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<title>第 3 章 系統初始化</title>
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<th colspan="3" align="center">第 3 章 系統初始化</th>
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<div class="chapter">
<div class="titlepage">
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<div>
<h1 class="title"><a id="_the_system_initialization"/>第 3 章 系統初始化</h1>
</div>
</div>
</div>
<div class="toc">
<p>
<strong>目录</strong>
</p>
<dl class="toc">
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_an_overview_of_the_boot_strap_process">3.1. 啓動過程概述</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_stage_1_the_bios">3.1.1. 第一階段：BIOS</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_stage_2_the_boot_loader">3.1.2. 第二階段：引載加載程序</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_stage_3_the_mini_debian_system">3.1.3. 第三階段：迷你 Debian 系統</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_stage_4_the_normal_debian_system">3.1.4. 第四階段：常規 Debian 系統</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_systemd_init">3.2. Systemd init</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_the_hostname">3.2.1. 主機名</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_the_filesystem">3.2.2. 檔案系統</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_network_interface_initialization">3.2.3. 網路介面初始化</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_the_kernel_message">3.2.4. 核心訊息</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_the_system_message">3.2.5. 系統訊息</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_system_management_under_systemd">3.2.6. System management under systemd</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_customizing_systemd">3.2.7. Customizing systemd</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_the_udev_system">3.3. udev 系統</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="ch03.zh-tw.html#_the_kernel_module_initialization">3.3.1. 核心模組初始化</a>
</span>
</dt>
</dl>
</dd>
</dl>
</div>
<p>作爲系統管理員，粗略地瞭解 Debian
系統的啓動和配置方式是明智的。儘管準確的細節在安裝的軟件包及對應的文檔中，但這些知識對我們大多數人來說都是必須掌握的。</p>
<p>筆者基於自己和其他人的過往及現在的知識，盡己所能地提供關於 Debian 系統的知識要點及其配置的快速概覽作爲讀者的參考。由於 Debian
系統在不斷地更新中，系統的狀況可能已經有所變化。在對系統做任何修改之前，請參考各個軟件包的最新文檔。</p>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p><span class="citerefentry"><span class="refentrytitle">bootup</span>(7)</span>
describes the system bootup process based on <code class="literal">systemd</code>
. (Recent Debian)</p>
</td>
</tr>
</table>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p><span class="citerefentry"><span class="refentrytitle">boot</span>(7)</span>
describes the system bootup process based on UNIX System V Release 4. (Older
Debian)</p>
</td>
</tr>
</table>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="_an_overview_of_the_boot_strap_process"/>3.1. 啓動過程概述</h2>
</div>
</div>
</div>
<p>計算機系統從上電事件到能爲用戶提供完整的操作系統（OS）功能爲止，需要經歷幾個階段的<a class="ulink" href="https://zh.wikipedia.org/wiki/Booting">啓動過程</a>。</p>
<p>爲簡便起見，筆者將討論範圍限定在具有默認安裝的典型 PC 平臺上。</p>
<p>典型的啓動過程像是一個四級的火箭。每一級火箭將系統控制權交給下一級。</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
<a class="xref" href="ch03.zh-tw.html#_stage_1_the_bios" title="3.1.1. 第一階段：BIOS">第 3.1.1 节 “第一階段：BIOS”</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="ch03.zh-tw.html#_stage_2_the_boot_loader" title="3.1.2. 第二階段：引載加載程序">第 3.1.2 节 “第二階段：引載加載程序”</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="ch03.zh-tw.html#_stage_3_the_mini_debian_system" title="3.1.3. 第三階段：迷你 Debian 系統">第 3.1.3 节 “第三階段：迷你 Debian 系統”</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="ch03.zh-tw.html#_stage_4_the_normal_debian_system" title="3.1.4. 第四階段：常規 Debian 系統">第 3.1.4 节 “第四階段：常規 Debian 系統”</a>
</p>
</li>
</ul>
</div>
<p>當然，這些階段可以有不同的配置。比如，你編譯了自己的內核，則可能會跳過迷你 Debian
系統的步驟。因此，在讀者親自確認之前，請勿假定自己系統的情況也是如此。</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[注意]" src="images/note.png"/>
</td>
<th align="left">注意</th>
</tr>
<tr>
<td align="left" valign="top">
<p>對於 SUN 或 Macintosh 系統等非傳統 PC 平臺來說，ROM 上的 BIOS 及磁盤上的分區可能大不相同（<a class="xref" href="ch09.zh-tw.html#_disk_partition_configuration" title="9.5.2. 硬碟分割槽配置">第 9.5.2 节 “硬碟分割槽配置”</a>）。對於這種情況，請另尋對應平臺相關的文檔。</p>
</td>
</tr>
</table>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_stage_1_the_bios"/>3.1.1. 第一階段：BIOS</h3>
</div>
</div>
</div>
<p><a class="ulink" href="https://zh.wikipedia.org/wiki/BIOS">BIOS</a> 是啓動過程的第一階段，在上電事件後開始。CPU
的程序計數器在上電事件後被初始化爲一個特定的內存地址，駐留在<a class="ulink" href="https://zh.wikipedia.org/wiki/Read-only_memory">只讀存儲器（ROM）</a>中的 <a class="ulink" href="https://zh.wikipedia.org/wiki/BIOS">BIOS</a> 就是從這個特定的內存地址開始執行。</p>
<p>BIOS 執行硬件的基本初始化（<a class="ulink" href="https://zh.wikipedia.org/wiki/Power-on_self-test">POST:
上電自檢</a>）並將系統控制權交給你指定的下一步驟。BIOS 通常和硬件一同提供。</p>
<p>BIOS 啓動屏幕通常指示了進入 BIOS 配置界面所需的按鍵。流行的按鍵是 F1、F2、F10、Esc、Ins 和 Del
鍵。假如你的啓動屏幕被一個漂亮的圖形界面隱藏，你可以按下某些按鍵（比如 ESC）取消隱藏。這些按鍵高度依賴於硬件。</p>
<p>硬件位置和 BIOS 啓動的代碼的優先級可以在 BIOS
配置界面中選擇。通常，在已選擇的設備（硬盤、軟件、CD-ROM……）中，最先找到的設備的最開始的幾個扇區將被加載到內存，並執行其中的初始化代碼。初始化代碼可以是以下任意一種。</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
引導加載代碼
</p>
</li>
<li class="listitem">
<p>
類似 <a class="ulink" href="http://www.freedos.org/">FreeDOS</a> 這樣的過濾型操作系統的內核代碼
</p>
</li>
<li class="listitem">
<p>
能夠加載到如此小的空間中的目標操作系統的內核代碼
</p>
</li>
</ul>
</div>
<p>通常，系統從主硬件的特定分區中引導。傳統 PC 硬盤的最開始兩個扇區中包含了<a class="ulink" href="https://zh.wikipedia.org/wiki/Master_boot_record">主引導記錄（MBR）</a>。在 MBR 的末尾記錄了磁盤分區信息及引導選擇。BIOS
中執行的首段引導加載代碼佔據了 MBR 的其餘部分。</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_stage_2_the_boot_loader"/>3.1.2. 第二階段：引載加載程序</h3>
