Can you explain what a Dockerfile is and how it is used to create containers?

A Dockerfile is a text file containing a set of instructions that describe how to build a Docker image. It includes a sequence of commands that Docker executes to create a container image.

Main points:

• The Dockerfile specifies the base image, copying files, installing dependencies, running commands, and configuring the environment.
• Using the Dockerfile, the docker build command creates an image that can be run as a container.

Example of a simple Dockerfile for a Java application:

FROM openjdk:11
COPY ./app.jar /app/app.jar
CMD ["java", "-jar", "/app/app.jar"]

This file uses the OpenJDK 11 base image, copies the application file into the container, and sets the command to run the application.