ./index.html /var/www/html/index.html

# Volume configuration
VOLUME ["/var/log/nginx", "/var/www/html"]

# Expose Port for the Application 
EXPOSE 80 443

# Last is the actual command to start up NGINX within our Container
CMD ["nginx", "-g", "daemon off;"]

docker build -t nginx-web:v1 .

docker run -d -p 8080:80 –name nginx-web nginx-web:v1

http://localhost:8080

Build a Docker Image:

docker build -t : .

Run Docker Container

docker run -d -p 8080:80 –name :

Inspect Docker Container

docker container ls

docker container <CONTAINER-NAME/ID>

Log into Docker Container

docker run -it <CONTAINER-NAME/ID>

Accessing Docker Volumes:

Docker Volume Location:

Linux : /var/lib/docker/volumes/

Windows WSL: Windows Subsystem for Linux (WSL2)

Ctrl + R = “\wsl$\docker-desktop-data\version-pack-data\community\docker\volumes”

Practical 02: Containerized Node Application - Multi Stage Docker Images

# ================================================================
#             B U I L D E R     S T A G E
# ================================================================
FROM node:14-alpine AS builder

LABEL Name="Node.js Demo App - MULTI STAGE"
LABEL maintainer="dimuit86@gmail.com"
LABEL description="This is custom Docker Image for \
DigitalAvenue DevOps."

ENV NODE_ENV production

# Create app directory
WORKDIR /usr/src/app

WORKDIR /app

# Copy package.json and .lock file 
# from  host to docker container
COPY package.json package-lock.json ./

# Installing dependencies
# RUN npm install

# For Production usage
RUN npm ci --only=production

# Bundle app source
COPY . .

# ================================================================
#            D E P L O Y     S T A G E
# ================================================================
FROM nginx:1.19-alpine AS server
# Copy custom nginx.con file
COPY ./nginx.conf /etc/nginx/conf.d/default.conf

# Copy build output from build stage
COPY --from=builder /usr/src/app /usr/share/nginx/html

# Open port 80
EXPOSE 80

# Start nginx from backgrood
CMD ["nginx", "-g", "daemon off;"]

docker build -t nodejs-web:v1 .