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Docker by Hitesh(Youtube)

What is Docker and its usage?

Docker is an open platform for developing, shipping, and running applications. Docker provides the ability to package and run an application in a loosely isolated environment called a container. The isolation and security lets you run many containers simultaneously on a given host. Containers are lightweight and contain everything needed to run the application, so you don't need to rely on what's installed on the host. You can share containers while you work, and be sure that everyone you share with gets the same container that works in the same way.

What can I use Docker for?

Docker Architecture

Architecture

Docker uses a client-server architecture. The Docker client talks to the Docker daemon, which does the heavy lifting of building, running, and distributing your Docker containers. The Docker client and daemon can run on the same system, or you can connect a Docker client to a remote Docker daemon. The Docker client and daemon communicate using a REST API, over UNIX sockets or a network interface. Another Docker client is Docker Compose, that lets you work with applications consisting of a set of containers.

What is image and container

Think of image as like software and your PC or laptop is the container that runs that software. Similarly you build containers to run that image and that container runs on the docker engine. Virtual Machine (VM) runs whole of the operating system over the OS but containers actually contains the software and bare minimum of whatever configuration is required of OS.

Some useful Commands

Pulling an image

`docker pull <image-name>

View all downloaded images

docker image ls

Running a docker image

docker run --name <container-name> <image-name> some other arguments that you can pass

  1. docker run --name <container-name> -d <image-name> : this runs the container in detached mode, meaning your terminal won't be used to display output and the container will run in background.
  2. docker run <image-name>:<version to run a specific version of the image
  3. docker run --network <network-name> to run a container on specific network

Running a existing container

docker start <container-name/container-tag>

Stopping a running container

docker stop <container-name/container-tag> or docker container stop <container-name/container-tag>

Viewing Containers

  1. Running containers: docker ps or docker container ls
  2. All containers: docker ps -a

Remove all stoped Containers

docker container prune

See Containers log

docker logs <container-name/container-id>

Write docker commands in multiple line in terminal

docker run --name test \
-p 8081:8081 \
-e ...

Docker Compose

services:
    <container-name-1>:
        image: <image-name-1>
        ports:
            - "<host-port>:<container-port>"
        environment:
            - <environment-key>=<environment-value>
        volumes:
            - mymongo-data:/data/db
    <container-name-2>:
        image: <image-name-2>
        restart: always       %% makes sure to restart container if it exits %%
        ports:
            - "<host-port>:<container-port>"
volumes:
    mymongo-data:
        driver: local

Note: All the containers in a docker-compose.yml file share the same network

Run docker-compose

docker-compose -f docker-compose.yml up

Close all the containers in docker-compose

docker-compose -f docker-compose.yml down

Dockerfile (Creating an Image)

  1. Create the dockerfile in the root dir.

  2. Given a example of a flask image

    FROM python:3-alpine3.15

WORKDIR /app

COPY . /app

RUN pip install -r requirements.txt

EXPOSE 3000

CMD python ./index.py

Build docker image using dockerfile

docker build -t <username>/<image-name>:<version> <Dockerfile-path>

Run the image built using dockerfile

docker container run -d -p 3000:3000 <username>/<image-name>:<version>

Push image to docker hub

docker push <username>/<image-name>:<version>