Following series of commands will install Docker ( Docker CE ) In Ubuntu 16.04 or higher

1. Update apt

sudo apt-get update

2. Install prerequisites

sudo apt-get install \
    apt-transport-https \
    ca-certificates \
    curl \
    software-properties-common

3. Add Docker’s GPG key

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

4. Add Docker stable repository

sudo add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
   $(lsb_release -cs) \
   stable"

5. Update apt

sudo apt-get update

6. Install Docker CE

sudo apt-get install docker-ce

Now you have installed docker successfully in your Ubuntu 16.04 or higher. The following step helps you to verify your installation

Verifying Docker Installation

sudo docker run hello-world

The above command pulls and runs the hello-world test Docker image. If everything successful you should see the following output on your console.

$ sudo docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
1b930d010525: Pull complete 
Digest: sha256:c3b4ada4687bbaa170745b3e4dd8ac3f194ca95b2d0518b417fb47e5879d9b5f
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (amd64)
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/