Lecture on Containers and Docker

Introduction to Containers

• Containers include everything needed for an app to run: code, libraries, and OS.
• They are fast, portable, and isolated environments.
• Containers vs VMs:
  • Both provide isolated environments.
  • Containers are quicker and less resource-intensive.
  • Containers share the host's kernel, unlike VMs that use hypervisor layers.
• Kernel: Core of OS, manages CPU, memory, I.O., file systems, and process management.

Benefits for Developers

• Multiple environments can be managed simultaneously.
• Solution to "it works on my machine" problem:
  • Containers ensure consistent environments across different machines.
• Legacy systems and new technologies can coexist without conflict.

Creating a Container

• Requires a container platform (e.g., Docker).
• Containers run from a base file system, presented as container images.
• Images consist of overlapping layers, similar to source control.

Docker and Container Images

• Use of Dockerfile:
  • Commands to build images, executed in sequence.
  • Each command generates a new file system or metadata layer.
• From a single image, multiple containers can run:
  • New file system layer for each container.
  • Container runtime changes do not affect others.
• Containers can be stopped and started without data loss.

Interacting with Containers

• Containers can be accessed similarly to VMs (e.g., starting a shell in Linux containers).
• Simple communication between containers due to virtualized network layers.

Publishing and Deployment

• Tag containers (e.g., version tagging) and publish to a container registry.
• Container registry stores images online.
• Default registry is Docker's, but others can be used.
• Cloud platforms often support container deployment.
• Custom deployment with compatible container runtime is possible.

Advanced: Container Orchestration

• Platforms like Kubernetes enable creation of container-based clouds.
• Kubernetes handles deployment details based on declarative state descriptions.

Conclusion

• Containers provide a flexible and efficient development and deployment environment.
• Encouragement to support further content creation.