How To Install Docker and Run Containers on CentOS 7

About Docker

Docker is a program that performs os level virtualization, it can package an application and its dependencies in a virtual container that can run on any Linux server.

In this tutorial I will show you how to install Docker CE on Centos and basic concepts and commands.  I am starting this by assuming you have the root privileges on your system if you are a non-root user with sudo privileges add a prefix ‘sudo’ on all commands I given below.

 

Install Docker

First update your system packages:

#yum update

Install the required dependencies:

#yum install yum-utils device-mapper-persistent-data lvm2

Add docker stable repository to your system

#yum-config-manager –add-repo https://download.docker.com/linux/centos/docker-ce.repo

Install the latest version of Docker CE using the command:

#yum install docker-ce

After the installation start the Docker daemon and enable it to automatically start at boot time:

#systemctl start docker

#systemctl enable docker

Output will be something like below image:

If you want to know Docker version:

#docker -v

Docker version 18.06.1-ce, build e68fc7a

Now we have a working Docker installation, the syntax of Docker commands is:

#docker [option] [subcommand] [arguments]

You can list all available docker command by just typing:

#docker

Docker Image Downloading

A Docker image is an immutable binary file including the application and all other dependencies such as binaries, libraries and instructions necessary for running the application. In short a Docker image is a snapshot of a Docker container.

The Docker Hub is a cloud-based registry service which is used for keeping the Docker images. One can put a docker image either in a public or private repository.

You can search docker images using the command:

#docker search [os_name]

For example, If you want to search all available ubuntu images in docker you can use the below command:

#docker search ubuntu

Output screen shows the list of available ubuntu images:

If you want to download ubuntu, you can do that by using the image pull command

#docker image pull ubuntu

Output:

Depending on your Internet speed and the size of the image, download may take a few seconds or a few minutes.

Once the image is downloaded we can list the images with:

#docker image ls

Output screen seems like below:

If you want to delete an image you can do that with docker image rm [image_name] command:

For example:

#docker image rm ubuntu

The output shows:

Launching Docker Container

The docker run is the command used to launch Docker containers.

#docker run ubuntu

You can enter either image name or image ID here.

You can see the running containers using:

#docker ps

output:

The switch -it allows us to interact with the container via the command line.

#docker run -it ubuntu /bin/bash

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