</div>
</div>
</div>
<p><a class="ulink" href="https://zh.wikipedia.org/wiki/Boot_loader">引導加載程序</a>是啓動過程的第二階段，由 BIOS 啓動。引導加載程序將系統內核映像和
<a class="ulink" href="https://zh.wikipedia.org/wiki/Initrd">initrd</a> 映像加載到內存並將控制權交給它們。initrd
映像是根文件系統映像，其支持程度依賴於所使用的引導加載程序。</p>
<p>Debian 系統通常使用 Linux 內核作爲其默認的系統內核。當前 2.6/3.x 版本 Linux 內核的 initrd 映像從技術上說是
initramfs（初始化 RAM 文件系統）映像。initramfs 映像是根文件系統中所有文件的 cpio 歸檔再經過 gzip 壓縮得到。</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Warning">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[警告]" src="images/warning.png"/>
</td>
<th align="left">警告</th>
</tr>
<tr>
<td align="left" valign="top">
<p>使用新的 multi-segment initramfs 之後，上述內容已不正確。請參見<a class="ulink" href="https://bugs.debian.org/790100">錯誤
#790100</a>。</p>
</td>
</tr>
</table>
</div>
<p>Debian 系統默認將 PC 平臺的 GRUB 引導加載程序的第一階段代碼安裝在 <a class="ulink" href="https://zh.wikipedia.org/wiki/Master_boot_record">MBR</a>
中。可用的引導加載程序和配置選項如下。</p>
<div class="table">
<a id="listofbootloaders"/>
<p class="title">
<strong>表 3.1. 引導加載程序列表</strong>
</p>
<div class="table-contents">
<table class="table" summary="引導加載程序列表" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
軟件包
</th>
<th style="text-align: left">
流行度
</th>
<th style="text-align: left">
大小
</th>
<th style="text-align: left">
initrd
</th>
<th style="text-align: left">
引導加載程序
</th>
<th style="text-align: left">
說明
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/grub-legacy"> grub-legacy
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=grub-legacy">V:0, I:2</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/g/grub-legacy.html">710</a>
</td>
<td style="text-align: left">
支持
</td>
<td style="text-align: left">
<a class="ulink" href="https://zh.wikipedia.org/wiki/GNU_GRUB">傳統 GRUB</a>
</td>
<td style="text-align: left">
可智能識別磁盤分區和文件系統（例如 vfat、ext3…）。
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/grub-pc"> grub-pc </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=grub-pc">V:29, I:849</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/g/grub-pc.html">584</a>
</td>
<td style="text-align: left">
支持
</td>
<td style="text-align: left">
<a class="ulink" href="https://zh.wikipedia.org/wiki/GNU_GRUB">GRUB 第 2 版</a>
</td>
<td style="text-align: left">
可智能識別磁盤分區和文件系統（例如 vfat、ext4…）。（默認安裝）
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/grub-rescue-pc"> grub-rescue-pc
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=grub-rescue-pc">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/g/grub-rescue-pc.html">6294</a>
</td>
<td style="text-align: left">
支持
</td>
<td style="text-align: left">
<a class="ulink" href="https://zh.wikipedia.org/wiki/GNU_GRUB">GRUB 第 2 版</a>
</td>
<td style="text-align: left">
此爲 GRUB 第 2 版的可引導修復映像（CD 和軟盤）（PC / BIOS 版本）
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/lilo"> lilo </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=lilo">V:0, I:3</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/l/lilo.html">693</a>
</td>
<td style="text-align: left">
支持
</td>
<td style="text-align: left">
<a class="ulink" href="https://zh.wikipedia.org/wiki/LILO_(boot_loader)">Lilo</a>
</td>
<td style="text-align: left">
依賴於數據在硬盤上的扇區位置。（較老）
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/syslinux"> syslinux </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=syslinux">V:5, I:59</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/syslinux.html">299</a>
</td>
<td style="text-align: left">
支持
</td>
<td style="text-align: left">
<a class="ulink" href="https://zh.wikipedia.org/wiki/SYSLINUX">Isolinux</a>
</td>
<td style="text-align: left">
可識別 ISO9660 文件系統。引導 CD 使用此項。
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/syslinux"> syslinux </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=syslinux">V:5, I:59</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/syslinux.html">299</a>
</td>
<td style="text-align: left">
支持
</td>
<td style="text-align: left">
<a class="ulink" href="https://zh.wikipedia.org/wiki/SYSLINUX">Syslinux</a>
</td>
<td style="text-align: left">
可識別 <a class="ulink" href="https://zh.wikipedia.org/wiki/File_Allocation_Table">MSDOS 文件系統（FAT）</a>。引導軟盤使用此項。
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/loadlin"> loadlin </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=loadlin">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/l/loadlin.html">84</a>
</td>
<td style="text-align: left">
支持
</td>
<td style="text-align: left">
<a class="ulink" href="https://zh.wikipedia.org/wiki/Loadlin">Loadlin</a>
</td>
<td style="text-align: left">
新系統從 FreeDOS 或 MSDOS 中啓動。
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/mbr"> mbr </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=mbr">V:0, I:10</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/m/mbr.html">50</a>
</td>
<td style="text-align: left">
不支持
</td>
<td style="text-align: left">
<a class="ulink" href="http://www.chiark.greenend.org.uk/~neilt/">Neil Turton 的 MBR</a>
</td>
<td style="text-align: left">
此爲取代 MSDOS <a class="ulink" href="https://zh.wikipedia.org/wiki/Master_boot_record">MBR</a> 的自由軟件。只可識別硬盤分區。
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Warning">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[警告]" src="images/warning.png"/>
</td>
<th align="left">警告</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Do not play with boot loaders without having bootable rescue media (USB
memory stick, CD or floppy) created from images in the
