Docker实战2：新手进阶指南

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《Docker in Action 第二版》是一本由Manning Early Access Program (MEAPEdition) 出版的实用指南，专为Linux软件初学者和中级用户或作者设计。自第一版发布以来，容器技术世界发生了显著变化，本书旨在适应这一发展，提供最新知识。第二版的版权信息为2019年Manning Publications，读者可以在其官网www.manning.com获取更多信息。本书主要涵盖了以下几个关键知识点： 1. Docker基础知识：作为教程的起点，它会引导读者了解Docker的基本概念，包括如何安装、配置和管理Docker环境。读者将学习到如何创建、运行和停止容器，以及容器与虚拟机的区别。 2. 容器核心概念：深入探讨容器的设计原则，如轻量级、隔离性、端口映射和共享存储等，这些都是理解和使用Docker的关键要素。 3. 连续容器交付：随着DevOps实践的普及，本书会介绍如何在开发、构建和部署过程中有效地利用Docker进行自动化，实现从代码到生产环境的无缝流程。 4. 中级主题：除了基础内容，还涉及更高级的主题，如Docker Compose和Swarm集群管理、安全性和最佳实践、以及容器镜像的构建和分发。 5. 协同作者贡献：新版本引入了Stephen Kuenzlia作为合著者，两人的专业知识和经验将为读者带来更全面的视角和解决方案，共同应对快速变化的容器和编排生态系统中的挑战。 6. 用户反馈与互动：购买MEAP版本的读者可以参与Manning论坛的讨论，提出问题和分享见解，这些反馈将在书籍生产过程中得到清理和优化。《Docker in Action 第二版》是一个与时俱进的资源，不仅适合入门者提升技能，也适合有一定基础的开发者深化理解，跟随作者的脚步探索Docker在实际项目中的应用和优化策略。

This new portability helps users in a few ways. First, it unlocks a whole world of software

that was previously inaccessible. Second, it’s now feasible to run the same software—exactly

the same software—on any system. That means your desktop, your development

environment, your company’s server, and your company’s cloud can all run the same

programs. Running consistent environments is important. Doing so helps minimize any

learning curve associated with adopting new technologies. It helps software developers better

understand the systems that will be running their programs. It means fewer surprises. Third,

when software maintainers can focus on writing their programs for a single platform and one

set of dependencies, it's a huge time-saver for them and a great win for their customers.

Without Docker or virtual machines, portability is commonly achieved at an individual

program level by basing the software on some common tool. For example, Java lets

programmers write a single program that will mostly work on several operating systems

because the programs rely on a program called a Java Virtual Machine (JVM). Although this is

an adequate approach while writing software, other people, at other companies, wrote most of

the software we use. For example, if there is a popular web server that I want to use, but it

was not written in Java or another similarly portable language, I doubt that the authors would

take time to rewrite it for me. In addition to this shortcoming, language interpreters and

software libraries are the very things that create dependency problems. Docker improves the

portability of every program regardless of the language it was written in, the operating system

it was designed for, or the state of the environment where it’s running.

1.2.3 Protecting your computer

Most of what I've mentioned so far have been problems from the perspective of working with

software and the benefits of doing so from outside a container. But containers also protect us

from the software running inside a container. There are all sorts of ways that a program might

misbehave or present a security risk:

• A program might have been written specifically by an attacker.

• Well-meaning developers could write a program with harmful bugs.

• A program could accidentally do the bidding of an attacker through bugs in its input

handling.

Any way you cut it, running software puts the security of your computer at risk. Because

running software is the whole point of having a computer, it’s prudent to apply the practical

risk mitigations.

Like physical jail cells, anything inside a container can only access things that are inside it

as well. There are exceptions to this rule but only when explicitly created by the user.

Containers limit the scope of impact that a program can have on other running programs, the

data it can access, and system resources. Figure 1.7 illustrates the difference between running

software outside and inside a container.

©Manning Publications Co. We welcome reader comments about anything in the manuscript - other than typos and

other simple mistakes. These will be cleaned up during production of the book by copyeditors and proofreaders.

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The container abstraction and the tools Docker provides for working with containers has

changed the system administration and software development landscape. Docker is important

because it makes containers available to everyone. Using it saves time, money, and energy.

The second reason Docker is important is that there is significant push in the software

community to adopt containers and Docker. This push is so strong that companies like

Amazon, Microsoft, and Google have all worked together to contribute to its development and

adopt it in their own cloud offerings. These companies, which are typically at odds, have come

together to support an open source project instead of developing and releasing their own

solutions.

The third reason Docker is important is that it has accomplished for the computer what app

stores did for mobile devices. It has made software installation, compartmentalization, and

removal very simple. Better yet, Docker does it in a cross-platform and open way. Imagine if

all of the major smartphones shared the same app store. That would be a pretty big deal. It’s

possible with this technology in place that the lines between operating systems may finally

start to blur, and third-party offerings will be less of a factor in choosing an operating system.

Fourth, we’re finally starting to see better adoption of some of the more advanced isolation

features of operating systems. This may seem minor, but quite a few people are trying to

make computers more secure through isolation at the operating system level. It’s been a

shame that their hard work has taken so long to see mass adoption. Containers have existed

for decades in one form or another. It’s great that Docker helps us take advantage of those

features without all the complexity.

1.4 Where and when to use Docker

Docker can be used on most computers at work and at home. Practically, how far should this

be taken?

