Docker 的前世今生

{"type":"doc","content":[{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"虚拟化"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"},{"type":"text","marks":[{"type":"strong"}],"text":"要解释清楚 Docker，首先要解释清楚容器（Container）的概念"},{"type":"text","text":"。要解释容器的话，就需要从操作系统说起。操作系统太底层，细说的话一两本书都说不清楚。这里就一句话来总结一下：操作系统（Operating System，简称OS）是管理计算机硬件与软件资源的计算机程序，并且为软件运行提供通用服务的系统软件。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　随着硬件的性能提升，软件种类的丰富，有两种情况变得很常见："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"numberedlist","attrs":{"start":"1","normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"硬件性能过剩——很多计算机的硬件配置，往往会有大量时间处于硬件资源闲置的状态。例如一般家用电脑，已经是四核、六核的配置了，除了3A游戏、视频制作、3D渲染、高性能计算等特殊应用外，通常有 90% 以上时间 CPU 是闲置的；"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"软件冲突——因为业务需要，两个或者多个软件之间冲突，或者需要同一个软件的不同版本。例如早几年做 Web 前端的，要测试网页在不同版本的 IE 上是否能正常显示，然而 Windows 只能装一个版本的 IE。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　为了解决软件冲突，只能配置多台计算机，或者很麻烦的在同一台电脑上安装多个操作系统。显然这两个方案都有其缺点：多台计算机成本太高，多操作系统的安装、切换都很麻烦。在硬件性能过剩的时候，"},{"type":"text","marks":[{"type":"strong"}],"text":"硬件虚拟化"},{"type":"text","text":"的普及就很自然而然的提出来了。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　所谓硬件虚拟化，就是某个特殊的软件，仿真出一台或者多台计算机的各种硬件，用户可以在这一台虚拟机上安装、运行操作系统（一般叫来宾操作系统，Guest OS）和各种应用，并且把 Guest OS 和上面应用软件对硬件资源的访问转发到底层的硬件上来实现。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　对于 Guest OS 和上面的应用程序来说，这台虚拟机和普通物理计算机是完全一样没有任何区别的——除了性能可能差一点。全球第一人气的 VMware Workstation 就是这么一个软件，Oracle 的 VirtualBox 以及 Microsoft 的 Virtual PC 都是。这类软件英语有一个专用的单词是 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Guest OS 通常会占用不少硬件资源。例如 Windows 安装 VMware 并开机 Guest OS，不运行任何应用的情况下，就需要占用 2 ~ 3G 内存，20 ~ 30G 硬盘空间。而且为了应用系统运行的性能，往往还要给每台虚拟机留出更多的内存容量。虽然不少 Hypervisor 支持动态内存，但基本上都会降低虚拟机的性能。在这样的资源占用情况下，少量的虚拟机还是可以接受的，如果同时运行十多台或数十台虚拟机，硬件资源的浪费就会成倍递增。通常来说，其中相当大一部分甚至全部 Guest OS 都是相同的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　能不能所有应用使用同一个操作系统减少硬件资源的浪费，但是又能避免包括运行库在内的软件冲突呢？"},{"type":"text","marks":[{"type":"strong"}],"text":"操作系统层虚拟化——容器"},{"type":"text","text":"概念的提出，就是为了解决这个问题。Docker 就是一个容器的标准化实现。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"容器化"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　容器技术已经发展了很长一段时间了，例如：LXC，BSD Jails，Solaris Zones..."}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/e4/e46174eb435b5e63439426f359049451.webp","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　容器化就是应用程序级别的虚拟化技术。容器提供了将应用程序的代码、运行时、系统工具、系统库和配置打包到一个实例中的标准方法。容器共享一个内核（操作系统），它安装在硬件上。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/77/7721d08ba43f5dd524459f7d6a7ebc2b.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　和虚拟机相比，容器有以下优点："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"numberedlist","attrs":{"start":"1","normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"启动迅速：没有虚拟机硬件的初始化，没有 Guest OS 的启动过程，可以节约很多启动时间，这就是容器的“开箱即用”；"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"占用资源少：没有运行 Guest OS 所需的内存开销，无需为虚拟机预留运行内存，无需安装、运行 App 不需要的运行库/操作系统服务，内存占用、存储空间占用都小的多。相同配置的服务器，如果运行虚拟机能运行十多台的，通常可以运行上百个容器毫无压力——当然前提是单个容器应用本身不会消耗太多资源。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"Docker 历史"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　2010 年，几个搞 IT 的年轻人，在美国旧金山成立了一家名叫 "},{"type":"codeinline","content":[{"type":"text","text":"dotCloud"}]},{"type":"text","text":" 的公司。dotCloud 的平台即服务（Platform-as-a-Service, PaaS）提供商。底层技术上，dotCloud 平台利用了 Linux 的 LXC 容器技术。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/5b/5b14c45d154f45ebbdf5102d24b7bb51.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　为了方便创建和管理这些容器，dotCloud 基于 Google 公司推出的 Go 语言开发了一套内部工具，之后被命名为 "},{"type":"codeinline","content":[{"type":"text","text":"Docker"}]},{"type":"text","text":"。Docker 就是这样诞生的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　LXC 是 Docker 的底层基石，但是在 Docker 0.9 版本的时候，Docker 见异思迁了，引入了基于 Go 语言构建的 Libcontainer 的 execution driver。有了 Libcontainer 这个项目，Docker 不再需要依赖于 Linux 部件（LXC，libvirt，systemd-nspawn...）就可以处理 namespaces、control groups、capabilities、apparmor profiles、network interfaces。这下，LXC 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Library，独立的时代终于到来了。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/4e/4ec494e9f0e1ccc80bf8055a41060eac.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　如同 Docker 的 Logo 一样，Docker 的思想来源于集装箱。集装箱解决了什么问题？在一艘大船上，可以把货物规整的摆放起来，并且各种各样的货物被集装箱标准化，集装箱与集装箱之间互不影响。那么就不需要专门运送水果的船和专门运送化学用品的船了。只要这些货物封装在不同的集装箱里，就可以用一艘大船把它们都运走。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　Docker 技术诞生之后，并没有引起行业的关注。而 dotCloud 公司，作为一家小型创业企业，在激烈的竞争之下，也步履维艰。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　正当他们快要坚持不下去的时候，脑子里蹦出了“开源”的想法。什么是“开源”？开源，就是开放源代码。也就是将原来内部保密的程序源代码开放给所有人，然后让大家一起参与进来，贡献代码和意见。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　有的软件一开始就是开源的。也有的软件，是混不下去，创造者又不想放弃，所以选择开源。自己养不活，就吃“百家饭”嘛。2013 年 3 月，dotCloud 公司的创始人之一，Docker 之父，28 岁的 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的人气迅速攀升，速度之快，令人瞠目结舌。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　开源当月， Docker 0.1 版本发布。此后的每一个月， Docker 都会发布一个版本。到 2014 年 6 月 9 日， Docker 1.0 版本正式发布。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　此时的 Docker，已经成为行业里人气最火爆的开源技术，没有之一。甚至像 Google、微软、Amazon、 VMware 这样的巨头们都对它青睐有加，表示将全力支持。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　Docker 火了之后， dotCloud 公司干脆把公司名字也改成了 Docker Inc. 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