Jeff Nickoloff - Docker in Action

This chapter covers

What Docker is

An introduction to containers

How Docker addresses software problems that most people tolerate

When, where, and why you should use Docker

Example: Hello, World

If youre anything like me, you prefer to do only exactly what is necessary to accomplish an unpleasant or mundane task. Its likely that youd prefer tools that are simple to use to great effect over those that are complex or time consuming. If Im right, then I think youll be interested in learning about Docker.

Suppose you like to try out new Linux software but are worried about running something malicious. Running that software with Docker is a great first step in protecting your computer because Docker helps even the most basic software users take advantage of powerful security tools.

If youre a system administrator, making Docker the cornerstone of your software management toolset will save you time and let you focus on high-value activities because Docker minimizes the time that youll spend doing mundane tasks.

If you write software, distributing your software with Docker will make it easier for your users to install and run. Writing your software in a Docker-wrapped development environment will save you time configuring or sharing that environment, because from the perspective of your software, every environment is the same.

Suppose you own or manage large-scale systems or data centers. Creating build, test, and deployment pipelines is simplified using Docker because moving any software through such a pipeline is identical to moving any other software through.

Launched in March 2013, Docker works with your operating system to package, ship, and run software. You can think of Docker as a software logistics provider that will save you time and let you focus on high-value activities. You can use Docker with network applications like web servers, databases, and mail servers and with terminal applications like text editors, compilers, network analysis tools, and scripts; in some cases its even used to run GUI applications like web browsers and productivity software.

NOT JUST LINUX Docker is Linux software but works well on most operating systems.

Docker isnt a programming language, and it isnt a framework for building software. Docker is a tool that helps solve common problems like installing, removing, upgrading, distributing, trusting, and managing software. Its open source Linux software, which means that anyone can contribute to it, and it has benefited from a variety of perspectives. Its common for companies to sponsor the development of open source projects. In this case, Docker Inc. is the primary sponsor. You can find out more about Docker Inc. at https://docker.com/company/.

Docker is a command-line program, a background daemon, and a set of remote services that take a logistical approach to solve common software problems and simplify your experience installing, running, publishing, and removing software. It accomplishes this using a Unix technology called containers.

Historically, Unix-style operating systems have used the term jail to describe a modified runtime environment for a program that prevents that program from accessing protected resources. Since 2005, after the release of Suns Solaris 10 and Solaris Containers, container has become the preferred term for such a runtime environment. The goal has expanded from preventing access to protected resources to isolating a process from all resources except where explicitly allowed.

Using containers has been a best practice for a long time. But manually building containers can be challenging and easy to do incorrectly. This challenge has put them out of reach for some, and misconfigured containers have lulled others into a false sense of security. We need a solution to this problem and Docker helps. Any software run with Docker is run inside a container. Docker uses existing container engines to provide consistent containers built according to best practices. This puts stronger security within reach for everyone.

With Docker, users get containers at a much lower cost. As Docker and its container engines improve, you get the latest and greatest jail features. Instead of keeping up with the rapidly evolving and highly technical world of building strong application jails, you can let Docker handle the bulk of that for you. This will save you a lot of time and money and bring peace of mind.

Without Docker, businesses typically use hardware virtualization (also known as virtual machines) to provide isolation. Virtual machines provide virtual hardware on which an operating system and other programs can be installed. They take a long time (often minutes) to create and require significant resource overhead because they run a whole copy of an operating system in addition to the software you want to use.