1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
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3 | "http://www.oasis-open.org/docbook/xml/4.4/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-scripts-network">
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9 | <?dbhtml filename="network.html"?>
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10 |
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11 | <title>Configuring the network Script</title>
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12 |
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13 | <indexterm zone="ch-scripts-network">
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14 | <primary sortas="d-network">network</primary>
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15 | <secondary>configuring</secondary></indexterm>
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16 |
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17 | <para>This section only applies if a network card is to be
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18 | configured.</para>
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19 |
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20 | <para>If a network card will not be used, there is likely no need to
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21 | create any configuration files relating to network cards. If that is
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22 | the case, remove the <filename class="symlink">network</filename>
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23 | symlinks from all run-level directories (<filename
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24 | class="directory">/etc/rc.d/rc*.d</filename>).</para>
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25 |
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26 | <sect2>
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27 | <title>Creating stable names for network interfaces</title>
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28 |
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29 | <para>Instructions in this section are optional if you have only one
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30 | network card.</para>
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31 |
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32 | <para>With Udev and modular network drivers, the network interface numbering
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33 | is not persistent across reboots by default, because the drivers are loaded
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34 | in parallel and, thus, in random order. For example, on a computer having
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35 | two network cards made by Intel and Realtek, the network card manufactured
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36 | by Intel may become <filename class="devicefile">eth0</filename> and the
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37 | Realtek card becomes <filename class="devicefile">eth1</filename>. In some
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38 | cases, after a reboot the cards get renumbered the other way around. To
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39 | avoid this, create Udev rules that assign stable names to network cards
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40 | based on their MAC addresses.</para>
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41 |
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42 | <para>First, find out the MAC addresses of your network cards:</para>
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43 |
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44 | <screen role="nodump"><userinput>grep -H . /sys/class/net/*/address</userinput></screen>
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45 |
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46 | <para>For each network card (but not for the loopback interface),
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47 | invent a descriptive name, such as <quote>realtek</quote>, and create
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48 | Udev rules similar to the following:</para>
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49 |
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50 | <screen role="nodump"><userinput>cat > /etc/udev/rules.d/26-network.rules << "EOF"
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51 | <literal>ACTION=="add", SUBSYSTEM=="net", SYSFS{address}=="<replaceable>52:54:00:12:34:56</replaceable>", NAME="<replaceable>realtek</replaceable>"
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52 | ACTION=="add", SUBSYSTEM=="net", SYSFS{address}=="<replaceable>00:a0:c9:78:9a:bc</replaceable>", NAME="<replaceable>intel</replaceable>"</literal>
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53 | EOF</userinput></screen>
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54 |
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55 | <para>These rules will always rename the network cards to
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56 | <quote>realtek</quote> and <quote>intel</quote>, independently of the
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57 | original numbering provided by the kernel. Use these names instead of
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58 | <quote>eth0</quote> in the network interface configuration files created
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59 | below.</para>
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60 |
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61 | <note>
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62 | <para>Persistent names must be different from the default network
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63 | interface names assigned by the kernel.</para>
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64 | </note>
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65 |
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66 | </sect2>
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67 |
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68 | <sect2>
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69 | <title>Creating Network Interface Configuration Files</title>
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70 |
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71 | <para>Which interfaces are brought up and down by the network script
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72 | depends on the files and directories in the <filename
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73 | class="directory">/etc/sysconfig/network-devices</filename> hierarchy.
