What Is Docker
Docker is a platform that packages applications and their dependencies into containers. Containers run consistently across laptops, test servers, and production environments.
For DevOps teams, Docker reduces environment mismatch and speeds up delivery pipelines.
Containers vs Virtual Machines
Virtual machines include a full guest operating system, while containers share the host kernel. This makes containers lighter and faster to start.
- VMs: heavier, stronger isolation, slower startup
- Containers: lightweight, portable, quick startup
- Both are useful depending on security and performance needs
Basic Docker Commands
docker --version
docker pull nginx
docker images
docker run -d -p 8080:80 nginx
docker ps
docker stop <container_id>
docker rm <container_id>These commands cover image download, container start, inspection, and cleanup.
Docker Images and Containers
An image is a read-only template. A container is a running instance of that image. You can run multiple containers from one image with different settings.
Use a Dockerfile to define how your image is built so the process is repeatable in CI/CD.
Why Docker Is Important in DevOps
- Standardized environments from development to production
- Faster onboarding and deployment consistency
- Easy integration with CI/CD pipelines and Kubernetes
- Better scaling and rollback reliability
Docker is a core building block for cloud-native DevOps workflows.