Goals

• Understand Container Technology at a High Level
• Understand the Appeal/Benefits of Containers
• Provide a Starting Point for Working with Docker
• Have Fun - Docker is cool

Agenda

• What is a container?

• How do containers work?

• Why use containers? (Evolution of applications)

• Docker

• Awesome Demo

• What Now?

What is a Container?

• Multiple Definitions

  • OS Containers vs. Application Containers

  • Many Implementations

• Container Technologies

  • FreeBSD Jail - 2000

  • Solaris - 2004

  • LXC - 2008

  • Docker - 2013

  • CoreOS rkt (pronounced rocket)

  • https://en.wikipedia.org/wiki/Operating-system-level_virtualization

Container Essentials

• Kernel Virtualization

• ​Isolated, resource controlled, and portable operating environment

Analogies

• Lightweight VM?
  • Kinda... Not Really...
  • CLI Only
• ​chroot on Steroids
• Obligatory Shipping Analogy
  • Container Runtime is a Shipping Barge
  • Containers are Standardized Shipping Crates
• Group of processes with extended isolation capabilities

How do Containers Work?

• Linux Kernel
  • You can create a container with standard shell commands
• Kernel Technologies
  • Namespaces
  • Control Groups (cgroups)
  • Union File System
  • Container Format
• Windows has similar concepts for Server 2016

Namespaces

• Process with entirely separate machine view
• Linux Namespaces
  • mount - mount points
  • UTS - Host name
  • IPC - Inter Process Communication (message queues, etc...)
  • Network - network devices, stacks, and ports
  • User - user and group IDs
  • PID - process IDs

Control Groups (cgroups)

• Regulates the resource usage for a collection of processes
  • ​CPU
  • memory
  • disk I/O
  • network
  • devices
• ​Features
  • Resource limiting
  • Prioritization
  • Accounting
  • Control

Union File System

• Separate file systems overlaid forming a single coherent file system
• Drivers
  • UnionFS - 1990
  • AUFS - 2006​
  • Btrfs
  • devicemapper
  • overlayfs/overlay2
  • Many More
• ​Driver set on Docker Daemon
• Why?
  • Performance
  • Shared Storage

Union File System

Container Format

• Packages namespaces, cgroups, and UnionFS into a wrapper
• Typically aligns Namespace and cgroup boundaries
• Competing Container Formats
  • LXC
  • appc - CoreOS rkt
  • libcontainer - Docker
• OCI (Open Container Initiative)
  • Standards for container formats and runtimes
  • None are in full compliance YET

Evolution of Applications

Why Use Containers?

Long Live Hypervisor!

• Hypervisor is not dead
• Container Runtime on top of Hypervisor
• Advantages
  • Install any OS side-by-side
  • Security Isolation between host and VM
• Hypervisor Containers
• VM on Container Runtimes

Docker

• Made containers easy by providing a simplistic CLI
• Image Distribution
• Components
  • Docker Engine
  • Images
  • Registries

Docker Engine

• Server (Daemon)
  • dockerd
  • Responsible for container operations
• REST API
  • Sends commands to server
• Client (CLI)
  • Issues commands to the REST API

Images

• Complete IMMUTABLE Union File System
• Layered
  • Each layer is interchangeable
  • Containers can share layers
  • Writable top layer at runtime

Images & UnionFS

Registries

• Repository for managing images
  • Similar to NPM or Nuget except with images instead of packages
• Distribute images easily
  • Major contributing factor to the success of docker
• Examples
  • Docker Hub
  • Quay
  • Private

Docker for Windows/Mac

• Creates Linux Alpine machine in hypervisor
• Not intended for production scenarios
• Do not confuse with Docker ON windows
  • MS implemented containers for Server 2016
  • Linux and Windows containers don't run side by side

Docker on Windows

• https://www.youtube.com/watch?v=85nCF5S8Qok

(https://blog.docker.com/2016/09/dockerforws2016/)