Overview of Docker

Introduction:

This article is to provide the overview of docker.

Requirements:

• A linux machine

• "docker" to be installed on linux machine

Tasks:

• Provision a linux (cent os) machine (in aws/azure/google cloud or setup a linux machine on Oracle Virtual box) and install docker on the top of linux machine: yum install docker -y
• Start and enable docker service: systemctl start dockersystemctl enable docker
• Then download the docker image with below command: docker pull image_name:version

• To check the images downloaded by docker, use the below command: docker images

• Check if any container is running with below command: docker ps -a

• Download the container image with below command: docker pull imagename:version

• The detail of the docker images can be found in https://hub.docker.com/ portal
• Now run the below command to run the docker: docker run -it image_name:version

• It will straight away take you inside the container
• To avoid it, run the below command to start the container in detached mode which will start the container in background: docker run -dit image_name:version

• To give a name to the newly launched container, the below command is used: docker run -dit --name name_of_container image:version

• Access/login into the container with below command: docker attach "container_id" or "container_name"

• To exit from the container, "exit" command can be used which shut down the container

• To come out of the command, press ctrl+p+q. It will not shutdown the container

• To stop the container, use the below command: docker stop container_id or container_name

• To create a personalized docker image from a configured container, use the below command: docker commit container_name new_image_name:version

• Now run a container from this personalized image with the same command which was used earlier:

• The "docker commit" command is being used to provision the containers manually.
• It might be a query about why should we create a personalized container when the docker images are already available. The answer is all packages (like net-tools, python etc.) are not pre-installed in the docker image. That need to be configured manually. But this process can be automated with Dockerfile.
• Create a directory and create a Dockerfile inside it. Please find the sample dockerfile and its format below: From base_image:versionRUN command............

• Next, run the below command to build the image: docker build -t personalized_image_name:version directory_location_of_docker_file