[673b0d8] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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[d781ffb] | 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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[673b0d8] | 4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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| 5 | %general-entities;
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| 6 | ]>
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[d781ffb] | 7 |
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[3be4d97] | 8 | <sect1 id="ch-scripts-network">
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[d781ffb] | 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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[d2c332bc] | 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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[966b175] | 40 | based on their MAC addresses or bus positions.</para>
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[d2c332bc] | 41 |
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[966b175] | 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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[d2c332bc] | 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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[ac3fb3e9] | 51 | <screen role="nodump"><userinput>cat > /etc/udev/rules.d/70-persistent-net.rules << EOF
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[c226182] | 52 | <literal>ACTION=="add", SUBSYSTEM=="net", SYSFS{address}=="<replaceable>00:e0:4c:12:34:56</replaceable>", \
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| 53 | NAME="<replaceable>realtek</replaceable>"
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| 54 | ACTION=="add", SUBSYSTEM=="net", SYSFS{address}=="<replaceable>00:a0:c9:78:9a:bc</replaceable>", \
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| 55 | NAME="<replaceable>intel</replaceable>"</literal>
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[966b175] | 56 | EOF</userinput></screen>
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| 57 |
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| 58 | <!-- Yes, I know that VLANs are beyond BLFS. This is not the reason to get them
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| 59 | incorrect by default when every distro does this right. -->
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[c226182] | 60 |
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| 61 | <note>
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[d0d8dc8] | 62 | <para>Be aware that Udev does not recognize the backslash for line
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| 63 | continuation. The examples in this book work properly because both
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| 64 | the backslash and newline are ignored by the shell. This makes the
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| 65 | shell send each rule to cat on only one line. (The shell ignores
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| 66 | this sequence because the EOF string used in the here-document
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| 67 | redirection is not enclosed in either double or single quotes. For
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| 68 | more details, see the bash(1) manpage, and search it for "Here
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| 69 | Documents".)</para>
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| 70 | <para>If modifying Udev rules with an editor, be sure to leave each
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| 71 | rule on one physical line.</para>
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[c226182] | 72 | </note>
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| 73 |
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[a804834] | 74 | <para>If you are going to use the bus position as the key, find the
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| 75 | position of each card with the following commands:</para>
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| 76 |
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| 77 | <screen role="nodump"><userinput>for dir in /sys/class/net/* ; do
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| 78 | [ -e $dir/device ] && {
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| 79 | basename $dir ; readlink -f $dir/device
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| 80 | }
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| 81 | done</userinput></screen>
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| 82 |
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| 83 | <para>This will yield output similar to:</para>
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| 84 |
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| 85 | <screen role="nodump"><userinput><replaceable>eth0</replaceable>
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| 86 | /sys/devices/pci0000:00/<replaceable>0000:00:0c.0</replaceable>
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| 87 | <replaceable>eth1</replaceable>
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| 88 | /sys/devices/pci0000:00/<replaceable>0000:00:0d.0</replaceable></userinput></screen>
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| 89 |
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| 90 | <para>In this example, <replaceable>eth0</replaceable> has PCI bus position
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| 91 | <replaceable>0000:00:0c.0</replaceable> (domain 0000, bus 00, device 0c,
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| 92 | function 0), and <replaceable>eth1</replaceable> has PCI bus position
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| 93 | <replaceable>0000:00:0d.0</replaceable> (domain 0000, bus 00, device 0d,
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| 94 | function 0).</para>
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| 95 |
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| 96 | <para>Now create Udev rules similar to the following:</para>
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[966b175] | 97 |
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[ac3fb3e9] | 98 | <screen role="nodump"><userinput>cat > /etc/udev/rules.d/70-persistent-net.rules << EOF
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[a804834] | 99 | <literal>ACTION=="add", SUBSYSTEM=="net", BUS=="<replaceable>pci</replaceable>", KERNELS=="<replaceable>0000:00:0c.0</replaceable>", \
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[c226182] | 100 | NAME="<replaceable>realtek</replaceable>"
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[a804834] | 101 | ACTION=="add", SUBSYSTEM=="net", BUS=="<replaceable>pci</replaceable>", KERNELS=="<replaceable>0000:00:0d.0</replaceable>", \
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[c226182] | 102 | NAME="<replaceable>intel</replaceable>"</literal>
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[d2c332bc] | 103 | EOF</userinput></screen>
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| 104 |
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[97c1e3ce] | 105 | <para>Udev has installed a rule_generator rules file that uses MAC
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| 106 | addresses, not bus positions. Rules generated by this file will conflict
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| 107 | with the rules you just created, so delete the file:</para>
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| 108 |
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| 109 | <screen role="nodump"><userinput>rm /etc/udev/rules.d/75-persistent-net-generator.rules</userinput></screen>
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| 110 |
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| 111 | <note>
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| 112 | <para>You will also have to remember to create a new bus-position-based
