Do you want to improve your skills in website and software monitoring? Are you already working on platforms and want to learn how to containerize an application to host it on Kubernetes? Jedha offers you the best data engineering training to do so. We offer you a training on Docker and Kubernetes. Let's focus on Docker in this article!
In the world of container platforms, Docker occupies a prominent place. Indeed, this containerisation solution is undoubtedly the most popular and the most used. Discover the essentials of Docker technology through its definition, its mode of operation, its advantages and disadvantages as well as some concrete use cases.
Docker: what is it really?
Docker is an open source software developed in 2013 by Solomon Hykes. This software tool is used for the creation, deployment and management of virtualised applications on a specific operating system. To be more explicit, Docker takes care of gathering the services or functions, different libraries, configuration files, dependencies and other components of an application within a container. Each running container shares all the services of the operating system that hosts the application virtualised by the Docker platform.
In its very first versions, Docker was only compatible with Linux. Today, the tool can work with other operating systems such as Apple macOS or Microsoft Windows. It should also be noted that some versions of Docker are specially designed for Microsoft Azure and Amazon Web Services.
When people talk about Docker, they usually refer to several terms that may seem unclear or even incomprehensible to the uninitiated. Clarifying these important concepts, however, helps to better understand the tool's contours.
Definition of key terms related to Docker
Several terminologies are specific to Docker software. Here is a definition of some of these essential notions to deepen your knowledge of this tool.
Container
Still called container, the container is very close to virtual machines. In reality, it is a set of lightweight and independent software processes, which gathers all the files required to run the processes: code, library and parameters, runtime, system tools... Containers can be used to run one or more Linux or Windows applications. The advantage with containers is that they really simplify virtualisation. In fact, virtualisation basically consists of running many operating systems on a single system.
Containers use the same operating system kernel and also isolate the application processes from the rest of the system, which they share with each other. They are therefore more efficient in terms of system resource consumption. As a result, the user can run about 4 to 6 times more application instances using containers.
Images of the container
Container images are a package of dependencies and information required to create a container. Each image has the set of dependencies (e.g. frameworks) as well as the deployment and runtime configuration settings to be implemented by a container runtime environment. In practice, an image is derived from several base images which are layers on top of each other to form the container file system.
Benchmark
Also referred to as a repository, the repository is a collection of Docker images associated and tagged with a tag that clearly specifies the version of the image. Some repositories may contain multiple variants of a specific image. The image in question may be composed of the SDKs (which are heavier or larger) or the runtimes which have the distinction of being lighter.
Dockerfile
The dockerfile is the text file that contains the steps to follow to create a Docker image. It is presented as a batch script. The first line of the text specifies the base image to start with. Then the instructions for successfully installing the required programs, copying the files and performing other operations are given. The tools provided by the dockerfile make it possible to obtain the working environment that the user needs.
Cluster
The cluster is a collection of hosts. The hosts are exposed as if they were a single virtual Docker host. This allows the application to scale to multiple instances of shared services on multiple hosts within the cluster. Docker clusters can be created with Azure Service Fabric, Docker Swarm, Kubernetes or Mesosphere DC/OS.
How does Docker work?
Docker works on a simple to understand principle. The tool includes several interesting features to provide satisfactory returns.
How it works
Docker open source software takes advantage of the Linux kernel and many of its features such as cgroups and namespaces. These different elements allow the tool to separate processes so that they can run autonomously or independently. This independence is notably the objective of Docker containers, which are responsible for executing several processes and applications separately from each other. The aim is tooptimise the use of the Docker users' infrastructure while guaranteeing the same level of security as that offered by separate systems.
Container tools, including the Docker software, are connected to a specific image-based deployment model. This makes sharing an application or a set of services with all their dependencies and between different environments relatively simple and easy. Furthermore, it should be noted that Docker also performs automation of application deployment within a container environment.
Installation of the tool
Before using Docker, it is of course necessary to install it. To do this, the user must launch and execute certain commands(sudo yum check-update, sudo curl -fsSL | sh). These are specific to the Centos 7 Linux distribution. To access other distributions, please refer to the official documentation of the tool. At the end of the installation, the user starts the Docker service with the following command: sudo systemctl start docker. Then, the command sudo systemctl status docker must be run for the tool to run properly.
