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 or bus positions.</para>
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41 |
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42 | <para>If you are going to use MAC addresses to identify your network
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43 | cards, find the addresses with the following command:</para>
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44 |
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45 | <screen role="nodump"><userinput>grep -H . /sys/class/net/*/address</userinput></screen>
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46 |
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47 | <para>For each network card (but not for the loopback interface),
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48 | invent a descriptive name, such as <quote>realtek</quote>, and create
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49 | Udev rules similar to the following:</para>
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50 |
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51 | <screen role="nodump"><userinput>cat > /etc/udev/rules.d/26-network.rules << "EOF"
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52 | <literal>ACTION=="add", SUBSYSTEM=="net", DRIVER=="?*", SYSFS{address}=="<replaceable>00:e0:4c:12:34:56</replaceable>", NAME="<replaceable>realtek</replaceable>"
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53 | ACTION=="add", SUBSYSTEM=="net", DRIVER=="?*", SYSFS{address}=="<replaceable>00:a0:c9:78:9a:bc</replaceable>", NAME="<replaceable>intel</replaceable>"</literal>
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54 | EOF</userinput></screen>
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55 |
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56 | <para>The DRIVER=="?*" key prevents Udev from attempting to rename 8021Q
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57 | VLAN interfaces (not available without the Vlan package from
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58 | <ulink url="http://www.candelatech.com/~greear/vlan/"/>).
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59 | This is necessary since VLANs have the same MAC address as
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60 | the real network card.</para>
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61 |
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62 | <!-- Yes, I know that VLANs are beyond BLFS. This is not the reason to get them
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63 | incorrect by default when every distro does this right. -->
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64 |
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65 | <para>If you are going to use the bus position as a key, create
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66 | Udev rules similar to the following:</para>
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67 |
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68 | <screen role="nodump"><userinput>cat > /etc/udev/rules.d/26-network.rules << "EOF"
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69 | <literal>ACTION=="add", SUBSYSTEM=="net", BUS=="<replaceable>pci</replaceable>", ID=="<replaceable>0000:00:0c.0</replaceable>", NAME="<replaceable>realtek</replaceable>"
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70 | ACTION=="add", SUBSYSTEM=="net", BUS=="<replaceable>pci</replaceable>", ID=="<replaceable>0000:00:0d.0</replaceable>", NAME="<replaceable>intel</replaceable>"</literal>
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71 | EOF</userinput></screen>
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72 |
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73 | <para>These rules will always rename the network cards to
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74 | <quote>realtek</quote> and <quote>intel</quote>, independently
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75 | of the original numbering provided by the kernel (i.e.: the original
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76 | <quote>eth0</quote> and <quote>eth1</quote> interfaces will no longer
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77 | exist, unless you put such <quote>descriptive</quote> names in the NAME
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78 | key). Use the descriptive names from the Udev rules instead
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79 | of <quote>eth0</quote> in the network interface configuration files
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80 | below.</para>
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81 |
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82 | </sect2>
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83 |
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84 | <sect2>
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85 | <title>Creating Network Interface Configuration Files</title>
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86 |
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87 | <para>Which interfaces are brought up and down by the network script
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88 | depends on the files and directories in the <filename
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89 | class="directory">/etc/sysconfig/network-devices</filename> hierarchy.
