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Docker | Image | Container | VM | Containerd

Docker:
  • Docker is an engine by Docker. Explore slides.
  • Runs on host OS as well as guest OS, bare metal, cloud.
Image:
  • Packages software code, run-time, system tools, system libraries and settings.
  • Images become containers when they run on Docker Engine.
Container: 
  • Standard unit of software.
  • Isolate software from its environment
  • Software run same on Windows and Linux.
  • Could be portable anywhere.
  • Abstraction at the app layer that packages code and all dependencies together.
  • Runs application quickly from one computing env. to another env.
  • Do not require an OS per application, as it share the machine’s OS system kernel
  • Applications are safer in containers
  • Multiple containers can run on the same machine
  • Each container runs as an isolated processes in user space.
  • Require less space than VM.
Virtual Machines:
  • VMs are an abstraction of physical hardware.
  • Turns one server into many servers.
  • The hypervisor allows multiple VMs to run on a single machine.
  • Each VM includes a full copy of an operating system, the application, necessary binaries and libraries - taking up tens of GBs.
  • VMs can also be slow to boot.
Containerd:
  • Daemon available for Linux and Windows.
  • Manage by CNCF - Cloud Native Computing Foundation.
  • Designed to be used by Docker and Kubernetes and any other container platform
  • Docker, Kubernetes, Cloud Foundry, Fire Cracker and others are using.
  • Manages complete life cycle of the container on its host system.
  • Manages image transfer, storage  to container execution, supervision to low level storage to network attachments,  and beyond.
  • Abstract away syscalls or OS specific functionality to run containers on linux, windows, solaris, or other OSes.
  • Abstraction layer between management code and the syscalls.
  • Duct tape of features to run a container.
  • Complete storage and distribution system that supports both OCI and Docker image formats.
  • Networking are out of scope for containerd.
  • Provides push and pull functionality as well as image management.
  • You get container life-cycle APIs to create, execute, and manage containers and their tasks.
  • An entire API dedicated to snapshot management. 
  • Provides everything that you need to build a container platform without having to deal with the underlying OS details. 
  • Having a versioned and stable API that will have bug fixes and security patches backported.
Ref.:
https://www.docker.com/resources/what-container
https://www.docker.com/blog/what-is-containerd-runtime/
Explore -
Docker Network,
Docker Network
 7 layers (level) of OSI
Docker v/s Kubernetes
Weave v/s Calico
Weave
VXLAN
What is VXLAN
VXLAN White papers

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