Docker Basics

When Do You Need to Use Docker?

• For replicating the environment on your server, while running your code locally on your laptop
• Experimenting with new things on your laptop without breaking the repositories.
• Creating a production grade environment on you PC with just simple steps.
• For instant testing of your application.
• For Docker CI/CD during numerous development phases (dev/test/QA)
• For distributing your app’s OS with a team, and as a version control system.

Simple ways to setup docker: -

Route 1 (curl required):

# curl https://get.docker.com | sh

Route 2:

#apt-get update

#apt-get install \

    apt-transport-https \

    ca-certificates \

    curl \

    software-properties-common

#curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add –

#apt-key fingerprint 0EBFCD88

#add-apt-repository \

   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \

   $(lsb_release -cs) \

   stable"

#apt-get update

#apt-get -y install docker-ce

#docker run hello-world

(Note: Use root to execute Docker commands if you haven’t added your user to the docker group

If you want to add your user to docker group then:

$ sudo usermod -aG docker $USER

After this root access will not be required)

How to use Docker?

• For checking the number of images on your system, use the following command –

$ docker images

• For searching an image in the Docker Hub –

$ docker search <image>

• docker pull – Pulls an image or a repository from a registry

$ docker pull ubuntu

(Note: By default the tag will be “latest” otherwise you need to specify)

• docker ps – To see the running or stopped docker containers

$ docker ps -a

• docker run – Creates and starts a new container according to the supplied attributes.

$ docker run  --name containerName –p 8080:80 –it  Ubuntu /bin/bash

(Note: 8080 refers to the host port and 80 refers to the container port.

Refer to https://docs.docker.com/engine/reference/run/ for attribute details and more options)

• docker attach – It will attach the host terminal to the container terminal

$ docker attach containerName

(Note: exit command inside the container will stop the container and return to the host terminal session but if you want to keep the container running then

Ctrl + (p and q)

• docker start – Starts one or more stopped containers

$ docker start containerName/Container ID

• docker stop – Stops one or more running containers

$ docker stop containerName/Container ID

• docker build – Builds an image form a Docker file

• docker login – Helps to login to your docker account and then you can push or pull your private or public Docker images.

• docker push – Pushes an image or a repository to a registry

• docker export – Exports a container’s filesystem as a tar archive

• docker exec – Runs a command in a run-time container

• docker commit – Creates a new image from a container’s changes

How to create your own Docker Image?

·       Create your account on Docker repo site : hub.docker.com

·       Create a Repository with some initial description.

·       User docker commit to save your running container in your local repo.

$ docker commit -m "Apache web server" -a "PrashPlus" 8931afa5aaa6 apacheserver:latest

·       Tag your image with the docker Id and your repository name.

$ docker images

Find your committed image

$ docker tag bb38976d03cf yourhubusername/apacheserver:latest

·       docker push yourhubusername/apacheserver

·       Now your required PC run docker pull and you are ready to go.

$ docker pull yourhubusername/apacheserver

(Feel free to ask for additional commands or any changes required.)