Docker on Real-World Examples
What is a software container? As its glass fellow, it stores things. In our case, it stores code, libraries, configuration files, etc. Containers are safe and scalable, when talking about software development, and quite easy to use. To work with it properly, for example to develop and launch applications with it, one will require special software, which allows for operating-system-level virtualization (containerization in one word). Docker is one of the most popular tools for it.
A traditional glass container
Advantages of Docker container
Pushing further the analogy with a glass package or jar, let’s see what else a Docker container has in its essence:
– It was made to store stuff. Just like the glass one, a Docker container stores different things and keeps them ready to use at anytime.
– It is light. A Docker container weights only tens of MBs, so you won’t need to wait for an hour until it downloads to a cloud server.
– Containers are standard. You will unlikely see new tendencies in glass containers making and the same goes for software containers – Docker has determined their shape. Now they are standard and thus quite portable.
– Containers are user-friendly.Glass jars are easy to use – they have the main part and a cover, nothing special. Docker containers also have understandable interface that is simple for new users to study out.
– Works wherever you like.You can take it to a place you like and make it work everywhere: on your own PC, on your neighbor’s one, or on a cloud service like Microsoft Azure. Moreover, you can move your container to other Docker environment without difficulties within one OS.
– It is safe.It is safer to run an app in an isolated container and Docker by default allows developers to use its whole isolating potential.
Docker container as a program
A Docker container may also appear as a program, or, to be exact, as a set of instructions managing parts of application mechanisms. In such a manner, a particular program operates within a container, allowing for sending you pieces of pages content you are surfing right now or decoding your commands in order to use them in another Docker.
A symbol of Docker
The beauty of it is the ability to run several containers at once using a single Docker. No mess up with masses of programs. Anyway, you can make your Docker list containers that you have or even make the Docker remove all containers – like any other program, it supports all the basic functions and commands.
Docker Image vs Container
Two the most basic things you come across when using Docker are Image and Container. If a container appears to be more or less clear now, then an image may need some explanation. In general, a Docker image is a set of layers that serve for code execution in a Docker container. It is a template for running your containers, so you can have a number of them based on a single image.
An image consists of a Docker file, system libraries, dependencies, tools, and settings that are important for running Docker itself. It is based on the OS kernel and most often it is Linux or Windows. So, along with, for example, a Docker Windows container, you can have a Docker image for Windows or Ubuntu as well.
Creating a Docker container
To use a container, it is good to create it at first. Let’s have another analogy for better understanding. All in all, the process of making a container somehow reminds of a layer cake, so we will use this idea and see “container baking” from the inside.
Your potential result
Here are the steps and main points of creating a container:
– At first, you will need a Dockerfile. It is a text file with a set of commands for performing the creation of a container. In our analogy let it be a cake recipe. It contains explanations of layers usage, such as libraries and so on.
– A recipe and ingredients (your code, for example, or various settings) together compose a Docker imagethat was mentioned above. In our example, a Docker image is the dough, which can be used to bake many cakes (just imagine that the dough is limitless).
– Then comes icing. It appears to be libraries that we implement for work. The main difference from real life here is that you should put icing before baking.
– Don’t forget about filling of course. It is the code you’ve written for your application. It is the main part of an app – without it you will get a dry and tasteless cake.
So, the preparation phase is over. Now it is time to bake.
The oven you may use
– As you have already installed your oven (a Docker platform that can be downloaded), you should run it. To do so, open your command line and write “ docker run  ”. It’s like igniting the oven.
– In a few moments you will get your cake ready. The baked delicious cake is your Docker container.
– The last and final stage is eating your cake. It is the usage of your application. The easiest and most pleasant part of the process.
– Still, you can always put the cake in the freezer. Just make your docker stop container in order to use it later.
Of course, it takes time and efforts to create a container, but as a result you will get a tool for easier work with applications and a great possibility to develop them in isolation from the system in general.