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.
First update your system packages:
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 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 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 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
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:
docker image rm ubuntu
The output sows:
Launching Docker Container
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:
-it allows us to interact with the container via the command line.
docker run -it ubuntu /bin/bash