(Day 11) Task : Docker Architecture & Docker Installation :-

Docker Architecture :-

Docker has a client-server architecture, which means it has two main parts:

• The client that you use to type Docker commands.

• The server (Docker engine also called the Docker Daemon) that does all the work behind the scenes.

The main parts of Docker architecture :-

1. Docker Client :

• The interface we (the user) interact with.

• Sends commands to the Docker Daemon.

• Acts like a remote control.

  • Examples of commands:

      docker search <image-name>
      docker pull <image-name>
    

2. Docker Daemon (Docker Engine) :

• The brain behind Docker.

• Listens to Docker Client requests.

• Builds, runs, and manages containers.

• Runs on the host OS.

• Can communicate with other Docker Daemons.

3. Docker Images :

• Read-only templates used to create containers.

• it’s a single file which contains all dependencies needed to run any program(code, libraries).

• We can think of it as a recipe.

  • Ways to create a Docker image :

    • Using a Dockerfile :

      • You write a Dockerfile with instructions to build an image.

      • Then run docker build to create the image.

4. Docker Containers :

• The running instances of Docker images.

• Lightweight and portable.

• Each container runs in isolation.

• Think of it like a "live" app created from an image.

• Note :- Image becomes container when run on Docker Engine.

5. Dockerfile :

• A text file with a list of instructions to create a Docker Image.

• Like a blueprint or recipe to make an image.

• Example line: FROM ubuntu, COPY . /app, RUN npm install.

6. Docker Registry (Docker Hub):

• A storage for Docker Images just like GitHub.

• Public example: Docker Hub.

• You can push images to it or pull images from it.

  • Two types Of Registries :-

    • Public Registry :

      • Open to everyone; anyone can pull or push images (depending on access).

      • Most popular example: Docker Hub.

      • Other public registries: GitHub Container Registry, Quay.io, etc.

    • Private Registry :

      • Restricted access; only authorized users can push/pull images.

      • Often used by companies for internal or sensitive images.

      • Can be self-hosted or cloud-based.

Docker Workflow :-

• Create a Dockerfile: Developer writes a Dockerfile .

  Dockerfile is like a recipe for building a Docker image. It contains all dependencies & Required Softwares.

• Docker file Executes on Docker Engine/Daemon and gives image and these images are stored in Docker Hub or Registry.

• Execution of image makes Container .

Installing Docker :-

sudo yum install docker -y

To See all Images Present in Your Local machine :

•   docker images
  

To Find Out Images in Docker Hub :

•   docker search <image_name>
  

To Find Image from Docker hub to Local Machine :

•   docker pull <image_name>
  

To Create and Start a container & we’ll reach inside Container :

•   docker run -it --name <name-u-wanna-give> <image-name>
  

To Check service is Start or Not :

•   service docker status
    # Or 
    docker info
  

To Start a Container & go inside Container :

•   docker start <container_name>             # To Start Container
    docker attach <container_name>            # To Go inside Container
  

To See all containers & running Containers:

•   docker ps -a                         # ps --> process Status While -a is all containers
    docker ps
  

To Stop Container :

•   docker stop <container_name>
  

To Delete Container :

•   docker rm <container_name>
  

To Stop & exit Container :

•   exit