<code class="literal">grub-rescue-pc</code> package. It makes you boot your system
even without functioning bootloader on the hard disk.</p>
</td>
</tr>
</table>
</div>
<p>傳統 GRUB 的菜單配置文件位於 <code class="literal">/boot/grub/menu.lst</code>。例如，文件中有如下的配置條目。</p>
<pre class="screen">title Debian GNU/Linux
root (hd0,2)
kernel /vmlinuz root=/dev/hda3 ro
initrd /initrd.img</pre>
<p>GRUB 第 2 版的菜單配置文件位於 <code class="literal">/boot/grub/grub.cfg</code>。此文件由
<code class="literal">/usr/sbin/update-grub</code> 根據
"<code class="literal">/etc/grub.d/*</code>" 中的模板及
"<code class="literal">/etc/default/grub</code>" 中的設置自動生成。例如，文件中有如下的配置條目。</p>
<pre class="screen">menuentry "Debian GNU/Linux" {
set root=(hd0,3)
linux /vmlinuz root=/dev/hda3
initrd /initrd.img
}</pre>
<p>這些示例中，GRUB 參數的含義如下。</p>
<div class="table">
<a id="themeaningofgrubparameters"/>
<p class="title">
<strong>表 3.2. GRUB 參數的含義</strong>
</p>
<div class="table-contents">
<table class="table" summary="GRUB 參數的含義" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
GRUB 參數
</th>
<th style="text-align: left">
說明
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<code class="literal">root</code>
</td>
<td style="text-align: left">
使用主磁盤的第 3 個分區，在傳統 GRUB 中將此參數設置爲 "<code class="literal">(hd0,2)</code>"，在 GRUB 第 2
版中將此參數設置爲 "<code class="literal">(hd0,3)</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">kernel</code>
</td>
<td style="text-align: left">
使用位於 "<code class="literal">/vmlinuz</code>" 的內核，同時將 "<code class="literal">root=/dev/hda3
ro</code>" 作爲參數傳遞給內核
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">initrd</code>
</td>
<td style="text-align: left">
使用 <a class="ulink" href="https://zh.wikipedia.org/wiki/Initrd">initrd/initramfs</a> 映像，其位於
"<code class="literal">/initrd.img</code>"
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[注意]" src="images/note.png"/>
</td>
<th align="left">注意</th>
</tr>
<tr>
<td align="left" valign="top">
<p>傳統 GRUB 使用的分區號爲 Linux 內核及各種實用工具使用的分區號減 1。GRUB 第 2 版修復了這個問題。</p>
</td>
</tr>
</table>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p>在標識一個塊設備時，可能需要使用 <a class="ulink" href="https://zh.wikipedia.org/wiki/Universally_Unique_Identifier">UUID</a>（參見<a class="xref" href="ch09.zh-tw.html#_accessing_partition_using_uuid" title="9.5.3. 使用 UUID 訪問分割槽">第 9.5.3 节 “使用 UUID 訪問分割槽”</a>）而不是類似
"<code class="literal">/dev/hda3</code>" 這樣的文件名，例如
"<code class="literal">root=UUID=81b289d5-4341-4003-9602-e254a17ac232 ro</code>"。</p>
</td>
</tr>
</table>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p>如果使用了 <a class="ulink" href="https://zh.wikipedia.org/wiki/GNU_GRUB">GRUB</a>，內核的啓動參數可以在
<code class="literal">/boot/grub/grub.cfg</code> 裏面設置。在 Debian 系統裏，你不應該直接編輯
<code class="literal">/boot/grub/grub.cfg</code>。你可以通過編輯
<code class="literal">/etc/default/grub</code> 文件中
<code class="literal">GRUB_CMDLINE_LINUX_DEFAULT</code> 的值並運行
<span class="citerefentry"><span class="refentrytitle">update-grub</span>(8)</span>
來更新 <code class="literal">/boot/grub/grub.cfg</code>。</p>
</td>
</tr>
</table>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p>通過使用<a class="ulink" href="https://zh.wikipedia.org/wiki/Chain_loading">鏈式引導</a>技術，你可以在一個引導裝載程序中啓動另一個引導裝載程序。</p>
</td>
</tr>
</table>
</div>
<p>參見 “<code class="literal">info grub</code>” 及
<span class="citerefentry"><span class="refentrytitle">grub-install</span>(8)</span>。</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_stage_3_the_mini_debian_system"/>3.1.3. 第三階段：迷你 Debian 系統</h3>
</div>
</div>
</div>
<p>迷你 Debian 系統是啓動流程的第三階段，由引導加載程序啓動。它會在內存中運行系統內核和根文件系統。這是啓動流程的一個可選準備階段。</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[注意]" src="images/note.png"/>
</td>
<th align="left">注意</th>
</tr>
<tr>
<td align="left" valign="top">
<p>“迷你 Debian 系統”是筆者自創的術語，用於在本文檔中描述啓動流程的第三個階段。這個系統通常被稱爲 <a class="ulink" href="https://zh.wikipedia.org/wiki/Initrd">initrd</a> 或 initramfs 系統。內存中類似的系統在 <a class="ulink" href="https://www.debian.org/devel/debian-installer/">Debian 安裝程序</a>中使用。</p>
</td>
</tr>
</table>
</div>
<p>The "<code class="literal">/init</code>" program is executed as the first program in
this root filesystem on the memory. It is a program which initializes the
kernel in user space and hands control over to the next stage. This
mini-Debian system offers flexibility to the boot process such as adding
kernel modules before the main boot process or mounting the root filesystem
as an encrypted one.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
The "<code class="literal">/init</code>" program is a shell script program if
initramfs was created by <code class="literal">initramfs-tools</code>. <span class="strong"><strong> You can interrupt this part of the boot process to gain root
shell by providing "<code class="literal">break=init</code>" etc. to the kernel boot
parameter. See the "<code class="literal">/init</code>" script for more break
conditions. This shell environment is sophisticated enough to make a good
inspection of your machine's hardware. </strong></span> Commands available in
this mini-Debian system are stripped down ones and mainly provided by a GNU
tool called
<span class="citerefentry"><span class="refentrytitle">busybox</span>(1)</span>.
</p>
</li>
<li class="listitem">
<p>
The "<code class="literal">/init</code>" program is a binary
<code class="literal">systemd</code> program if initramfs was created by
<code class="literal">dracut</code>. ** Commands available in this mini-Debian system
are stripped down
<span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span>
environment.
