What is Docker?

Docker is an open source project that makes it easier to create containers and container-based apps. Docker is also used to organize dependencies based on the project, so a user doesn't need to have random and unused dependencies on their system.

Why we use Docker?

Docker also has an amazing community that has built many containers already for different programs, so it removes the need of reinventing the wheel.

How to use Docker?

From https://www.scalyr.com/blog/create-docker-image/

Step 1: Create a Base Container

The Docker create command will create a new container for us from the command line:

docker - create --name nginx_base -p 80:80 nginx:alpine

If you don’t have the nginx:alpine image in your local docker image repository, it will download automatically. When this happens, you will see something like this:

Step 2: Inspect Images

Run the command:

docker images

If you look at the list of images on your system, you will now see the nginx:alpine image.

Step 3: Inspect Containers

Run the command:

docker ps -a

Note here that the container is not running, so you won’t see it in the container list unless you use the -a flag (-a is for all).

Step 4: Start the Container

Now we start the nginx container

docker start nginx_base

If you visit http://localhost. You should now see your nginx container.

Step 5: Modify the Running Container

So if you wanted to modify this running container so that it behaves in a specific way, there are a variety of ways to do that.

In order to keep things as simple as possible, we are just going to copy a new index.html file onto the server. You could do practically anything you wanted here.

Let’s create a new index.html file and copy it onto the running container. Using an editor on your machine, create an index.html file in the same directory that you have been running Docker commands from.

Then save the file and return to the command line. We will use the docker cp command to copy this file onto the running container.

docker cp index.html nginx_base:/usr/share/nginx/html/index.html

Now reload your browser or revisit http://localhost. You will see the edits made in your index.html file.