Docker for Devops
Hirenkumar G.
Expert in #Windows/#Linux #Mac #ServerConfiguration, #VMware #CloudServices, #DevopsEnthusiast #TechEnthusiast #TechnicalContentWriter #CICD #Docker #Kubernates #Aws #Azure #Terraform #Jenkins #Git #Github #Freelancer
Here are detailed notes on each Docker topic based on your PDF content:
### 1. Introduction to Docker
- Overview:
?- Released in March 2013 by Solomon Hykes and Sebastien Paul.
?- Open-source platform for creating, deploying, and running applications.
?- Utilizes OS-level virtualization through containers rather than creating full virtual machines.
?- Docker can be installed on any OS, but the Docker engine runs natively on Linux distributions.
?- Written in the Go programming language.
- Key Concepts:
?- Containerization: Running applications in isolated environments called containers.
?- Docker vs. Virtual Machines: Containers share the host OS kernel, making them more lightweight compared to VMs that require separate OS instances.
### 2. Benefits of Using Docker
- Advantages:
?- No Pre-allocation of RAM: Containers use resources on-demand.
?- CI Efficiency: Reusable images streamline the deployment process.
?- Cost-effective: Reduces overhead compared to traditional VM setups.
?- Lightweight: Quick to start and stop, minimal resource usage.
?- Flexibility: Runs on physical, virtual, or cloud hardware.
?- Image Reusability: Images can be shared and reused across environments.
### 3. Challenges with Docker
- Disadvantages:
?- Not ideal for applications requiring a rich graphical user interface (GUI).
?- Managing a large number of containers can become complex.
?- Cross-platform compatibility issues; an image built on one OS may not run on another.
?- Not a substitute for Virtual Machines when OS environments differ.
?- Lack of built-in solutions for data recovery and backup.
### 4. Docker Architecture and Components
- Components:
?- Docker Daemon: Runs on the host OS, manages containers, and communicates with other daemons.
?- Docker Client: Users interact with the daemon through commands and REST API.
?- Docker Host: Provides an environment to execute applications and contains the daemon, images, containers, networks, and storage.
?- Docker Registry: Stores Docker images (e.g., Docker Hub for public images).
### 5. Understanding Docker Images and Containers
- Images:
?- Read-only binary templates used to create containers.
?- Can be pulled from Docker Hub, created from Docker files, or derived from existing containers.
??
- Containers:
?- Instances of Docker images in execution.
?- Act as lightweight virtualized environments.
### 6. Docker Installation and Basic Commands
- Installation:?
?- Use package managers (e.g., yum install docker on AWS).
??
- Basic Commands:
?- docker images - List all images on local machine.
领英推荐
?- docker pull <image> - Download an image from Docker Hub.
?- docker run --name <container> <image> - Create and run a container with a name.
?- docker ps - List running containers.
?- docker stop <container> - Stop a running container.
?- docker rm <container> - Remove a container.
### 7. Creating and Using Dockerfiles
- Dockerfile:
?- A text file with a series of instructions to automate the image creation process.
??
- Common Instructions:
?- FROM: Specifies the base image.
?- RUN: Executes commands to create layers in the image.
?- COPY: Copies files from the local system into the image.
?- ADD: Similar to COPY, but can fetch files from URLs.
?- EXPOSE: Defines which ports the container will listen on.
?- CMD and ENTRYPOINT: Specify the commands to run in the container.
### 8. Working with Docker Volumes
- Volume Management:
?- Volumes are directories that persist data beyond the lifecycle of a container.
?- Can be shared between containers and mapped to the host system.
??
- Benefits:
?- Decouples storage from containers, allowing data persistence and sharing.
?- Volumes remain intact even after the container is deleted.
### 9. Docker Networking and Port Management
- Networking:
?- Containers can communicate over a network through exposed ports.
??
- Port Management:
?- EXPOSE: Makes a port available for communication between containers.
?- -p: Publishes a port to the host, making it accessible externally.
### 10. Advanced Docker Commands and Usage
- Commands:
?- docker exec: Executes commands in a running container.
?- docker attach: Connects to the main process of a running container.
### 11. CI/CD with Docker
- Continuous Integration/Deployment:
?- Docker enables consistent environments across development, testing, and production stages.
?- Streamlines the CI/CD pipeline by allowing the same image to be used throughout.
### 12. Comparing Docker with Virtual Machines
- Differences:
?- Docker containers are lightweight and share the host OS kernel, while VMs run separate OS instances.
?- Docker provides faster startup times and resource efficiency compared to traditional virtualization.