</p>
</li>
</ul>
</div>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[小心]" src="images/caution.png"/>
</td>
<th align="left">小心</th>
</tr>
<tr>
<td align="left" valign="top">
<p>當在一個只讀的根文件系統上時，使用 <code class="literal">mount</code> 命令需要添加 <code class="literal">-n</code> 選項。</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_stage_4_the_normal_debian_system"/>3.1.4. 第四階段：常規 Debian 系統</h3>
</div>
</div>
</div>
<p>常規 Debian 系統是啓動流程的第四階段，由迷你 Debian 系統啓動。迷你 Debian
系統的內核在此環境下繼續運行。根文件系統將由內存切換到實際的硬盤文件系統上。</p>
<p><a class="ulink" href="https://zh.wikipedia.org/wiki/Init">init</a> 程序是系統執行的第一個程序（PID=1），它啓動其它各種程序以完成主引導流程。init
程序的默認路徑是 ”<code class="literal">/sbin/init</code>“，但可通過內核啓動參數修改，例如
”<code class="literal">init=/path/to/init_program</code>"。</p>
<p>默認的 init 程序一直在變化中：</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
<code class="literal">squeeze</code> 之前的 Debian，使用簡單的 <a class="ulink" href="https://zh.wikipedia.org/wiki/UNIX_System_V">SysV</a>
風格的 init。
</p>
</li>
<li class="listitem">
<p>
<code class="literal">wheezy</code> 版本的 Debian 對 SysV 風格的 init 做了改進：使用 LSB
頭將啓動步驟排序，同時並行執行啓動腳本。
</p>
</li>
<li class="listitem">
<p>
<code class="literal">jessie</code>版本的 Debian 將默認 init 切換成 <a class="ulink" href="https://zh.wikipedia.org/wiki/Systemd">systemd</a>，以使用事件驅動和並行初始化。
</p>
</li>
</ul>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p>你的系統中實際使用的 init 命令可以使用 “<code class="literal">ps --pid 1 -f</code>” 命令確認。</p>
</td>
</tr>
</table>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p>"<code class="literal">/sbin/init</code>" is symlinked to
"<code class="literal">/lib/systemd/systemd</code>" after Debian
<code class="literal">jessie</code>.</p>
</td>
</tr>
</table>
</div>
<div class="table">
<a id="listofbootutilitrthedebiansystem"/>
<p class="title">
<strong>表 3.3. Debian 系統啓動工具列表</strong>
</p>
<div class="table-contents">
<table class="table" summary="Debian 系統啓動工具列表" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
軟件包
</th>
<th style="text-align: left">
流行度
</th>
<th style="text-align: left">
大小
</th>
<th style="text-align: left">
說明
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/systemd">
<code class="literal">systemd</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=systemd">V:703, I:805</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/systemd.html">11933</a>
</td>
<td style="text-align: left">
基於事件且支持並發的
<span class="citerefentry"><span class="refentrytitle">init</span>(8)</span>
守護進程（可替代 <code class="literal">sysvinit</code>）
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/systemd-sysv">
<code class="literal">systemd-sysv</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=systemd-sysv">V:684, I:798</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/systemd-sysv.html">112</a>
</td>
<td style="text-align: left">
the manual pages and links needed for <code class="literal">systemd</code> to replace
<code class="literal">sysvinit</code>
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/systemd-cron">
<code class="literal">systemd-cron</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=systemd-cron">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/systemd-cron.html">133</a>
</td>
<td style="text-align: left"><code class="literal">systemd</code> units to provide <code class="literal">cron</code> daemon
and <code class="literal">anacron</code> functionality
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/init-system-helpers">
<code class="literal">init-system-helpers</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=init-system-helpers">V:704, I:826</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/init-system-helpers.html">129</a>
</td>
<td style="text-align: left">
helper tools for switching between <code class="literal">sysvinit</code> and
<code class="literal">systemd</code>
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/initscripts">
<code class="literal">initscripts</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=initscripts">V:284, I:667</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/initscripts.html">205</a>
</td>
<td style="text-align: left">
用於初始化和關閉系統的腳本
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/sysvinit-core">
<code class="literal">sysvinit-core</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=sysvinit-core">V:13, I:17</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/sysvinit-core.html">225</a>
</td>
<td style="text-align: left">
類 System V 的
<span class="citerefentry"><span class="refentrytitle">init</span>(8)</span>
工具
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/sysv-rc">
<code class="literal">sysv-rc</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=sysv-rc">V:477, I:673</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/sysv-rc.html">123</a>
</td>
<td style="text-align: left">
類 System V 的運行級別修改機制
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/sysvinit-utils">
<code class="literal">sysvinit-utils</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=sysvinit-utils">V:791, I:999</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/sysvinit-utils.html">110</a>
</td>
<td style="text-align: left">
類 System V
的實用工具（<span class="citerefentry"><span class="refentrytitle">startpar</span>(8)</span>，<span class="citerefentry"><span class="refentrytitle">bootlogd</span>(8)</span>，……）
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/lsb-base">
<code class="literal">lsb-base</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=lsb-base">V:877, I:999</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/l/lsb-base.html">49</a>
</td>
<td style="text-align: left"><a class="ulink" href="https://zh.wikipedia.org/wiki/Linux_Standard_Base">Linux 標準規範</a> 3.2 版的 init 腳本功能
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/insserv">
<code class="literal">insserv</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=insserv">V:539, I:660</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/insserv.html">140</a>
</td>
<td style="text-align: left">
利用 LSB init.d 腳本依賴性來組織啓動步驟的工具
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/uswsusp">
<code class="literal">uswsusp</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=uswsusp">V:4, I:11</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/u/uswsusp.html">699</a>
</td>
<td style="text-align: left">
使用 Linux 提供的使用者態軟體 suspend 的工具
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/kexec-tools">
<code class="literal">kexec-tools</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=kexec-tools">V:1, I:8</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/k/kexec-tools.html">270</a>
</td>
<td style="text-align: left">
用於
<span class="citerefentry"><span class="refentrytitle">kexec</span>(8)</span>
重啟（熱啟動）的 kexec 工具
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/systemd-bootchart">
<code class="literal">systemd-bootchart</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=systemd-bootchart">V:0, I:0</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/systemd-bootchart.html">122</a>
</td>
<td style="text-align: left">
啟動流程效能分析器
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/bootchart2">
<code class="literal">bootchart2</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=bootchart2">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/b/bootchart2.html">94</a>
</td>
<td style="text-align: left">
啟動流程效能分析器
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/pybootchartgui">
<code class="literal">pybootchartgui</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=pybootchartgui">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/p/pybootchartgui.html">177</a>
</td>
<td style="text-align: left">
啟動流程效能分析器（視覺化）
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/mingetty">
<code class="literal">mingetty</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=mingetty">V:0, I:3</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/m/mingetty.html">35</a>
</td>
<td style="text-align: left">
僅包含控制檯的
<span class="citerefentry"><span class="refentrytitle">getty</span>(8)</span>
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/mgetty">
<code class="literal">mgetty</code> </a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=mgetty">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/m/mgetty.html">301</a>
</td>
<td style="text-align: left">
可智慧調製解調的
<span class="citerefentry"><span class="refentrytitle">getty</span>(8)</span>
替代品
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p>有關啟動流程加速的最新資訊，請參見 <a class="ulink" href="https://wiki.debian.org/BootProcessSpeedup">Debian
維基：啟動流程加速</a>詞條。</p>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="_systemd_init"/>3.2. Systemd init</h2>
</div>
</div>
</div>
<p>This section describes how system is started by the
<span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span>
program with <code class="literal">PID=1</code> (i.e., init process).</p>
<p>The <code class="literal">systemd</code> init process spawns processes in parallel
based on the unit configuration files (see
<span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span>)
which are written in declarative style instead of SysV-like procedural
style. These are loaded from a set of paths (see
<span class="citerefentry"><span class="refentrytitle">systemd-system.conf</span>(5)</span>)
as follows:</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
"<code class="literal">/lib/systemd/system</code>": OS default configuration files
</p>
</li>
<li class="listitem">
<p>
"<code class="literal">/etc/systemd/system</code>": system administrator configuration
files which override the OS default configuration files
</p>
</li>
<li class="listitem">
<p>
"<code class="literal">/run/systemd/system</code>": run-time generated configuration
files which override the installed configuration files
</p>
</li>
</ul>
</div>
<p>Their inter-dependencies are specified by the directives
"<code class="literal">Wants=</code>", "<code class="literal">Requires=</code>",
"<code class="literal">Before=</code>", "<code class="literal">After=</code>", … (see "MAPPING
OF UNIT PROPERTIES TO THEIR INVERSES" in
<span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span>).
The resource controls are also defined (see
<span class="citerefentry"><span class="refentrytitle">systemd.resource-control</span>(5)</span>).</p>
<p>The suffix of the unit configuration file encodes their types as:</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p><span class="strong"><strong>*.service</strong></span> describes the process
controlled and supervised by <code class="literal">systemd</code>. See
<span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span>.