The features
The Docker containerisation tool is based on seven (7) main components. The Docker Engine is a client-server tool with container technology. Thus, it handles the tasks of creating container-based applications. The engine generates a server-side daemon process that hosts images, storage volumes, containers and networks.
All containers created are named Dockerfiles. The Docker Compose element determines the composition of components within a dedicated container. The Docker Hub allows users to share and publish container-based applications from a common library.
The Docker Engine includes a Docker Swarm mode that primarily provides load balancing of clusters. As a result, resources from multiple hosts can be brought together to act or function as a single unit. This will make it easier for Docker users to quickly scale container deployments.
Docker training: how to master the tool?
Today, the Docker platform is very popular for the development of applications and software. It is therefore important for those who aspire to this profession to know how to use this containerisation tool, which offers interesting advantages. The skills and knowledge needed to master Docker are taught or imparted during the Data Engineer training courses.
Regardless of the learner's initial level, the Docker training course enables the learner to master the use of the software in a reasonable time. At the end of the training, the holder of the Data Engineer certification has the required know-how for data engineering and machine learning. As a data scientist, he or she can therefore easily use Docker to implement various digital projects.
Typically, training is provided by a team of skilled and qualified faculty selected by a distinguished admissions committee. These data and cybersecurity professionals have the pedagogy necessary to train in Docker technology.
The benefits of Docker
The success of this technology within a few years of its launch is no accident. Indeed, the tool has a good reputation because of its high efficiency and the interesting actions it allows professionals to perform quite simply.
A very flexible tool
The first advantage of Docker is that it is very flexible. Specifically, no matter what type or size of application, it can be transformed into a container using Docker. In addition, the tool offers users the possibility of creating, deploying and starting containers on their own computers, those of clients or a remote server.
A lightweight work tool
Docker is a fairly flexible and lightweight platform that really makes life easier for its users. Unlike traditional virtualisation, this tool uses and shares the kernel of the host operating system. This particular operation allows Docker to be very efficient when it comes to using system resources.
Docker is autonomous and independent
With Docker software, installing or uninstalling containers does not depend on other previously installed containers. This makes it possible to update or replace a container without having to modify the others.
Docker is a secure platform
This tool creates default containers by applying strict security rules. It also effectively isolates all processes.
The weaknesses of Docker
The Docker platform does not only have advantages. It has some weaknesses that you should be aware of.
Firstly, the tool can have serious difficulties in managing a large number of containers efficiently and simultaneously. Secondly, even if the security level of Docker is globally satisfactory, certain security flaws can occur when using the platform. For example, although they are isolated, Docker containers use a single operating system. Because of this, a cyber attack on the OS or a simple security breach can compromise all Docker containers. In fact, the platform recently suffered a security breach that affected around 5% of users. Of these, nearly 190,000 people had their container data exposed as a result of unauthorised access to the Hub database. At the time, Docker Inc. suggested that affected users (companies and individuals) change their passwords.
However, there is a simple solution to reduce the security issues that the software may face. This is to run the Docker containers within a virtual machine.
Businesses that use the Docker platform
Web developers and system administrators regularly use Docker software to perform some important tasks.
The developers
The use of Docker is of great interest to web and mobile application developers. By using this software, they can ensure that the applications they design will work, regardless of the operating system and environment they are running on. Docker therefore allows developers to save time and not worry about the system on which the application will run.
System administrators
The software is also used by system administrators to meet various needs. As explained above, Docker makes it easy to install and start containers that work together. System administrators combine it with docker-compose to deploy an entire application and its dependencies with a single command.
Docker software use case
To better understand the role or importance of Docker, here are three (3) use cases of this tool.
Code management
The codes that programmers create are called upon to integrate environments that are different from the frameworks in which they were designed. Each environment has its own specificity and therefore a slight variation from the other. The Docker platform eliminates this difference and provides a consistent environment that makes programming and coding much more accessible and comfortable. This is because Docker container images are immutable and therefore do not show any change, regardless of the nature of the environments.
Simplified configuration
The Docker platform allows users to place the configuration file in the code. It ensures that the environment variables are passed on in order to respond to various environments. In practical terms, this is what justifies the possibility of using a Docker image in a completely different environment.
Rapid deployment
Docker software makes rapid deployment of containers possible. In the past, developers needed days to install new hardware, get it running, provision it and make it available. With Docker software containers, this can be done in seconds.