Docker can run almost anywhere, but that doesn’t mean you’ll want to do so. For example,

currently Docker can only run applications that can run on a Linux operating system or

Windows applications on Windows Server. This means that if you want to run an OS X or

Windows native application on your desktop, you can’t yet do so with Docker.

By narrowing the conversation to software that typically runs on a Linux server or desktop,

a solid case can be made for running almost any application inside a container. This includes

server applications like web servers, mail servers, databases, proxies, and the like. Desktop

software like web browsers, word processors, email clients, or other tools are also a great fit.

Even trusted programs are as dangerous to run as a program you downloaded from the

Internet if they interact with user-provided data or network data. Running these in a container

and as a user with reduced privileges will help protect your system from attack.

Beyond the added in-depth benefit of defense, using Docker for day-to-day tasks helps

keep your computer clean. Keeping a clean computer will prevent you from running into

shared resource issues and ease software installation and removal. That same ease of

©Manning Publications Co. We welcome reader comments about anything in the manuscript - other than typos and

other simple mistakes. These will be cleaned up during production of the book by copyeditors and proofreaders.

https://forums.manning.com/forums/docker-in-action-second-edition

Licensed to doreen min <doreenmin127@gmail.com>

installation, removal, and distribution simplifies management of computer fleets and could

radically change the way companies think about maintenance.

The most important thing to remember is when containers are inappropriate. Containers

won’t help much with the security of programs that have to run with full access to the

machine. At the time of this writing, doing so is possible but complicated. Containers are not a

total solution for security issues, but they can be used to prevent many types of attacks.

Remember, you shouldn’t use software from untrusted sources. This is especially true if that

software requires administrative privileges. That means it’s a bad idea to blindly run

customer-provided containers in a collocated environment.

1.5 Docker in the Larger Ecosystem

Today the greater container ecosystem is rich with tooling that solves new or higher-level

problems. Those problems include: container orchestration, high-availability clustering,

microservice life cycle management, and visibility. It can be tricky to navigate that market

without depending on keyword association. It is even trickier to understand how Docker and

those products work together.

Those products work with Docker in the form of plugins or provide some higher-level

functionality and depend on Docker. Some tools use the Docker subcomponents. Those

subcomponents are independent projects like runc, libcontainerd, and notary.

Kubernetes is the most notable project in the ecosystem aside from Docker itself.

Kubernetes provides an extensible platform for orchestrating services as containers in

clustered environments. It is growing into a sort of “datacenter operating system.” Like the

Linux Kernel, cloud providers and platform companies are packaging Kubernetes. Kubernetes

depends on container engines like Docker and so the containers and images you build on your

laptop will run in Kubernetes.

There are several tradeoffs to consider when picking up any tool. Kubernetes draws power

from its extensibility, but that comes at the expense of learning curve and ongoing support

effort. Today building, customizing, or extending Kubernetes clusters is a full-time job. But

using existing Kubernetes clusters to deploy your applications is straightforward with minimal

research. Most readers looking at Kubernetes should consider adopting a managed offering

from a major public cloud provider before building their own. This book focuses on and

teaches solutions to higher-level problems using Docker alone. Once you understand what the

problems are and how to solve them with one tool you’re more likely to succeed in picking up

more complicated tooling.

1.6 Getting help with the Docker command line

You’ll use the docker command-line program throughout the rest of this book. To get you

started with that, I want to show you how to get information about commands from the

docker program itself. This way you’ll understand how to use the exact version of Docker on

your computer. Open a terminal, or command prompt, and run the following command:

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docker help

Running docker help will display information about the basic syntax for using the docker

command-line program as well as a complete list of commands for your version of the

program. Give it a try and take a moment to admire all the neat things you can do.

docker help gives you only high-level information about what commands are available. To

get detailed information about a specific command, include the command in the <COMMAND>

argument. For example, you might enter the following command to find out how to copy files

from a location inside a container to a location on the host machine:

docker help cp

That will display a usage pattern for docker cp, a general description of what the command

does, and a detailed breakdown of its arguments. I’m confident that you’ll have a great time

working through the commands introduced in the rest of this book now that you know how to

find help if you need it.

1.7 Summary

This chapter has been a brief introduction to Docker and the problems it helps system

administrators, developers, and other software users solve. In this chapter you learned that:

• Docker takes a logistical approach to solving common software problems and simplifies

your experience with installing, running, publishing, and removing software. It’s a

command-line program, an engine background process, and a set of remote services.

It’s integrated with community tools provided by Docker Inc.

• The container abstraction is at the core of its logistical approach.

• Working with containers instead of software creates a consistent interface and enables

the development of more sophisticated tools.

• Containers help keep your computers tidy because software inside containers can’t

interact with anything outside those containers, and no shared dependencies can be

formed.

• Because Docker is available and supported on Linux, OS X, and Windows, most

software packaged in Docker images can be used on any computer.

• Docker doesn’t provide container technology; it hides the complexity of working directly

with the container software; and turns best practices into reasonable defaults.

• Docker works with the greater container ecosystem; that ecosystem is rich with tooling

that solves new and higher-level problems.

• If you need help with a command you can always consult the docker help

subcommand.

other simple mistakes. These will be cleaned up during production of the book by copyeditors and proofreaders.

https://forums.manning.com/forums/docker-in-action-second-edition

Licensed to doreen min <doreenmin127@gmail.com>

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