</p>
</li>
<li class="listitem">
<p><span class="strong"><strong>*.device</strong></span> describes the device exposed in
the
<span class="citerefentry"><span class="refentrytitle">sysfs</span>(5)</span>
as
<span class="citerefentry"><span class="refentrytitle">udev</span>(7)</span>
device tree. See
<span class="citerefentry"><span class="refentrytitle">systemd.device</span>(5)</span>.
</p>
</li>
<li class="listitem">
<p><span class="strong"><strong>*.mount</strong></span> describes the file system mount
point controlled and supervised by <code class="literal">systemd</code>. See
<span class="citerefentry"><span class="refentrytitle">systemd.mount</span>(5)</span>.
</p>
</li>
<li class="listitem">
<p><span class="strong"><strong>*.automount</strong></span> describes the file system
auto mount point controlled and supervised by
<code class="literal">systemd</code>. See
<span class="citerefentry"><span class="refentrytitle">systemd.automount</span>(5)</span>.
</p>
</li>
<li class="listitem">
<p><span class="strong"><strong>*.swap</strong></span> describes the swap device or file
controlled and supervised by <code class="literal">systemd</code>. See
<span class="citerefentry"><span class="refentrytitle">systemd.swap</span>(5)</span>.
</p>
</li>
<li class="listitem">
<p><span class="strong"><strong>*.path</strong></span> describes the path monitored by
<code class="literal">systemd</code> for path-based activation. See
<span class="citerefentry"><span class="refentrytitle">systemd.path</span>(5)</span>.
</p>
</li>
<li class="listitem">
<p><span class="strong"><strong>*.socket</strong></span> describes the socket controlled
and supervised by <code class="literal">systemd</code> for socket-based
activation. See
<span class="citerefentry"><span class="refentrytitle">systemd.socket</span>(5)</span>.
</p>
</li>
<li class="listitem">
<p><span class="strong"><strong>*.timer</strong></span> describes the timer controlled
and supervised by <code class="literal">systemd</code> for timer-based activation. See
<span class="citerefentry"><span class="refentrytitle">systemd.timer</span>(5)</span>.
</p>
</li>
<li class="listitem">
<p><span class="strong"><strong>*.slice</strong></span> manages resources with the
<span class="citerefentry"><span class="refentrytitle">cgroups</span>(7)</span>.
See
<span class="citerefentry"><span class="refentrytitle">systemd.slice</span>(5)</span>.
</p>
</li>
<li class="listitem">
<p><span class="strong"><strong>*.scope</strong></span> is created programmatically using
the bus interfaces of <code class="literal">systemd</code> to manages a set of system
processes. See
<span class="citerefentry"><span class="refentrytitle">systemd.scope</span>(5)</span>.
</p>
</li>
<li class="listitem">
<p><span class="strong"><strong>*.target</strong></span> groups other unit configuration
files to create the synchronization point during start-up. See
<span class="citerefentry"><span class="refentrytitle">systemd.target</span>(5)</span>.
</p>
</li>
</ul>
</div>
<p>Upon system start up (i.e., init), the <code class="literal">systemd</code> process
tries to start the "<code class="literal">/lib/systemd/system/default.target</code>
(normally symlinked to "<code class="literal">graphical.target</code>"). First, some
special target units (see
<span class="citerefentry"><span class="refentrytitle">systemd.special</span>(7)</span>)
such as "<code class="literal">local-fs.target</code>",
"<code class="literal">swap.target</code>" and "<code class="literal">cryptsetup.target</code>"
are pulled in to mount the filesystems. Then, other target units are also
pulled in by the target unit dependencies. For details, read
<span class="citerefentry"><span class="refentrytitle">bootup</span>(7)</span>.</p>
<p><code class="literal">systemd</code> offers backward compatibility features.
SysV-style boot scripts in
"<code class="literal">/etc/init.d/rc[0123456S].d/[KS]<name></code>" are still
parsed and
<span class="citerefentry"><span class="refentrytitle">telinit</span>(8)</span>
is translated into systemd unit activation requests.</p>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[小心]" src="images/caution.png"/>
</td>
<th align="left">小心</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Emulated runlevel 2 to 4 are all symlinked to the same
"<code class="literal">multi-user.target</code>".</p>
</td>
</tr>
</table>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_hostname"/>3.2.1. 主機名</h3>
</div>
</div>
</div>
<p>The kernel maintains the system <span class="strong"><strong>hostname</strong></span>. The system unit started by
<code class="literal">systemd-hostnamed.service</code> sets the system hostname at
boot time to the name stored in "<code class="literal">/etc/hostname</code>". This
file should contain <span class="strong"><strong>only</strong></span> the system
hostname, not a fully qualified domain name.</p>
<p>不帶引數執行
<span class="citerefentry"><span class="refentrytitle">hostname</span>(1)</span>
命令可以打印出當前的主機名。</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_filesystem"/>3.2.2. 檔案系統</h3>
</div>
</div>
</div>
<p>The mount options of normal disk and network filesystems are set in
"<code class="literal">/etc/fstab</code>". See
<span class="citerefentry"><span class="refentrytitle">fstab</span>(5)</span>
and <a class="xref" href="ch09.zh-tw.html#_optimization_of_filesystem_by_mount_options" title="9.5.7. 通過掛載選項優化檔案系統">第 9.5.7 节 “通過掛載選項優化檔案系統”</a>.</p>
<p>The configuration of the encrypted filesystem is set in
"<code class="literal">/etc/crypttab</code>". See
<span class="citerefentry"><span class="refentrytitle">crypttab</span>(5)</span></p>
<p>The configuration of software RAID with
<span class="citerefentry"><span class="refentrytitle">mdadm</span>(8)</span>
is set in "<code class="literal">/etc/mdadm/mdadm.conf</code>". See
<span class="citerefentry"><span class="refentrytitle">mdadm.conf</span>(5)</span>.</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Warning">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[警告]" src="images/warning.png"/>
</td>
<th align="left">警告</th>
</tr>
<tr>
<td align="left" valign="top">
<p>每次啟動的時候，在掛載了所有檔案系統以後，"<code class="literal">/tmp</code>",
"<code class="literal">/var/lock</code>", 和 "<code class="literal">/var/run</code>" 中的臨時檔案會被清空。</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_network_interface_initialization"/>3.2.3. 網路介面初始化</h3>
</div>
</div>
</div>
<p>Network interfaces are typically initialized in
"<code class="literal">networking.service</code>" for the <code class="literal">lo</code>
interface and "<code class="literal">NetworkManager.service</code>" for other
interfaces on modern Debian desktop system under <code class="literal">systemd</code>.</p>
<p>See <a class="xref" href="ch05.zh-tw.html" title="第 5 章 網絡設置">第 5 章 <em>網絡設置</em></a> for how to configure them.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_kernel_message"/>3.2.4. 核心訊息</h3>
</div>
</div>
</div>
<p>The kernel error message displayed to the console can be configured by
setting its threshold level.</p>
<pre class="screen"># dmesg -n3</pre>
<div class="table">
<a id="listofkernelerrorlevels"/>
<p class="title">
<strong>表 3.4. 核心錯誤級別表</strong>
</p>
<div class="table-contents">
<table class="table" summary="核心錯誤級別表" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
錯誤級別值
</th>
<th style="text-align: left">
錯誤級別名稱
</th>
<th style="text-align: left">
說明
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
0
</td>
<td style="text-align: left">
KERN_EMERG
</td>
<td style="text-align: left">
系統不可用
</td>
</tr>
<tr>
<td style="text-align: left">
1
</td>
<td style="text-align: left">
KERN_ALERT
</td>
<td style="text-align: left">
行為必須被立即採取
</td>
</tr>
<tr>
<td style="text-align: left">
2
</td>
<td style="text-align: left">
KERN_CRIT
</td>
<td style="text-align: left">
危險條件
</td>
</tr>
<tr>
