00:00:00 How does Docker work?

00:00:02 There are two most important concepts in Docker, images and containers, and the entire workflow revolves around them.

00:00:11 Let's start with images.

00:00:13 A Docker image is a lightweight, standalone, executable package that includes everything needed to run a piece of software,

00:00:22 including the code, runtimes like Node.js, libraries, system tools, and even the operating system.

00:00:30 Think of a Docker image as a recipe for our application.

00:00:34 It not only lists the ingredients, being code and libraries, but also provides the instructions such as runtime and system tools to create a specific meal,

00:00:44 meaning to run our application.

00:00:48 And we would want to run this image somewhere, right?

00:00:51 And that's where containers come in.

00:00:53 A Docker container is a runnable instance of a Docker image.

00:00:58 It represents the execution environment for a specific application, including its code, runtime, system tools, and libraries included in the Docker image.

00:01:09 A container takes everything specified in the image and follows its instructions by executing necessary commands, downloading packages,

00:01:17 and setting things up to run our application.

00:01:20 Once again, imagine having a recipe for a delicious cake, the recipe being the Docker image.

00:01:26 Now, when we actually bake the ingredients, we can serve it as a cake, right?

00:01:31 The baked cake is like a Docker container.

00:01:34 It's the real thing created from the recipe.

00:01:38 Just like we can have multiple servings of the same meal from a single recipe, or multiple documents created from a single database schema,

00:01:46 We can run multiple containers from a single image.

00:01:49 That's what makes Docker the best.

00:01:51 We create one image and get as many instances as we want from it in form of containers.

00:01:58 Now, if you dive deeper into Docker, you'll also hear people talk about volumes.

00:02:03 A Docker volume is a persistent data storage mechanism that allows data to be shared between a Docker container and the host machine,

00:02:13 which is usually a computer or a server, or even among multiple containers.

00:02:18 It ensures data durability and persistence even if the container is stopped or removed.

00:02:25 Think of it as a shared folder or a storage compartment that exists outside the container.

00:02:31 The next concept is Docker Network.

00:02:34 It's a communication channel that enables different Docker containers to talk to each other or with the external world.

00:02:41 It creates connectivity, allowing containers to share information and services while maintaining isolation.

00:02:49 Think of a Docker network as a big restaurant kitchen.

00:02:52 In a large kitchen, being the host, you have different cooking stations, or containers, each focused on a specific meal.

00:03:01 Meal being our application.

00:03:03 Each cooking station, or a container, is like a chef working independently on a meal.

00:03:09 Now imagine a system of order tickets or a Docker network connecting all of these cooking stations together.

00:03:16 Chefs can communicate, ask for ingredients, or share recipes seamlessly.

00:03:22 Even though each station or a container has its own space and focus, the communication system or the Docker network enables them to collaborate efficiently.

00:03:33 They share information without interfering with each other's cooking process.

00:03:38 I hope it makes sense, but don't worry if it doesn't.

00:03:41 We'll explore it together in the demo.

00:03:43 So moving on, the Docker workflow is distributed into three parts.

00:03:48 Docker client.

00:03:50 Docker host AKA Docker daemon and Docker registry AKA Docker hub.

00:03:57 The Docker client is the user interface for interacting with Docker.

00:04:01 It's the tool we use to give Docker commands.

00:04:05 We issue commands to the Docker client via the command line or a graphical user interface, instructing it to build, run,

00:04:13 or manage images or containers.

00:04:16 Think of the Docker client as the chef giving instructions to the kitchen staff.

00:04:21 The Docker host or Docker daemon is the background process responsible for managing containers on the host system.

00:04:29 It listens for Docker client commands, creates and manages containers, builds images and handles other Docker related tasks.

00:04:38 Imagine the Docker host as the master chef overseeing the kitchen, carrying out instructions given by the chef or the Docker client.

00:04:47 Finally, the Docker registry, aka Docker Hub, is a centralized repository of Docker images.

00:04:55 It hosts both public and private registries or packages.

00:04:59 Docker is the Docker Hub, what Git is the GitHub in a nutshell.

00:05:04 Docker images are stored in these registries, and when you run a container, Docker may pull the required image from the registry if it's unavailable locally.

00:05:14 To return to our cooking analogy, think of Docker registry as a cookbook or recipe library.

00:05:21 It's like a popular cookbook store where you can find and share different recipes, in this case, Docker images.

00:05:29 In essence, the Docker client is the command center where we issue instructions.

00:05:34 The Docker host then executes these instructions and manages containers.

00:05:39 And the Docker registry serves as a centralized storage for sharing and distributing images.