Docker 的前世今生

{"type":"doc","content":[{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"虛擬化"}]},{"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":"要解釋清楚 Docker，首先要解釋清楚容器（Container）的概念"},{"type":"text","text":"。要解釋容器的話，就需要從操作系統說起。操作系統太底層，細說的話一兩本書都說不清楚。這裏就一句話來總結一下：操作系統（Operating System，簡稱OS）是管理計算機硬件與軟件資源的計算機程序，並且爲軟件運行提供通用服務的系統軟件。"}]},{"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":"　　隨着硬件的性能提升，軟件種類的豐富，有兩種情況變得很常見："}]},{"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":"硬件性能過剩——很多計算機的硬件配置，往往會有大量時間處於硬件資源閒置的狀態。例如一般家用電腦，已經是四核、六核的配置了，除了3A遊戲、視頻製作、3D渲染、高性能計算等特殊應用外，通常有 90% 以上時間 CPU 是閒置的；"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"軟件衝突——因爲業務需要，兩個或者多個軟件之間衝突，或者需要同一個軟件的不同版本。例如早幾年做 Web 前端的，要測試網頁在不同版本的 IE 上是否能正常顯示，然而 Windows 只能裝一個版本的 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":"　　爲了解決軟件衝突，只能配置多臺計算機，或者很麻煩的在同一臺電腦上安裝多個操作系統。顯然這兩個方案都有其缺點：多臺計算機成本太高，多操作系統的安裝、切換都很麻煩。在硬件性能過剩的時候，"},{"type":"text","marks":[{"type":"strong"}],"text":"硬件虛擬化"},{"type":"text","text":"的普及就很自然而然的提出來了。"}]},{"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":"　　所謂硬件虛擬化，就是某個特殊的軟件，仿真出一臺或者多臺計算機的各種硬件，用戶可以在這一臺虛擬機上安裝、運行操作系統（一般叫來賓操作系統，Guest OS）和各種應用，並且把 Guest OS 和上面應用軟件對硬件資源的訪問轉發到底層的硬件上來實現。"}]},{"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":"　　對於 Guest OS 和上面的應用程序來說，這臺虛擬機和普通物理計算機是完全一樣沒有任何區別的——除了性能可能差一點。全球第一人氣的 VMware Workstation 就是這麼一個軟件，Oracle 的 VirtualBox 以及 Microsoft 的 Virtual PC 都是。這類軟件英語有一個專用的單詞是 Hypervisor（虛擬機管理程序）。"}]},{"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/96/96c2b53b9c493774f352cb9b95e50520.jpeg","alt":null,"title":"","style":[{"key":"width","value":"100%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"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":3},"content":[{"type":"text","text":"虛擬機的優點"}]},{"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":"　　可以把資源分配到不同的虛擬機，達到硬件資源的最大化利用；"}]},{"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":"　　相比直接在物理機上部署應用，虛擬機更容易擴展應用；"}]},{"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":"　　雲服務：通過虛擬機虛擬出不同的物理資源，可以快速搭建雲服務。"}]},{"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":"虛擬化技術主要用來解決高性能的物理硬件產能過剩和老舊的硬件硬件產品產能過低的重組重用，透明化底層物理硬件，從而最大化的利用物理硬件。"}]}]},{"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":"　　"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"虛擬機的缺點"}]},{"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":"　　虛擬機的缺點在於 Guest OS 通常會佔用不少硬件資源。例如 Windows 安裝 VMware 並開機 Guest OS，不運行任何應用的情況下，就需要佔用 2 ~ 3G 內存，20 ~ 30G 硬盤空間。而且爲了應用系統運行的性能，往往還要給每臺虛擬機留出更多的內存容量。雖然不少 Hypervisor 支持動態內存，但基本上都會降低虛擬機的性能。在這樣的資源佔用情況下，少量的虛擬機還是可以接受的，如果同時運行十多臺或數十臺虛擬機，硬件資源的浪費就會成倍遞增。通常來說，其中相當大一部分甚至全部 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":"　　能不能所有應用使用同一個操作系統減少硬件資源的浪費，但是又能避免包括運行庫在內的軟件衝突呢？"},{"type":"text","marks":[{"type":"strong"}],"text":"操作系統層虛擬化——容器"},{"type":"text","text":"概念的提出，就是爲了解決這個問題。Docker 就是一個容器的標準化實現。"}]},{"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":"　　容器技術已經發展了很長一段時間了，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":"　　容器化就是應用程序級別的虛擬化技術。容器提供了將應用程序的代碼、運行時、系統工具、系統庫和配置打包到一個實例中的標準方法。容器共享一個內核（操作系統），它安裝在硬件上。"