<td style="text-align: left">
3
</td>
<td style="text-align: left">
KERN_ERR
</td>
<td style="text-align: left">
錯誤條件
</td>
</tr>
<tr>
<td style="text-align: left">
4
</td>
<td style="text-align: left">
KERN_WARNING
</td>
<td style="text-align: left">
警告條件
</td>
</tr>
<tr>
<td style="text-align: left">
5
</td>
<td style="text-align: left">
KERN_NOTICE
</td>
<td style="text-align: left">
普通但重要的條件
</td>
</tr>
<tr>
<td style="text-align: left">
6
</td>
<td style="text-align: left">
KERN_INFO
</td>
<td style="text-align: left">
資訊提示
</td>
</tr>
<tr>
<td style="text-align: left">
7
</td>
<td style="text-align: left">
KERN_DEBUG
</td>
<td style="text-align: left">
debug 級別的資訊
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_system_message"/>3.2.5. 系統訊息</h3>
</div>
</div>
</div>
<p>Under <code class="literal">systemd</code>, both kernel and system messages are logged
by the journal service <code class="literal">systemd-journald.service</code> (a.k.a
<code class="literal">journald</code>) either into a persistent binary data below
"<code class="literal">/var/log/journal</code>" or into a volatile binary data below
"<code class="literal">/run/log/journal/</code>". These binary log data are accessed
by the
<span class="citerefentry"><span class="refentrytitle">journalctl</span>(1)</span>
command.</p>
<p>Under <code class="literal">systemd</code>, the system logging utility
<span class="citerefentry"><span class="refentrytitle">rsyslogd</span>(8)</span>
changes its behavior to read the volatile binary log data (instead of
pre-systemd default "<code class="literal">/dev/log</code>") and to create traditional
permanent ASCII system log data.</p>
<p>"<code class="literal">/etc/default/rsyslog</code>" 和
"<code class="literal">/etc/rsyslog.conf</code>" 能夠自定義系統訊息的日誌檔案和螢幕顯示。參見
<span class="citerefentry"><span class="refentrytitle">rsyslogd</span>(8)</span>
和
<span class="citerefentry"><span class="refentrytitle">rsyslog.conf</span>(5)</span>，也可以參見<a class="xref" href="ch09.zh-tw.html#_log_analyzer" title="9.2.2. 日誌分析">第 9.2.2 节 “日誌分析”</a>。</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_system_management_under_systemd"/>3.2.6. System management under systemd</h3>
</div>
</div>
</div>
<p>The <code class="literal">systemd</code> offers not only init system but also generic
system management functionalities such as journal logging, login management,
time management, network management. etc..</p>
<p>The
<span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span>
is managed by several commands:</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
the
<span class="citerefentry"><span class="refentrytitle">systemctl</span>(1)</span>
command controls the <code class="literal">systemd</code> system and service manager
(CLI),
</p>
</li>
<li class="listitem">
<p>
the
<span class="citerefentry"><span class="refentrytitle">systemsdm</span>(1)</span>
command controls the <code class="literal">systemd</code> system and service manager
(GUI),
</p>
</li>
<li class="listitem">
<p>
the
<span class="citerefentry"><span class="refentrytitle">journalctl</span>(1)</span>
command queries the <code class="literal">systemd</code> journal,
</p>
</li>
<li class="listitem">
<p>
the
<span class="citerefentry"><span class="refentrytitle">loginctl</span>(1)</span>
command controls the <code class="literal">systemd</code> login manager, and
</p>
</li>
<li class="listitem">
<p>
the
<span class="citerefentry"><span class="refentrytitle">systemd-analyze</span>(1)</span>
analyzes system boot-up performance.
</p>
</li>
</ul>
</div>
<p>Here are a list of typical <code class="literal">systemd</code> management command
snippets. For the exact meanings, please read the pertinent manpages.</p>
<div class="table">
<a id="listoftypicalsystcommandsnippets"/>
<p class="title">
<strong>表 3.5. List of typical <code class="literal">systemd</code> management command snippets</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of typical systemd management command snippets" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
Operation
</th>
<th style="text-align: left">
Type
</th>
<th style="text-align: left">
Command snippets
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
GUI for service manager
</td>
<td style="text-align: left">
GUI
</td>
<td style="text-align: left">
"<code class="literal">systemadm</code>" (<code class="literal">systemd-ui</code> package)
</td>
</tr>
<tr>
<td style="text-align: left">
List all target unit configuration
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl list-units --type=target</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
List all service unit configuration
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl list-units --type=service</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
List all unit configuration types
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl list-units --type=help</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
List all socket units in memory
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl list-sockets</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
List all timer units in memory
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl list-timers</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Start "<code class="literal">$unit</code>"
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl start $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Stop "<code class="literal">$unit</code>"
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl stop $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Reload service-specific configuration
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl reload $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Stop and start all "<code class="literal">$unit</code>"
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl restart $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Start "<code class="literal">$unit</code>" and stop all others
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl isolate $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Switch to "<code class="literal">graphical</code>" (GUI system)
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl isolate graphical</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Switch to "<code class="literal">multi-user</code>" (CLI system)
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl isolate multi-user</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Switch to "<code class="literal">rescue</code>" (single user CLI system)
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl isolate rescue</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Send kill signal to "<code class="literal">$unit</code>"
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl kill $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Send kill signal to "<code class="literal">$unit</code>"
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl kill $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Check if "<code class="literal">$unit</code>" service is active
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl is-active $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Check if "<code class="literal">$unit</code>" service is failed
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl is-failed $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Check status of "<code class="literal">$unit|$PID|device</code>"
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl status $unit|$PID|$device</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Show properties of "<code class="literal">$unit|$job</code>"
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl show $unit|$job</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Reset failed "<code class="literal">$unit</code>"
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl reset-failed $unit"</code>