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90 | This directory should contain a sub-directory for each interface to be
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91 | configured, such as <filename>ifconfig.xyz</filename>, where
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92 | <quote>xyz</quote> is a network interface name. Inside this directory
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93 | would be files defining the attributes to this interface, such as its IP
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94 | address(es), subnet masks, and so forth.</para>
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95 |
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96 | <para>The following command creates a sample <filename>ipv4</filename>
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97 | file for the <emphasis>eth0</emphasis> device:</para>
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98 |
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99 | <screen><userinput>cd /etc/sysconfig/network-devices &&
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100 | mkdir -v ifconfig.eth0 &&
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101 | cat > ifconfig.eth0/ipv4 << "EOF"
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102 | <literal>ONBOOT=yes
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103 | SERVICE=ipv4-static
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104 | IP=192.168.1.1
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105 | GATEWAY=192.168.1.2
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106 | PREFIX=24
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107 | BROADCAST=192.168.1.255</literal>
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108 | EOF</userinput></screen>
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109 |
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110 | <para>The values of these variables must be changed in every file to match
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111 | the proper setup. If the <envar>ONBOOT</envar> variable is set to
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112 | <quote>yes</quote> the network script will bring up the Network Interface
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113 | Card (NIC) during booting of the system. If set to anything but
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114 | <quote>yes</quote> the NIC will be ignored by the network script and not
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115 | be brought up.</para>
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116 |
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117 | <para>The <envar>SERVICE</envar> variable defines the method used for
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118 | obtaining the IP address. The LFS-Bootscripts package has a modular IP
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119 | assignment format, and creating additional files in the <filename
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120 | class="directory">/etc/sysconfig/network-devices/services</filename>
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121 | directory allows other IP assignment methods. This is commonly used for
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122 | Dynamic Host Configuration Protocol (DHCP), which is addressed in the
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123 | BLFS book.</para>
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124 |
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125 | <para>The <envar>GATEWAY</envar> variable should contain the default
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126 | gateway IP address, if one is present. If not, then comment out the
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127 | variable entirely.</para>
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128 |
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129 | <para>The <envar>PREFIX</envar> variable needs to contain the number of
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130 | bits used in the subnet. Each octet in an IP address is 8 bits. If the
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131 | subnet's netmask is 255.255.255.0, then it is using the first three octets
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132 | (24 bits) to specify the network number. If the netmask is 255.255.255.240,
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133 | it would be using the first 28 bits. Prefixes longer than 24 bits are
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134 | commonly used by DSL and cable-based Internet Service Providers (ISPs).
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135 | In this example (PREFIX=24), the netmask is 255.255.255.0. Adjust the
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136 | <envar>PREFIX</envar> variable according to your specific subnet.</para>
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137 |
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138 | </sect2>
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139 |
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140 | <sect2 id="resolv.conf">
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141 | <title>Creating the /etc/resolv.conf File</title>
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142 |
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143 | <indexterm zone="resolv.conf">
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144 | <primary sortas="e-/etc/resolv.conf">/etc/resolv.conf</primary>
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145 | </indexterm>
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146 |
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147 | <para>If the system is going to be connected to the Internet, it will
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148 | need some means of Domain Name Service (DNS) name resolution to
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149 | resolve Internet domain names to IP addresses, and vice versa. This is
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150 | best achieved by placing the IP address of the DNS server, available
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151 | from the ISP or network administrator, into
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152 | <filename>/etc/resolv.conf</filename>. Create the file by running the
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153 | following:</para>
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154 |
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155 | <screen><userinput>cat > /etc/resolv.conf << "EOF"
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156 | <literal># Begin /etc/resolv.conf
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157 |
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158 | domain {<replaceable><Your Domain Name></replaceable>}
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159 | nameserver <replaceable><IP address of your primary nameserver></replaceable>
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160 | nameserver <replaceable><IP address of your secondary nameserver></replaceable>
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161 |
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162 | # End /etc/resolv.conf</literal>
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163 | EOF</userinput></screen>
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164 |
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165 | <para>Replace <replaceable><IP address of the nameserver></replaceable>
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166 | with the IP address of the DNS most appropriate for the setup. There will
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167 | often be more than one entry (requirements demand secondary servers for
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168 | fallback capability). If you only need or want one DNS server, remove the
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169 | second <emphasis>nameserver</emphasis> line from the file. The IP address
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170 | may also be a router on the local network.</para>
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171 |
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172 | </sect2>
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173 |
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174 | </sect1>
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