What is a Dockerfile? Dockerfile Examples and How it is used?

by StarAgile

May 30, 2021
Category DevOps


WHAT IS A Dockerfile?

What Is a Dockerfile and How Will You Use It:

One of the main advantages of using containers is creating a consistent framework for development, testing, processing, and producing. Containers make the whole system portable; they also remove environment-specific issues.

To assist in creating a consistent container, you'll need an image designed in versioned and executable code. The Dockerfile is used to do this.

Dockerfile

Source

What Is A Dockerfile?

A Dockerfile is nothing more than a text file containing a few keywords and norms that Docker uses to generate an image. This image is then used to construct a container or a set of containers, all of which have the same configuration.

Why Dockerfile Is Used:

A friendly whale symbolizes docker in its logo, is an open-source platform that enables the deployment of applications within software containers. Its basic functionality is supported by the Linux kernel's resource isolation features, but it adds an easy-to-use API on top of them.

Docker is renowned due to the software delivery and installation opportunities. Containers help to resolve several common issues and inefficiencies. The DevOps Online Certification qualifies you to work in a team comprised of cross-functional team members.

1. Convenience of usage

A significant part of Docker's popularity results from its ease of use. Docker is easy to learn through Online DevOps Training, owing to the plethora of resources available for learning how to build and manage containers. Docker is an open-source project, which means that all you have to get started is a system with an operating platform that facilitates Virtualbox, Docker for Mac/Windows, or natively supports containers like Linux.

2. Faster system scaling

Containers allow more testing to be performed with significantly less computing hardware. Purchasing or leasing additional servers was the only way to scale a website in the early days of the Internet. Containers enable data center operators to process far more workloads with less hardware. Shared hardware results in cost savings. Operators have the option to keep their profits or passing the savings on to their customers.

3. Better Delivery of Software

Additionally, software delivery via containers can be more effective. Containers are easily transportable. Additionally, they are entirely self-contained. Containers have an isolated volume of disc. This volume goes to the container as it is built and implemented in different environments. The container ships with all of the program dependencies (libraries, runtimes, and so on). Containers can minimize the common configuration variance problems in binary or raw code deployment.

4. Flexibilities

Containerized systems have greater flexibility and adaptability than non-containerized applications. Container orchestrators are very effective tools for massive deployments and complex systems management. Container orchestrators manage thousands of containers and track them.

5. Software-Defined Networking

Docker is a networking container that facilitates software-defined networking. Operators can set isolated container networking without touching a single router through the Docker CLI and Engine. Developers and operators can build systems in configuration files using complex network topology and define networks. This is also a security advantage. Containers within an application may be isolated in a virtual network with tightly regulated ingress and egress routes.

6. The Development of Microservices Architecture

The increase in microservices has also led to Docker's popularity. Microservices are accessible functions that are typically accessed via HTTP/HTTPS.

Software systems usually start as "monoliths," that have several different system functions in a single binary. Monoliths can be challenging to manage and deploy as they develop. Microservices disintegrate a system into smaller, self-contained tasks that can be implemented independently. Containers make excellent microservice hosts. They are self-contained, easy to deploy, and highly effective.

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Best Practices to Write Dockerfile:

1. Recognize Cacheable Units

The use of multiple RUN commands to install packages can affect building process performance and productivity. Using a RUN Command prompt to implement all dependency packages helps to build a cacheable unit without multiple.

2. Image Size Should Be Reduced

Eliminate Unnecessary Dependencies – 

Do not install unnecessary tools like debugging tools in your image. If the package manager is used to install some recommended packages, use the package manager flags automatically to avoid installing unnecessary dependencies.

It simplifies the process of sharing, documenting, and reusing independent components within projects. Utilize it to optimize code reuse, maintain a consistent template, work as a team, accelerate delivery, and build scalable applications.

3. Maintenance of the image

  • Utilize the Docker Official Image

The use of the official Docker image removes the burden of repetitive dependencies and enlarges the image. There are three primary benefits of using the official image:

  1. This enables us to use an image based on best practices.
  2. The image's dependability and maintenance.
  3. Increased trust and security.
  • Make Use of Specific Tags

It is preferred to use a unique tag when selecting the base image. Do not use the latest image tag. The latest tag can undergo significant changes over time.

  • Use Minimal Flavors

The use of minimal image flavors reduces the image footprint. This enables applications to be deployed more quickly and safely.

4. Reproductivity

  • Build in a consistent environment from the source

For consistency, it is preferable to build an application with Docker in a controlled environment. We must stop building applications and apply them to the local registry.

  • Remove Build Dependencies by using Multi Staged Builds.

Multi-stage deployment is the preferred method for deploying applications.

We can create the application using a specific build image that includes all development dependencies and then transfers the compiled binaries to a particular Container image for running.

Dockerfile Examples:

You can directly access the file at this URL: 

GitHub Dockerfile

Please browse the file; it's sufficient for now to note the main structural elements, skip the comments, and get an idea of how the file is created on a high level.

<script src="https://gist-it.appspot.com/https://github.com/docker-library/php/blob/f4baf0edbc4e05e241938c68bcc7c9635707583d/7.2/stretch/apache/Dockerfile"></script>

  • At this point, one would like you to learn the following critical attributes using the Dockerfile Example:
  • The Dockerfile is a text file, and it contains the instructions for creating an image through the command line.
  • A Dockerfile is a series of instructions step by step.
  • Docker offers a collection of regular Dockerfile instructions such as `FROM`, `COPY`, `RUN`, `ENV`, `EXPOSE`, and `CMD`, to name only a few.
  • Docker will automatically build a Docker image based on the instructions in the Dockerfile.

Conclusion:

Without DevOps, production, and operations teams are likely to be conflicting in the IT world. Quality assurance of needed client functionality and benefits starts immediately after the development team begins work on a new project. Managing servers is one of the primary responsibilities of a DevOps professional through DevOps Learning.

In today's fast-paced IT world, Docker has become extremely popular. Organizations continue to integrate Docker into their production environments. DevOps Certification is aimed at professionals who implement the Docker ecosystem's core practices.

StarAgile institute provides DevOps online certification program for all aspiring professionals to learn to create Dockerfile and create containerized applications with real-time examples.