</td>
</tr>
<tr>
<td style="text-align: left">
List dependency of all unit services
</td>
<td style="text-align: left">
Unit
</td>
<td style="text-align: left">
"<code class="literal">systemctl list-dependencies --all</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
List unit files installed on the system
</td>
<td style="text-align: left">
Unit file
</td>
<td style="text-align: left">
"<code class="literal">systemctl list-unit-files</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Enable "<code class="literal">$unit</code>" (add symlink)
</td>
<td style="text-align: left">
Unit file
</td>
<td style="text-align: left">
"<code class="literal">systemctl enable $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Disable "<code class="literal">$unit</code>" (remove symlink)
</td>
<td style="text-align: left">
Unit file
</td>
<td style="text-align: left">
"<code class="literal">systemctl disable $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Unmask "<code class="literal">$unit</code>" (remove symlink to
"<code class="literal">/dev/null</code>")
</td>
<td style="text-align: left">
Unit file
</td>
<td style="text-align: left">
"<code class="literal">systemctl unmask $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Mask "<code class="literal">$unit</code>" (add symlink to
"<code class="literal">/dev/null</code>")
</td>
<td style="text-align: left">
Unit file
</td>
<td style="text-align: left">
"<code class="literal">systemctl mask $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Get default-target setting
</td>
<td style="text-align: left">
Unit file
</td>
<td style="text-align: left">
"<code class="literal">systemctl get-default</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Set default-target to "<code class="literal">graphical</code>" (GUI system)
</td>
<td style="text-align: left">
Unit file
</td>
<td style="text-align: left">
"<code class="literal">systemctl set-default graphical</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Set default-target to "<code class="literal">multi-user</code>" (CLI system)
</td>
<td style="text-align: left">
Unit file
</td>
<td style="text-align: left">
"<code class="literal">systemctl set-default multi-user</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Show job environment
</td>
<td style="text-align: left">
Environment
</td>
<td style="text-align: left">
"<code class="literal">systemctl show-environment</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Set job environment "<code class="literal">variable</code>" to
"<code class="literal">value</code>"
</td>
<td style="text-align: left">
Environment
</td>
<td style="text-align: left">
"<code class="literal">systemctl set-environment variable=value</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Unset job environment "<code class="literal">variable</code>"
</td>
<td style="text-align: left">
Environment
</td>
<td style="text-align: left">
"<code class="literal">systemctl unset-environment variable</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Reload all unit files and daemons
</td>
<td style="text-align: left">
Lifecycle
</td>
<td style="text-align: left">
"<code class="literal">systemctl daemon-reload</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Shut down the system
</td>
<td style="text-align: left">
System
</td>
<td style="text-align: left">
"<code class="literal">systemctl poweroff</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Shut down and reboot the system
</td>
<td style="text-align: left">
System
</td>
<td style="text-align: left">
"<code class="literal">systemctl reboot</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Suspend the system
</td>
<td style="text-align: left">
System
</td>
<td style="text-align: left">
"<code class="literal">systemctl suspend</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Hibernate the system
</td>
<td style="text-align: left">
System
</td>
<td style="text-align: left">
"<code class="literal">systemctl hibernate</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
View job log of "<code class="literal">$unit</code>"
</td>
<td style="text-align: left">
Journal
</td>
<td style="text-align: left">
"<code class="literal">journalctl -u $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
View job log of "<code class="literal">$unit</code>" ("<code class="literal">tail -f</code>"
style)
</td>
<td style="text-align: left">
Journal
</td>
<td style="text-align: left">
"<code class="literal">journalctl -u $unit -f</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Show time spent for each initialization steps
</td>
<td style="text-align: left">
Analyze
</td>
<td style="text-align: left">
"<code class="literal">systemd-analyze time</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
List of all units by the time to initialize
</td>
<td style="text-align: left">
Analyze
</td>
<td style="text-align: left">
"<code class="literal">systemd-analyze blame</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Load and detect errors in "<code class="literal">$unit</code>" file
</td>
<td style="text-align: left">
Analyze
</td>
<td style="text-align: left">
"<code class="literal">systemd-analyze verify $unit</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Track boot process by the
<span class="citerefentry"><span class="refentrytitle">cgroups</span>(7)</span>
</td>
<td style="text-align: left">
Cgroup
</td>
<td style="text-align: left">
"<code class="literal">systemd-cgls</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Track boot process by the
<span class="citerefentry"><span class="refentrytitle">cgroups</span>(7)</span>
</td>
<td style="text-align: left">
Cgroup
</td>
<td style="text-align: left">
"<code class="literal">ps xawf -eo pid,user,cgroup,args</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
Track boot process by the
<span class="citerefentry"><span class="refentrytitle">cgroups</span>(7)</span>
</td>
<td style="text-align: left">
Cgroup
</td>
<td style="text-align: left">
Read <a class="ulink" href="https://zh.wikipedia.org/wiki/Sysfs">sysfs</a> under
"<code class="literal">/sys/fs/cgroup/systemd/</code>"
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>Here, "<code class="literal">$unit</code>" in the above examples may be a single unit
name (suffix such as <code class="literal">.service</code> and
<code class="literal">.target</code> are optional) or, in many cases, multiple unit
specifications (shell-style globs "<code class="literal">*</code>",
"<code class="literal">?</code>", "<code class="literal">[]</code>" using
<span class="citerefentry"><span class="refentrytitle">fnmatch</span>(3)</span>
which will be matched against the primary names of all units currently in
memory).</p>
<p>System state changing commands in the above examples are typically preceded
by the "<code class="literal">sudo</code>" to attain the required administrative
privilege.</p>
<p>The output of the "<code class="literal">systemctl status $unit|$PID|$device</code>"
uses color of the dot ("●") to summarize the unit state at a glance.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
White "●" indicates an "inactive" or "deactivating" state.
</p>
</li>
<li class="listitem">
<p>
Red "●" indicates a "failed" or "error" state.
</p>
</li>
<li class="listitem">
<p>
Green "●" indicates an "active", "reloading" or "activating" state.
</p>
</li>
</ul>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_customizing_systemd"/>3.2.7. Customizing systemd</h3>
</div>
</div>
</div>
<p>With default installation, many network services (see <a class="xref" href="ch06.zh-tw.html" title="第 6 章 網路應用">第 6 章 <em>網路應用</em></a>) are started as daemon processes after
<code class="literal">network.target</code> at boot time by
<code class="literal">systemd</code>. The "<code class="literal">sshd</code>" is no exception.
