DOCKER - Basics
krishna prasad kondra4 min read
what is a container? Generally, a container is a bundle of applications and application libraries required to run your application with the minimum system dependencies.
What is the difference between containers and virtual machines? Containers and virtual machines are both technologies used to isolate applications and their dependencies, but with some key differences:
| Feature | Containers | Virtual Machines (VMs) |
| Architecture | Share the host OS kernel | Include a full OS instance |
| Isolation | Process-level isolation | Hardware-level isolation |
| Boot Time | Usually in seconds | Usually in minutes |
| Resource Usage | Lightweight (only necessary libraries and binaries) | Heavy (full OS and applications) |
| Use Case | Microservices, rapid deployment, scalable systems | Monolithic applications, full OS testing |
| Deployment Size | Small (megabytes) | Large (gigabytes) |
| Startup Time | Fast (seconds) | Slow (minutes) |
| Host Dependency | Must use the same OS kernel as the host | Can run a different OS than the host |
| Management Tools | Docker, Kubernetes | VMware, Hyper-V, VirtualBox |
| Security | Shares the host OS kernel, less isolation | Strong isolation, each VM is a separate OS instance |
| Lifecycle Management | Easier to create, deploy, and destroy | More complex management and maintenance |
What is docker? Docker is a containerization platform that helps to easily containerize applications. In simple words, containerization is a concept and Docker implements this concept.
what are the docker components.? Docker has several core components that work together to facilitate containerization. Here’s a breakdown of the key Docker components:
| Component | Description |
| Docker Engine | Core part of Docker, responsible for creating and managing Docker containers. It consists of the Docker daemon, a REST API, and a CLI. |
| Docker Daemon | Background service running on the host that manages Docker images, containers, networks, and storage volumes. |
| Docker CLI | Command-line interface that allows users to interact with the Docker daemon through commands. |
| Docker Images | Read-only templates used to create Docker containers. They contain the application code, runtime, libraries, environment variables, and configuration files. |
| Docker Containers | Lightweight, portable, and executable packages that run instances of Docker images. Containers share the host OS kernel. |
| Dockerfile | A text file containing instructions for building a Docker image. It specifies the base image and the steps to install dependencies and copy application code. |
| Docker Hub | A cloud-based registry service where Docker users can create, store, and distribute Docker images. It includes both public and private repositories. |
| Docker Compose | A tool for defining and running multi-container Docker applications. It uses a YAML file to configure the application’s services, networks, and volumes. |
| Docker Swarm | Native clustering and orchestration tool for Docker. It allows users to create and manage a swarm of Docker nodes (servers) as a single virtual system. |
| Docker Registry | A storage and distribution system for Docker images. Docker Hub is a public registry, but private registries can also be set up. |
| Docker Volume | A method for persisting data generated and used by Docker containers. Volumes are managed by Docker and can be shared among multiple containers. |
| Docker Network | Enables communication between Docker containers, whether on the same host or across different hosts. Docker provides several networking options, such as bridge, host, overlay, and macvlan. |
- Explain the docker lifecycle with the commands used.
Docker Lifecycle and Key Commands
| Lifecycle Stage | Description | Docker Commands |
| Build Image | Create a Docker image from a Dockerfile. | docker build -t myapp:latest . |
| Run Container | Create and start a container from an image. | docker run -d --name myapp_container myapp:latest |
| List Containers | List running containers. | docker ps |
| Stop Container | Stop a running container. | docker stop myapp_container |
| Start Container | Start a stopped container. | docker start myapp_container |
| Remove Container | Remove a stopped container. | docker rm myapp_container |
| List Images | View all available Docker images. | docker images |
| Remove Image | Delete an image. | docker rmi myapp:latest |
| Push Image | Upload an image to a registry (e.g., Docker Hub). | docker push myusername/myapp:latest |
| Pull Image | Download an image from a registry. | docker pull myusername/myapp:latest |
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Written by
krishna prasad kondra
krishna prasad kondra
Currently, Learning the ways of cloud and DevOps.