}]},{"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":"　　和虛擬機相比，容器有以下優點："}]},{"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":"啓動迅速：沒有虛擬機硬件的初始化，沒有 Guest OS 的啓動過程，可以節約很多啓動時間，這就是容器的“開箱即用”；"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"佔用資源少：沒有運行 Guest OS 所需的內存開銷，無需爲虛擬機預留運行內存，無需安裝、運行 App 不需要的運行庫/操作系統服務，內存佔用、存儲空間佔用都小的多。相同配置的服務器，如果運行虛擬機能運行十多臺的，通常可以運行上百個容器毫無壓力——當然前提是單個容器應用本身不會消耗太多資源。"}]}]}]},{"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 歷史"}]},{"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，幾個搞 IT 的年輕人，在美國舊金山成立了一家名叫 "},{"type":"codeinline","content":[{"type":"text","text":"dotCloud"}]},{"type":"text","text":" 的公司。dotCloud 的平臺即服務（Platform-as-a-Service, PaaS）提供商。底層技術上，dotCloud 平臺利用了 Linux 的 LXC 容器技術。"}]},{"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":"　　爲了方便創建和管理這些容器，dotCloud 基於 Google 公司推出的 Go 語言開發了一套內部工具，之後被命名爲 "},{"type":"codeinline","content":[{"type":"text","text":"Docker"}]},{"type":"text","text":"。Docker 就是這樣誕生的。"}]},{"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 的底層基石，但是在 Docker 0.9 版本的時候，Docker 見異思遷了，引入了基於 Go 語言構建的 Libcontainer 的 execution driver。有了 Libcontainer 這個項目，Docker 不再需要依賴於 Linux 部件（LXC，libvirt，systemd-nspawn...）就可以處理 namespaces、control groups、capabilities、apparmor profiles、network interfaces。這下，LXC 淪爲可選項。"}]}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/87/8744ff14ea3da655e84ffd222b1c82cf.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":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　在 Docker 1.8 中 LXC 被 deprecated，在 Docker 1.10，LXC 徹底出局。Docker 推出 Libcontainer 自己集成了 Linux 內核中的很多特性，作爲一個獨特、穩定且不受制於 Linux 的 Library，獨立的時代終於到來了。"}]}]},{"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 一樣，Docker 的思想來源於集裝箱。集裝箱解決了什麼問題？在一艘大船上，可以把貨物規整的擺放起來，並且各種各樣的貨物被集裝箱標準化，集裝箱與集裝箱之間互不影響。那麼就不需要專門運送水果的船和專門運送化學用品的船了。只要這些貨物封裝在不同的集裝箱裏，就可以用一艘大船把它們都運走。"}]},{"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 技術誕生之後，並沒有引起行業的關注。而 dotCloud 公司，作爲一家小型創業企業，在激烈的競爭之下，也步履維艱。"}]},{"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":"　　正當他們快要堅持不下去的時候，腦子裏蹦出了“開源”的想法。什麼是“開源”？開源，就是開放源代碼。也就是將原來內部保密的程序源代碼開放給所有人，然後讓大家一起參與進來，貢獻代碼和意見。"}]},{"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":"　　有的軟件一開始就是開源的。也有的軟件，是混不下去，創造者又不想放棄，所以選擇開源。自己養不活，就喫“百家飯”嘛。2013 年 3 月，dotCloud 公司的創始人之一，Docker 之父，28 歲的 "},{"type":"text","marks":[{"type":"strong"}],"text":"Solomon Hykes"},{"type":"text","text":" 正式決定，將 Docker 項目開源。"}]},{"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":"image","attrs":{"src":"https://static001.geekbang.org/infoq/11/1150eb88caf3f6ee120aa67a215062d3.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":"　　不開則已，一開驚人。越來越多的 IT 工程師發現了 Docker 的優點，然後蜂擁而至，加入 Docker 開源社區。Docker 的人氣迅速攀升，速度之快，令人瞠目結舌。"}]},{"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":"　　開源當月， Docker 0.1 版本發佈。此後的每一個月， Docker 都會發佈一個版本。到 2014 年 6 月 9 日， Docker 1.0 版本正式發佈。"}]},{"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":"　　此時的 Docker，已經成爲行業里人氣最火爆的開源技術，沒有之一。甚至像 Google、微軟、Amazon、 VMware 這樣的巨頭們都對它青睞有加，表示將全力支持。"}]},{"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 火了之後， dotCloud 公司乾脆把公司名字也改成了 Docker Inc. 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