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74 | This directory should contain a sub-directory for each interface to be
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75 | configured, such as <filename>ifconfig.xyz</filename>, where
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76 | <quote>xyz</quote> is a network interface name. Inside this directory
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77 | would be files defining the attributes to this interface, such as its IP
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78 | address(es), subnet masks, and so forth.</para>
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79 |
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80 | <para>The following command creates a sample <filename>ipv4</filename>
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81 | file for the <emphasis>eth0</emphasis> device:</para>
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82 |
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83 | <screen><userinput>cd /etc/sysconfig/network-devices &&
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84 | mkdir -v ifconfig.eth0 &&
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85 | cat > ifconfig.eth0/ipv4 << "EOF"
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86 | <literal>ONBOOT=yes
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87 | SERVICE=ipv4-static
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88 | IP=192.168.1.1
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89 | GATEWAY=192.168.1.2
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90 | PREFIX=24
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91 | BROADCAST=192.168.1.255</literal>
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92 | EOF</userinput></screen>
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93 |
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94 | <para>The values of these variables must be changed in every file to match
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95 | the proper setup. If the <envar>ONBOOT</envar> variable is set to
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96 | <quote>yes</quote> the network script will bring up the Network Interface
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97 | Card (NIC) during booting of the system. If set to anything but
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98 | <quote>yes</quote> the NIC will be ignored by the network script and not
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99 | be brought up.</para>
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100 |
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101 | <para>The <envar>SERVICE</envar> variable defines the method used for
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102 | obtaining the IP address. The LFS-Bootscripts package has a modular IP
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103 | assignment format, and creating additional files in the <filename
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104 | class="directory">/etc/sysconfig/network-devices/services</filename>
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105 | directory allows other IP assignment methods. This is commonly used for
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106 | Dynamic Host Configuration Protocol (DHCP), which is addressed in the
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107 | BLFS book.</para>
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108 |
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109 | <para>The <envar>GATEWAY</envar> variable should contain the default
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110 | gateway IP address, if one is present. If not, then comment out the
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111 | variable entirely.</para>
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112 |
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113 | <para>The <envar>PREFIX</envar> variable needs to contain the number of
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114 | bits used in the subnet. Each octet in an IP address is 8 bits. If the
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115 | subnet's netmask is 255.255.255.0, then it is using the first three octets
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116 | (24 bits) to specify the network number. If the netmask is 255.255.255.240,
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117 | it would be using the first 28 bits. Prefixes longer than 24 bits are
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118 | commonly used by DSL and cable-based Internet Service Providers (ISPs).
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119 | In this example (PREFIX=24), the netmask is 255.255.255.0. Adjust the
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120 | <envar>PREFIX</envar> variable according to your specific subnet.</para>
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121 |
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122 | </sect2>
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123 |
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124 | <sect2 id="resolv.conf">
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125 | <title>Creating the /etc/resolv.conf File</title>
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126 |
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127 | <indexterm zone="resolv.conf">
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128 | <primary sortas="e-/etc/resolv.conf">/etc/resolv.conf</primary>
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129 | </indexterm>
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130 |
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131 | <para>If the system is going to be connected to the Internet, it will
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132 | need some means of Domain Name Service (DNS) name resolution to
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133 | resolve Internet domain names to IP addresses, and vice versa. This is
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134 | best achieved by placing the IP address of the DNS server, available
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135 | from the ISP or network administrator, into
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136 | <filename>/etc/resolv.conf</filename>. Create the file by running the
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137 | following:</para>
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138 |
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139 | <screen><userinput>cat > /etc/resolv.conf << "EOF"
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140 | <literal># Begin /etc/resolv.conf
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141 |
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142 | domain {<replaceable><Your Domain Name></replaceable>}
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143 | nameserver <replaceable><IP address of your primary nameserver></replaceable>
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144 | nameserver <replaceable><IP address of your secondary nameserver></replaceable>
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145 |
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146 | # End /etc/resolv.conf</literal>
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147 | EOF</userinput></screen>
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148 |
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149 | <para>Replace <replaceable><IP address of the nameserver></replaceable>
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150 | with the IP address of the DNS most appropriate for the setup. There will
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151 | often be more than one entry (requirements demand secondary servers for
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152 | fallback capability). If you only need or want one DNS server, remove the
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153 | second <emphasis>nameserver</emphasis> line from the file. The IP address
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154 | may also be a router on the local network.</para>
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155 |
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156 | </sect2>
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157 |
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158 | </sect1>
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