##Bootstrapping
一：正文
Bootstrapping is the standard term for “starting up a computer” 。The operating system’s normal facilities are not available during the startup process, so the computer must “pull itself up by its own bootstraps.” During bootstrapping,the kernel is loaded into memory and begins to execute. A variety of initialization tasks are performed,and the system is then made available to users.
Boot time is a period of special vulnerability. Errors in configuration,missing or unreliable equipment , and damaged filesystems can all prevent a computer from coming up . Boot configuration is often one of the first tasks an administrator must perform on a new system,especially when adding new hardware.Unfortunately,it is also one of the touchiest. and it requires some familiarity with many other aspects of the system.
When a computer is turned on , it first executes boot code that is stored in ROM.That code in turn attempts to figure out how to load and start the kernel. The kernel probes the system’s hardware and then spawns the system’s init process,which is always process number 1.
Before the system is fully booted,filesystems must be checked and mounted ,and system daemons started. These procedures are managed by a series of shell scripts that are run in sequence by init . The exact layout of the
startup scripts and the manner in which they are executed vary among systems.We cover the details later in this chapter.
二：單詞
*：standard /'stændəd/ 標準
*term /tɜːm/ 術語
*：operating /'ɒpəreɪtɪŋ/ 操作
*：facilities /fə’sɪlɪtɪz/ 工具
*：available /ə’veɪləb(ə)l/ 可獲的的
*：during /'djʊərɪŋ/ 在。。。時候
*：bootstraps 載入程式
*：execute /'eksɪkjuːt/ 執行
*：variety /və’raɪətɪ/ 多樣的
*：initialization /ɪ,nɪʃəlaɪ’zeɪʃən/ 初始化
*：perform /pə’fɔːm/ 執行
*：period /'pɪərɪəd/ 週期
*：vulnerability /,vʌlnərə’bɪlətɪ/ 電腦保安隱患
*：configuration 配置
*：unreliable /ʌnrɪ’laɪəb(ə)l/ 不可依賴的
*：equipment /ɪ’kwɪpm(ə)nt/ 裝置
*：damaged 損壞
*：prevent /prɪ’vent/ 阻止
*：Unfortunately /ʌnˈfɔːtʃənətli/ 不幸的
*：touchiest 敏感的
*：requires 需求
*：attempts 試圖
*：figure out 算出
*：daemons 守護程序
三：全文
引導是啟動計算機的標準說法。作業系統的正常功能在啟動過程中還不能使用，因此，計算機必須用自己的載入程式把自己啟動起來。在引導過程中，核心先被載入到記憶體中，然後開始執行。執行完各種初始化任務以後，使用者就能夠使用系統了。
引導階段是系統最脆弱的一段時間。配置裡有錯誤，找不到裝置或裝置不可靠，還有檔案系統受損都會導致計算機啟動不了。配置系統正常引導經常是系統管理員必須在新系統上做的第一批任務之一。遺憾的是，這也是最困難的任務之一，它要求熟悉Linux的其他許多方面。
計算機開機以後，它先執行儲存在ROM中的引導程式碼。接下來，這段程式碼試著確定如何載入並啟動核心。核心檢測系統的硬體，然後產生系統的init程序，這個程序始終是pid1
系統完全啟動起來之前，先要檢查並掛載檔案系統，並且啟動系統的守護程序。這些步驟由init程序按順序執行的一系列shell指令碼來管理的。啟動指令碼的確切位置佈局，執行方式都隨作業系統的不同而不同。