Docker

Docker vs VM

Userspace vs Kernel space

• There is only one shared kernel
  • Container is like a packaged userspace applications
  • There is no separate kernel in container
  • Normal or containerized applications (via syscall) same shared Linux kernel. It is host’s kernel
  • Docker engine check to support host kernel
• If host’s kernel is changed, will the old container continue to work properly?
  • Not sure
• In non-linux, what is the kernel to share? Technically via a Linux VM
  • Docker for Windows uses Linux VM (Hyper-V), or Linux Subsystem in Win10
  • Docker for MacOS uses xhyve Virtual Machine
• There is Windows Container, which could share Window kernel

Docker overview

Official docs

Docker engine includes:

• Docker daemon (dockerd): act as a server
• REST API: provides interface to docker daemon
• CLI (docker command): uses REST API

Image, container, docker hub/registry.

Using docker

Docker get started

• Image and Container
• Service
• Swarm
• Stack