Docker (Part - 1) : Introduction and Basic Commands

What is Docker, Docker container and Docker Image?

Docker is a containerization platform that allows developers to package applications and their dependencies into isolated units called containers.

A Docker container is a lightweight, standalone, executable package of software that includes everything needed to run an application: code, runtime, system tools, system libraries and settings.

A Docker image is a read-only template that defines the contents of a Docker container. It includes the application code, runtime, system tools, system libraries, and settings. It is mainly used to create a docker container.

Docker vs. Virtual Machine

Docker and virtual machines (VMs) are both technologies that can be used to run applications in isolated environments. However, they have different approaches and use cases.

Docker is a containerization platform that allows developers to package applications and their dependencies into isolated units called containers. Containers share the underlying operating system of the host machine, but they are isolated from each other and the host operating system.

Virtual machines are hypervisor-based virtualization platforms that allow multiple operating systems to run on the same physical machine. Each virtual machine has its own operating system, CPU, memory, and storage.

Docker Hub

In this section, we will try to Understand Docker Hub. But first, we need to install docker on our local machine. Here is the installation guide.
https://docs.docker.com/engine/install/

After installing docker we can now check the version on our docker engine.

docker -v

Now we will pull a docker image from the docker hub later we will create our docker images. Docker Hub is a cloud-based platform provided by Docker that serves as a registry for Docker images. It allows developers to store, share, and manage Docker container images, which are the packaged applications and their dependencies that can be used to create Docker containers.

We need to create an account in the docker hub.

We will use Redis images from the docker hub. https://hub.docker.com/_/redis. but you can choose whatever images you want to play with.

Docker Basic Commands

We have installed the docker and have basic knowledge about the docker hub. We will use Redis from Docker Hub but you are free to choose any docker image you want.

Pull Docker Image

Now we will pull the image from the docker hub.

docker pull redis

Check All Images

Now we have the docker image for Redis from the docker hub. We can check all available docker images

docker images

Run Image

Let's create a docker container for our Redis image by running the image.

docker run redis

Check All Running Containers

In a new terminal, We can also check all running containers.

docker ps

We can see the container ID and port along with other information. We can stop our running container by control + c

Run Docker Images on Detach Mode

We can also run docker images in detach mode.

docker run -d redis

It will only give the container ID in return but our docker image is running.

Stop Docker Container

We need the container_id to stop a Docker which is running on detach mode.

docker stop container_id

Check All Docker Container

After stopping a container, If we need to start it again we need the container id. To check all container id regardless it is running or not.

docker ps -a

Now we have our container ID.

Start Previous Running Container

We will be able to start the container by id or name

docker start container_id/container_name

Binding a container port to the host

By running an image, We are creating a container. Which has a port number but that is not our local machine port. That is the container port. So we need to bind the container port with our local port.

docker run -d -p local_port:container_port redis

in example

docker run -d -p 3000:8080 redis

Here, we are binding our local port 3000 with the container port 8080. So our container port will be 8080 which will be accessible by. our local port 3000.

By using port binding we will be able to run as much as containers from the same Redis image just by defining different port numbers.

Set Custom Name For Container

If you check, you will find every docker container has a random name. If you want set a name for your container

docker run -d -p 3000:8080 --name redis-demo redis

Now our container name is redis-demo . We can use it instead of the docker container ID.

We can stop the container by using the container name

docker stop redis-demo

Also, start the container

docker start redis-demo

Check Docker log

To check everything about our container we can check the log of that container

docker logs container_id/container_name

Get The Interactive Terminal For Container

To check a running container or interact with it

docker exec -it container_id/container_name /bin/bash

Create Docker Network

Docker networks allow containers to communicate with each other and with the outside world. By default, containers are connected to a bridge network, which provides them with access to the host machine's network. However, you can also create custom networks to control how containers communicate.

docker network create mongo-network

Check Network List

docker network ls