1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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5 | %general-entities;
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6 | ]>
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7 |
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8 | <sect1 id="ch-system-kernfs">
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9 | <?dbhtml filename="kernfs.html"?>
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10 |
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11 | <title>Preparing Virtual Kernel File Systems</title>
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12 |
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13 | <indexterm zone="ch-system-kernfs">
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14 | <primary sortas="e-/dev/">/dev/*</primary>
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15 | </indexterm>
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16 |
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17 | <para>Various file systems exported by the kernel are used to communicate to
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18 | and from the kernel itself. These file systems are virtual in that no disk
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19 | space is used for them. The content of the file systems resides in
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20 | memory.</para>
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21 |
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22 | <para>Begin by creating directories onto which the file systems will be
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23 | mounted:</para>
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24 |
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25 | <screen><userinput>mkdir -pv $LFS/{dev,proc,sys}</userinput></screen>
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26 |
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27 | <sect2>
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28 | <title>Creating Initial Device Nodes</title>
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29 |
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30 | <para>When the kernel boots the system, it requires the presence of a few
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31 | device nodes, in particular the <filename
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32 | class="devicefile">console</filename> and <filename
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33 | class="devicefile">null</filename> devices. The device nodes will be created
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34 | on the hard disk so that they are available before <command>udevd</command>
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35 | has been started, and additionally when Linux is started with
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36 | <parameter>init=/bin/bash</parameter>. Create the devices by running the
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37 | following commands:</para>
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38 |
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39 | <screen><userinput>mknod -m 600 $LFS/dev/console c 5 1
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40 | mknod -m 666 $LFS/dev/null c 1 3</userinput></screen>
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41 |
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42 | </sect2>
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43 |
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44 | <sect2 id="ch-system-bindmount">
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45 | <title>Mounting and Populating /dev</title>
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46 |
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47 | <para>The recommended method of populating the <filename
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48 | class="directory">/dev</filename> directory with devices is to mount a
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49 | virtual filesystem (such as <systemitem
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50 | class="filesystem">tmpfs</systemitem>) on the <filename
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51 | class="directory">/dev</filename> directory, and allow the devices to be
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52 | created dynamically on that virtual filesystem as they are detected or
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53 | accessed. This is generally done during the boot process by Udev. Since
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54 | this new system does not yet have Udev and has not yet been booted, it is
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55 | necessary to mount and populate <filename
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56 | class="directory">/dev</filename> manually. This is accomplished by bind
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57 | mounting the host system's <filename class="directory">/dev</filename>
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58 | directory. A bind mount is a special type of mount that allows you to
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59 | create a mirror of a directory or mount point to some other location. Use
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60 | the following command to achieve this:</para>
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61 |
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62 | <screen><userinput>mount -v --bind /dev $LFS/dev</userinput></screen>
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63 |
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64 | </sect2>
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65 |
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66 | <sect2 id="ch-system-kernfsmount">
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67 | <title>Mounting Virtual Kernel File Systems</title>
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68 |
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69 | <para>Now mount the remaining virtual kernel filesystems:</para>
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70 |
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71 | <screen><userinput>mount -vt devpts devpts $LFS/dev/pts
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72 | mount -vt tmpfs shm $LFS/dev/shm
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73 | mount -vt proc proc $LFS/proc
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74 | mount -vt sysfs sysfs $LFS/sys</userinput></screen>
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75 |
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76 | </sect2>
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77 |
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78 | </sect1>
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