Docker Overview

OVERVIEW

Docker is the company driving the container movement and the only container platform provider to address every application across the hybrid cloud. Today’s businesses are under pressure to digitally transform but are constrained by existing applications and infrastructure while rationalizing an increasingly diverse portfolio of clouds, datacenters and application architectures. Docker enables true independence between applications and infrastructure and developers and IT ops to unlock their potential and creates a model for better collaboration and innovation.

A little intro to LXC: -

LXC (LinuX Containers) is a OS-level virtualization technology that allows creation and running of multiple isolated Linux virtual environments (VE) on a single control host. These isolation levels or containers can be used to either sandbox specific applications, or to emulate an entirely new host. LXC uses Linux’s cgroups functionality, which was introduced in version 2.6.24 to allow the host CPU to better partition memory allocation into isolation levels called namespaces . Note that a VE is distinct from a virtual machine (VM), as we will see below.

Docker, previously called dotCloud, was started as a side project and only open-sourced in 2013. It is really an extension of LXC’s capabilities. This it achieves using a high-level API that provides a lightweight virtualization solution to run processes in isolation. Docker is developed in the Go language and utilizes LXC, cgroups, and the Linux kernel itself. Since it’s based on LXC, a Docker container does not include a separate operating system; instead it relies on the operating system’s own functionality as provided by the underlying infrastructure. So Docker acts as a portable container engine, packaging the application and all its dependencies in a virtual container that can run on any Linux server.

What They Do:-

Think of LXC as supercharged chroot on Linux. It allows you to not only isolate applications, but even the entire OS. Its helper scripts focus on creating containers as lightweight machines - basically servers that boot faster and need less RAM. There are two user-space implementations of containers, each exploiting the same kernel features:

·       Libvirt, which allows the use of containers through the LXC driver by connecting to 'lxc:///'. This can be very convenient as it supports the same usage as its other drivers.

·    Another implementation, called simply 'LXC', is not compatible with libvirt, but is more flexible with more userspace tools. It is possible to switch between the two, though there are peculiarities which can cause confusion.

What is a Container?

A container image is a lightweight, stand-alone, executable package of a piece of software that includes everything needed to run it: code, runtime, system tools, system libraries, settings. Available for both Linux and Windows based apps, containerized software will always run the same, regardless of the environment. Containers isolate software from its surroundings, for example differences between development and staging environments and help reduce conflicts between teams running different software on the same infrastructure.

LIGHTWEIGHT: -

Docker containers running on a single machine share that machine's operating system kernel; they start instantly and use less compute and RAM. Images are constructed from filesystem layers and share common files. This minimizes disk usage and image downloads are much faster.

STANDARD: -

Docker containers are based on open standards and run on all major Linux distributions, Microsoft Windows, and on any infrastructure including VMs, bare-metal and in the cloud.

SECURE: -

Docker containers isolate applications from one another and from the underlying infrastructure. Docker provides the strongest default isolation to limit app issues to a single container instead of the entire machine.

Comparing Containers and Virtual Machines

Containers and virtual machines have similar resource isolation and allocation benefits, but function differently because containers virtualize the operating system instead of hardware. Containers are more portable and efficient.

Containers and Virtual Machines Together: -

Containers and VMs used together provide a great deal of flexibility in deploying and managing apps.

Container Standards and Industry Leadership: -

The launch of Docker in 2013 jump started a revolution in app development - by bringing software containers to the masses. In just a few years, Docker has transformed the industry with a new lexicon, framework and standards in app development, packaging and management.

Starting with the pivot of dotCloud and turning a piece of dotCloud into a better Linux container technology - one that is portable, flexible, and easy to deploy. Docker open sourced the libcontainer and partnered with a worldwide community of contributors to further its development. By June 2015, just a couple short years later, Docker donated the specification and runtime code now known as runC, to the Open Container Initiative (OCI) to help establish standardization as the container ecosystem grows and matures.

Following this evolution, Docker continues to give back with the containerd project. Containerd is the core container runtime of the Docker engine daemon, an industry-standard container runtime with an emphasis on simplicity, robustness and portability, designed as an embeddable component for higher level systems. Docker engine is built on runC and containerd. This collaborative project enables portability for developers, container standardization through the OCI, a growing ecosystem of tools, and a free marketplace of images - pre-made apps that the community can share and build on.

Advantages:-

MODERN APP PLATFORM: -

The Docker platform is the only container platform to build, secure and manage the widest array of applications from development to production both on premises and in the cloud. Docker Community Edition [CE] empowers developers with tools to build applications and Docker Enterprise Edition [EE] provides IT with multi-architecture operations at scale. Docker delivers both an engine for innovation that modernizes without disruption while reducing total costs by more than 50%. Unlike other solutions that specialize in a narrow slice of the enterprise IT portfolio, Docker delivers operations at scale by addressing a diverse set of applications and infrastructure for both developers and IT.

Simplicity

Docker makes powerful tools for application creation and orchestration, accessible to everyone.

Openness

Built with open source technology and a modular design makes it easy to integrate into your existing environment.

Independence

Docker creates a separation of concerns between developers and IT and between applications and infrastructure to unlock innovation.

(Source: docker.com)