Let's change this to on-demand start of "<code class="literal">sshd</code>" as a
customization example.</p>
<p>First, disable system installed service unit.</p>
<pre class="screen"> $ sudo systemctl stop sshd.service
$ sudo systemctl mask sshd.service</pre>
<p>The on-demand socket activation system of the classic Unix services was
through the <code class="literal">indetd</code> superserver. Under
<code class="literal">systemd</code>, the equivalent can be enabled by adding
<span class="strong"><strong>*.socket</strong></span> and <span class="strong"><strong>*.service</strong></span> unit configuration files.</p>
<p><code class="literal">sshd.socket</code> for specifying a socket to listen on</p>
<pre class="screen">[Unit]
Description=SSH Socket for Per-Connection Servers
[Socket]
ListenStream=22
Accept=yes
[Install]
WantedBy=sockets.target</pre>
<p><code class="literal">sshd@.service</code> as the matching service file of
<code class="literal">sshd.socket</code></p>
<pre class="screen">[Unit]
Description=SSH Per-Connection Server
[Service]
ExecStart=-/usr/sbin/sshd -i
StandardInput=socket</pre>
<p>Then reload.</p>
<pre class="screen"> $ sudo systemctl daemon-reload</pre>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="_the_udev_system"/>3.3. udev 系統</h2>
</div>
</div>
</div>
<p>Linux 核心 2.6 和更新的核心，<a class="ulink" href="https://zh.wikipedia.org/wiki/Udev">udev 系統</a>
提供了自動硬體發現和初始化機制。(參見
<span class="citerefentry"><span class="refentrytitle">udev</span>(7)</span>).在核心發現每個裝置的基礎上，udev
系統使用從 <a class="ulink" href="https://zh.wikipedia.org/wiki/Sysfs">sysfs</a> 檔案系統 (參見 <a class="xref" href="ch01.zh-tw.html#_procfs_and_sysfs" title="1.2.12. procfs 和 sysfs">第 1.2.12 节 “procfs 和 sysfs”</a>)的資訊啟動一個使用者程序，使用
<span class="citerefentry"><span class="refentrytitle">modprobe</span>(8)</span>
程式 (參見 <a class="xref" href="ch03.zh-tw.html#_the_kernel_module_initialization" title="3.3.1. 核心模組初始化">第 3.3.1 节 “核心模組初始化”</a>)載入支援它所要求的核心模組,
建立相應的裝置節點。</p>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p>如果由於某些理由，"<code class="literal">/lib/modules/<kernel-version>/modules.dep</code>"沒有被
<span class="citerefentry"><span class="refentrytitle">depmod</span>(8)</span>
正常生成，模組可能不會被 udev 系統按期望的方式載入。執行"<code class="literal">depmod -a</code>" 來修復它。</p>
</td>
</tr>
</table>
</div>
<p>裝置節點的名字，可以通過"<code class="literal">/etc/udev/rules.d/</code>"裡的 udev
檔案來配置.當前預設的規則傾向建立動態生成的名字，除了光碟機和網路裝置外，會生成非靜態的裝置名。通過新增和光碟機、網路裝置類似的個性化規則，你也可以為
USB 盤之類的其它裝置，生成靜態裝置名。 參見 "<a class="ulink" href="http://www.reactivated.net/writing_udev_rules.html">Writing udev
rules</a>" 或
"<code class="literal">/usr/share/doc/udev/writing_udev_rules/index.html</code>".</p>
<p>由於 udev 系統是一個正在變化的事物，我在其它文件進行了詳細描述，在這裡只提供了最少的資訊。</p>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p>"<code class="literal">/etc/fstab</code>"裡面的掛載規則,裝置節點不必需是靜態的。你能夠使用 <a class="ulink" href="https://zh.wikipedia.org/wiki/Universally_Unique_Identifier">UUID</a> 來掛載裝置，來代替"<code class="literal">/dev/sda</code>"之類的裝置名. 參見
<a class="xref" href="ch09.zh-tw.html#_accessing_partition_using_uuid" title="9.5.3. 使用 UUID 訪問分割槽">第 9.5.3 节 “使用 UUID 訪問分割槽”</a>.</p>
</td>
</tr>
</table>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_kernel_module_initialization"/>3.3.1. 核心模組初始化</h3>
</div>
</div>
</div>
<p>通過
<span class="citerefentry"><span class="refentrytitle">modprobe</span>(8)</span>
程式新增和刪除核心模組，使我們能夠從使用者程序來配置正在執行的 Linux 核心。udev 系統(參見 <a class="xref" href="ch03.zh-tw.html#_the_udev_system" title="3.3. udev 系統">第 3.3 节 “udev 系統”</a>)自動化它的呼叫來幫助核心模組初始化。</p>
<p>下面的非硬體模組和特殊的硬體驅動模組，需要被預先載入，把它們在"<code class="literal">/etc/modules</code>"檔案裡列出 (參見
<span class="citerefentry"><span class="refentrytitle">modules</span>(5)</span>).</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p><a class="ulink" href="https://zh.wikipedia.org/wiki/TUN/TAP">TUN/TAP</a> 模組提供虛擬的 Point-to-Point 網路裝置 (TUN) 和虛擬的
Ethernet 乙太網網路裝置 (TAP),
</p>
</li>
<li class="listitem">
<p><a class="ulink" href="https://zh.wikipedia.org/wiki/Netfilter">netfilter</a> 模組提供 netfilter
防火牆能力(<span class="citerefentry"><span class="refentrytitle">iptables</span>(8)</span>,
<a class="xref" href="ch05.zh-tw.html#_netfilter_infrastructure" title="5.10. Netfilter 網路過濾框架">第 5.10 节 “Netfilter 網路過濾框架”</a>),
</p>
</li>
<li class="listitem">
<p><a class="ulink" href="https://zh.wikipedia.org/wiki/Watchdog_timer">watchdog timer</a> 驅動模組。
</p>
</li>
</ul>
</div>
<p><span class="citerefentry"><span class="refentrytitle">modprobe</span>(8)</span>
程式的配置檔案是按
<span class="citerefentry"><span class="refentrytitle">modprobe.conf</span>(5)</span>的說明放在"<code class="literal">/etc/modprobes.d/</code>"
目錄下，(如果你想避免自動載入某些核心模組，考慮把它們作為黑名單放在"<code class="literal">/etc/modprobes.d/blacklist</code>"
檔案裡.)</p>
<p>"<code class="literal">/lib/modules/<version>/modules.dep</code>" 檔案由
<span class="citerefentry"><span class="refentrytitle">depmod</span>(8)</span>
程式生成，它描述了
<span class="citerefentry"><span class="refentrytitle">modprobe</span>(8)</span>
程式使用的模組依賴性.</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[注意]" src="images/note.png"/>
</td>
<th align="left">注意</th>
</tr>
<tr>
<td align="left" valign="top">
<p>如果你在啟動時出現模組載入問題，或者
<span class="citerefentry"><span class="refentrytitle">modprobe</span>(8)</span>時出現模組載入問題,
"<code class="literal">depmod -a</code>"
可以通過重構"<code class="literal">modules.dep</code>"來解決這些問題。</p>
</td>
</tr>
</table>
</div>
<p><span class="citerefentry"><span class="refentrytitle">modinfo</span>(8)</span>
程式顯示 Linux 核心模組資訊。</p>
<p><span class="citerefentry"><span class="refentrytitle">lsmod</span>(8)</span>
程式以好看的格式展示"<code class="literal">/proc/modules</code>"的內容,顯示當前核心載入了哪些模組。</p>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p>你能夠精確識別你係統上的硬體。 參見<a class="xref" href="ch09.zh-tw.html#_hardware_identification" title="9.4.3. 硬體識別">第 9.4.3 节 “硬體識別”</a>.</p>
</td>
</tr>
</table>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p>你可以在啟動時配置硬體來啟用期望的硬體特徵。參見 <a class="xref" href="ch09.zh-tw.html#_hardware_configuration" title="9.4.4. 硬體配置">第 9.4.4 节 “硬體配置”</a>.</p>
</td>
</tr>
</table>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[提示]" src="images/tip.png"/>
</td>
<th align="left">提示</th>
</tr>
<tr>
<td align="left" valign="top">
<p>你可以重新編譯核心來增加你的特殊裝置的支援。參見 <a class="xref" href="ch09.zh-tw.html#_the_kernel" title="9.9. 核心">第 9.9 节 “核心”</a>.</p>
</td>
</tr>
</table>
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