Basic of Docker
Docker is a container management service.
The keywords of Docker are develop, ship and run anywhere.
The whole idea of Docker is for developers to easily develop applications, ship them into containers which can then be deployed anywhere.
Table of contents:
Features of Docker
Docker has the ability to reduce the size of development by providing a smaller footprint of the operating system via containers.
With containers, it becomes easier for teams across different units, such as development, QA and Operations to work seamlessly across applications.
You can deploy Docker containers anywhere, on any physical and virtual machines and even on the cloud.
Since Docker containers are pretty lightweight, they are easily scalable.
Why Virtualization ??
- Hardware Utilization
- To reduce number of physical servers
- Reduce Cost
- More different OS. Your whole design of virtualization is to target the Applications.
Installation
Before installing Docker, Linux kernal version should be 3.10 Check with below command:
uname -r
To install docker on RHEL/Centos/Ubuntu:
RHEL & Centos
sudo yum install docker
Ubuntu
sudo apt-get install docker
Verify the version with below command:
docker --version
Once docker get install check the docker service status with below command:
sudo systemctl status docker
To start the docker service
sudo systemctl start docker
To enable the docker service
sudo systemctl enable docker
With the docker installation dockerroot group get created where we have to add the userId to dockerroot group.
sudo usermod -aG dockerroot $USER
Docker Architecture
To learn about docker architecture refer below link:
https://docs.docker.com/get-started/overview/#docker-architecture
Let’s see do we have any images
sudo docker images
So where do I get images from ??
https://hub.docker.com/ {ex- nexus, jenkins, tomcat and centos}
Docker pull is a command that helps to download image or dependency from registry on to docker host
docker pull <image_name>
By default pull command will download latest copy of image. To download the specific version of an image
docker pull image_name:tag_info
I want to see how many containers are running ??
sudo docker ps
How to create container?? Let's see:
To create and run the container
docker run -it <image_name or image id > <controller_shell>
(controller shell= /bin/bash or /bin/sh)
Below are optional commands for container
docker run -it { attached mode runs in foreground }
docker run -dt { detached mode runs in background }
To start and stop container
sudo docker star <container_id>
sudo docker stop <conatiner_id>
To enter into running container
docker exec -it <container-id> bash
To start and login into the container which is in exit mode
docker start -ai <container_id>
Naming container
sudo docker run --name <CName> <docker_image> /bin/bash
sudo docker rename <old_CName> <new_CName>
sudo docker ps
exit
How to delete container
To delete a container it should be EXITED
sudo docker rm <cid>
or
sudo docker rm <cid> --force