# Day 16 - Docker for DevOps Engineers. #### Introduction to Virtualization and Containerization **What is Virtualization?** Virtualization is a technology that allows for the efficient utilization of physical computer hardware by creating multiple virtual machines (VMs) on a single physical machine. Each VM runs its own operating system (OS) and behaves like an independent computer, despite sharing the underlying hardware. This abstraction layer over the hardware enhances flexibility and resource efficiency and is a foundational technology for cloud computing. ![WHAT IS A HYPERVISOR?](https://1.bp.blogspot.com/-KJ9Dgmpe8Y8/XyqOPtsue8I/AAAAAAAACS4/sZxb4XUV4UcoaX9qTiIAS34nRYKP3jWMACLcBGAsYHQ/s407/Type%2B1%2BHypervisor.png align="center") **What is Containerization?** Containerization packages software code along with its dependencies and libraries into a single executable unit called a container. Unlike VMs, containers share the host OS's kernel but remain isolated from each other. This approach is more resource-efficient and portable, making containers ideal for modern cloud-native applications. ![Containerization: Is it the solution that solves your DevOps issues ...](https://blog.jdriven.com/uploads/2019/07/container_1.png align="left") #### Understanding Docker **What is Docker?** Docker is an open-source platform designed to automate the deployment, scaling, and management of applications using containerization. It enables developers to package applications along with their dependencies into containers, ensuring consistent behavior across different environments. **Advantages of Docker:** * **Rapid Deployment:** Quick and efficient application deployment. * **Resource Efficiency:** No need for pre-allocating RAM. * **CI Efficiency:** Build applications once and run them anywhere. * **Cost-Effective:** Lightweight and requires fewer resources. * **Portability:** Containers can run on physical hardware, VMs, or cloud environments. * **Isolation:** Ensures applications run in isolation, improving security and stability. **Disadvantages of Docker:** * Not ideal for applications requiring a rich GUI. * Management complexity increases with a large number of containers. * Limited cross-platform compatibility (e.g., Windows containers can't run on Linux). * Best suited for environments where the development and testing OS are the same. * No built-in solution for data recovery and backup. #### Docker Architecture **Key Components:** * **Docker Daemon:** Runs on the host OS, managing containers and services. * **Docker Client:** CLI used to interact with the Docker daemon. * **Docker Host:** The environment where Docker runs, including the daemon, images, containers, networks, and storage. * **Docker Registry:** Stores Docker images. Public registries like Docker Hub and private registries are available. * **Docker Images:** Read-only templates used to create containers. * **Docker Containers:** Instances of Docker images, running isolated processes. #### Installation of Docker 1. **Update your package list:** ```bash ubuntu@ip-172-31-25-83:~$ sudo apt-get update ``` 2. **Install Docker:** ```bash ubuntu@ip-172-31-25-83:~$ sudo apt-get install docker.io -y ``` 3. **Verify Docker installation:** ```bash ubuntu@ip-172-31-25-83:~$ docker --version # or ubuntu@ip-172-31-25-83:~$ docker -v ``` 4. **Check Docker service status:** ```bash ubuntu@ip-172-31-25-83:~$ service docker status ``` #### Hands-On Tasks **1\. Start a New Container** Use the `docker run` command to start a new container and interact with it. **Command:** ```bash ubuntu@ip-172-31-25-83:~$ sudo docker run hello-world ``` This command pulls the `hello-world` image from Docker Hub and runs it in a new container, verifying your Docker installation. **2\. View Detailed Information** Use the `docker inspect` command to view detailed information about a container or image. **Command:** ```bash ubuntu@ip-172-31-25-83:~$ sudo docker inspect ``` **Example:** ```bash ubuntu@ip-172-31-25-83:~$ sudo docker inspect hello-world ``` This command provides comprehensive details about the container or image, including configuration and state information. **3\. List Port Mappings** Use the `docker port` command to list the port mappings for a container. **Command:** ```bash ubuntu@ip-172-31-25-83:~$ sudo docker port ``` This command shows which ports are exposed and mapped to the host system for the specified container. **4\. View Resource Usage Statistics** Use the `docker stats` command to view resource usage statistics for one or more containers. **Command:** ```bash ubuntu@ip-172-31-25-83:~$ sudo docker stats ``` This command provides real-time statistics on CPU, memory, network, and disk usage. **5\. View Running Processes** Use the `docker top` command to view the processes running inside a container. **Command:** ```bash ubuntu@ip-172-31-25-83:~$ sudo docker top ``` This command displays the active processes within the specified container. **6\. Save an Image to a Tar Archive** Use the `docker save` command to save an image to a tar archive. **Command:** ```bash ubuntu@ip-172-31-25-83:~$ sudo docker save -o ``` **Example:** ```bash ubuntu@ip-172-31-25-83:~$ sudo docker save -o hello-world.tar hello-world ``` This command exports the image to a tar archive for backup or transfer. **7\. Load an Image from a Tar Archive** Use the `docker load` command to load an image from a tar archive. **Command:** ```bash ubuntu@ip-172-31-25-83:~$ sudo docker load -i ``` **Example:** ```bash ubuntu@ip-172-31-25-83:~$ sudo docker load -i hello-world.tar ``` This command imports the image from a tar archive into the local Docker repository. ### Conclusion Docker is a crucial tool for DevOps engineers, streamlining the development, deployment, and management of applications through containerization. By mastering these Docker commands, you can efficiently handle containers and images, ensuring a smooth and reliable workflow. Thank you for reading! I hope you found this post helpful. Feel free to share your thoughts and experiences in the comments. ~ Tushar Ranjan🙂