Day 12 Task: Docker for DevOps Engineers

🗼Docker

Docker is a software platform that allows you to build, test, and deploy applications quickly. Docker packages software into standardized units called containers that have everything the software needs to run including libraries, system tools, code, and runtime. Using Docker, you can quickly deploy and scale applications into any environment and know your code will run.

🗼Docker architecture

Docker uses a client-server architecture. The Docker client talks to the Docker daemon, which does the heavy lifting of building, running, and distributing your Docker containers. The Docker client and daemon can run on the same system, or you can connect a Docker client to a remote Docker daemon. The Docker client and daemon communicate using a REST API, over UNIX sockets or a network interface. Another Docker client is Docker Compose, that lets you work with applications consisting of a set of containers.

🗼Docker daemon

The Docker daemon (dockerd) listens for Docker API requests and manages Docker objects such as images, containers, networks, and volumes. A daemon can also communicate with other daemons to manage Docker services.

🗼Docker client

The Docker client (docker) is the primary way that many Docker users interact with Docker. When you use commands such as docker run, the client sends these commands to dockerd, which carries them out. The docker command uses the Docker API. The Docker client can communicate with more than one daemon.

🗼Docker registries

A Docker registry stores Docker images. Docker Hub is a public registry that anyone can use, and Docker looks for images on Docker Hub by default. You can even run your own private registry.

When you use the docker pull or docker run commands, Docker pulls the required images from your configured registry. When you use the docker push command, Docker pushes your image to your configured registry.

🗼Docker objects

When you use Docker, you are creating and using images, containers, networks, volumes, plugins, and other objects. This section is a brief overview of some of those objects.

Images

An image is a read-only template with instructions for creating a Docker container. Often, an image is based on another image, with some additional customization. For example, you may build an image which is based on the ubuntu image, but installs the Apache web server and your application, as well as the configuration details needed to make your application run.

Containers

A container is a runnable instance of an image. You can create, start, stop, move, or delete a container using the Docker API or CLI. You can connect a container to one or more networks, attach storage to it, or even create a new image based on its current state.

🗼Advantages of docker

Docker provides several advantages that make it a popular choice for software development, deployment, and management. Here are some key advantages of using Docker:

1. Consistency Across Environments

2. Isolation

3. Portability

4. Rapid Deployment

5. Resource Efficiency

   🗼Limitations of Docker

   Docker has a few limitations, including:

   • Security: Docker containers are not completely isolated from the host system. This means that if a container is compromised, the host system could also be compromised.

   • Performance: Docker containers can add overhead to the host system. This can reduce the performance of the host system.

   • Complexity: Docker can be complex to learn and use. This can be a barrier to adoption for some users.

   • 🗼Basic Commands:

     • docker run: Creates and starts a new container from an image.

     • docker ps: Lists running containers.

     • docker ps -a: Lists all containers (including stopped ones).

     • docker stop and docker start: Stops and starts containers, respectively.

     • docker rm: Removes one or more containers.

     • docker rmi: Removes one or more images.