Docker

 [root@ip-172-31-6-122 ~]# history

    1  yum update

    2  yum install docker

    3  systemctl start docker

    4  docker ps

    5  systemctl status docker

    6  docker run -d nginx

    7  docker ps

    8  docker run -d --name myweb nginx

    9  docker ps

   10  docker container ls

   11  docker  images

   12  docker pull httpd

   13  docker images

   14  docker ps

   15  history

Docker is a set of platforms as a service (PaaS) products that use the Operating system level visualization to deliver software in packages called containers. Containers are isolated from one another and bundle their own software, libraries, and configuration files; they can communicate with each other through well-defined channels

 

Docker V/S VM:

 

Docker Architecture:

 

 

 

Docker Engine

It is the core part of the whole Docker system. Docker Engine is an application which follows client-server architecture. It is installed on the host machine. There are three components in the Docker Engine:

• Server: It is the docker daemon called dockerd. It can create and manage docker images. Containers, networks, etc.
• Rest API: It is used to instruct docker daemon what to do.
• Command Line Interface (CLI): It is a client which is used to enter docker commands.

 

Docker Client

Docker users can interact with Docker through a client. When any docker commands runs, the client sends them to dockerd daemon, which carries them out. Docker API is used by Docker commands. Docker client can communicate with more than one daemon.

Docker Registries

It is the location where the Docker images are stored. It can be a public docker registry or a private docker registry. Docker Hub is the default place of docker images, its stores’ public registry. You can also create and run your own private registry.

When you execute docker pull or docker run commands, the required docker image is pulled from the configured registry. When you execute docker push command, the docker image is stored on the configured registry.

Docker Objects

When you are working with Docker, you use images, containers, volumes, networks; all these are Docker objects.

Images

Docker images are read-only templates with instructions to create a docker container. Docker image can be pulled from a Docker hub and used as it is, or you can add additional instructions to the base image and create a new and modified docker image. You can create your own docker images also using a dockerfile. Create a dockerfile with all the instructions to create a container and run it; it will create your custom docker image.

Docker image has a base layer which is read-only, and the top layer can be written. When you edit a dockerfile and rebuild it, only the modified part is rebuilt in the top layer.

Containers

After you run a docker image, it creates a docker container. All the applications and their environment run inside this container. You can use Docker API or CLI to start, stop, delete a docker container.

Below is a sample command to run a ubuntu docker container:

docker run -i -t ubuntu /bin/bash

Volumes

The persisting data generated by docker and used by Docker containers are stored in Volumes. They are completely managed by docker through docker CLI or Docker API. Volumes work on both Windows and Linux containers. Rather than persisting data in a container’s writable layer, it is always a good option to use volumes for it. Volume’s content exists outside the lifecycle of a container, so using volume does not increase the size of a container.

You can use -v or –mount flag to start a container with a volume. In this sample command, you are using geekvolume volume with geekflare container.

docker run -d --name geekflare  -v geekvolume:/app nginx:latest

Networks

Docker networking is a passage through which all the isolated container communicate. There are mainly five network drivers in docker:

1. Bridge: It is the default network driver for a container. You use this network when your application is running on standalone containers, i.e. multiple containers communicating with same docker host.
2. Host: This driver removes the network isolation between docker containers and docker host. It is used when you don’t need any network isolation between host and container.
3. Overlay: This network enables swarm services to communicate with each other. It is used when the containers are running on different Docker hosts or when swarm services are formed by multiple applications.
4. None: This driver disables all the networking.
5. macvlan: This driver assigns mac address to containers to make them look like physical devices. The traffic is routed between containers through their mac addresses. This network is used when you want the containers to look like a physical device, for example, while migrating a VM setup

 

 

Install Docker:

Create EC2 instance:

Login on ec2 instance as a root.

Execute below command:

#yum update -y

#yum install docker

#systemctl start docker

#systemctl status docker