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| 113 | rule each time you plug in an additional network card. In a MAC address
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| 114 | based persistence scheme, the rule_generator rules file would do this
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| 115 | automatically.</para>
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| 116 | </note>
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| 117 |
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[a804834] | 118 | <para>Regardless of which method you use, these rules will always rename
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| 119 | the network cards to <quote>realtek</quote> and <quote>intel</quote>,
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| 120 | independently of the original numbering provided by the kernel (i.e.: the
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| 121 | original <quote>eth0</quote> and <quote>eth1</quote> interfaces will no
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| 122 | longer exist, unless you put such <quote>descriptive</quote> names in the
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| 123 | NAME key). Use the descriptive names from the Udev rules instead of
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| 124 | <quote>eth0</quote> in the network interface configuration files
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[d2c332bc] | 125 | below.</para>
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| 126 |
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[c226182] | 127 | <para>Note that the rules above don't work for every setup. For example,
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| 128 | MAC-based rules break when bridges or VLANs are used, because bridges and
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| 129 | VLANs have the same MAC address as the network card. One wants to rename
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| 130 | only the network card interface, not the bridge or VLAN interface, but the
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| 131 | example rule matches both. If you use such virtual interfaces, you have two
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| 132 | potential solutions. One is to add the DRIVER=="?*" key after
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| 133 | SUBSYSTEM=="net" in MAC-based rules which will stop matching the virtual
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| 134 | interfaces. This is known to fail with some older Ethernet cards because
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| 135 | they don't have the DRIVER variable in the uevent and thus the rule does
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| 136 | not match with such cards. Another solution is to switch to rules that use
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| 137 | the bus position as a key.</para>
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| 138 |
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| 139 | <para>The second known non-working case is with wireless cards using the
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| 140 | MadWifi or HostAP drivers, because they create at least two interfaces with
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| 141 | the same MAC address and bus position. For example, the Madwifi driver
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| 142 | creates both an athX and a wifiX interface where X is a digit. To
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| 143 | differentiate these interfaces, add an appropriate KERNEL parameter such as
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| 144 | KERNEL=="ath*" after SUBSYSTEM=="net".</para>
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| 145 |
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| 146 | <para>There may be other cases where the rules above don't work. Currently,
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| 147 | bugs on this topic are still being reported to Linux distributions, and no
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| 148 | solution that covers every case is available.</para>
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| 149 |
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[d2c332bc] | 150 | </sect2>
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| 151 |
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[d781ffb] | 152 | <sect2>
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| 153 | <title>Creating Network Interface Configuration Files</title>
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| 154 |
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| 155 | <para>Which interfaces are brought up and down by the network script
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| 156 | depends on the files and directories in the <filename
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| 157 | class="directory">/etc/sysconfig/network-devices</filename> hierarchy.
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| 158 | This directory should contain a sub-directory for each interface to be
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| 159 | configured, such as <filename>ifconfig.xyz</filename>, where
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| 160 | <quote>xyz</quote> is a network interface name. Inside this directory
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| 161 | would be files defining the attributes to this interface, such as its IP
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| 162 | address(es), subnet masks, and so forth.</para>
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| 163 |
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| 164 | <para>The following command creates a sample <filename>ipv4</filename>
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| 165 | file for the <emphasis>eth0</emphasis> device:</para>
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[00a2bd12] | 166 |
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[a088964] | 167 | <screen><userinput>cd /etc/sysconfig/network-devices &&
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[5998892] | 168 | mkdir -v ifconfig.eth0 &&
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[a088964] | 169 | cat > ifconfig.eth0/ipv4 << "EOF"
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[d72e04a] | 170 | <literal>ONBOOT=yes
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[a088964] | 171 | SERVICE=ipv4-static
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[00a2bd12] | 172 | IP=192.168.1.1
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[ba85054d] | 173 | GATEWAY=192.168.1.2
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[c0155c7] | 174 | PREFIX=24
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[d72e04a] | 175 | BROADCAST=192.168.1.255</literal>
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[f67f5cf] | 176 | EOF</userinput></screen>
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[00a2bd12] | 177 |
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[d781ffb] | 178 | <para>The values of these variables must be changed in every file to match
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| 179 | the proper setup. If the <envar>ONBOOT</envar> variable is set to
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| 180 | <quote>yes</quote> the network script will bring up the Network Interface
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| 181 | Card (NIC) during booting of the system. If set to anything but
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| 182 | <quote>yes</quote> the NIC will be ignored by the network script and not
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| 183 | be brought up.</para>
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| 184 |
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| 185 | <para>The <envar>SERVICE</envar> variable defines the method used for
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| 186 | obtaining the IP address. The LFS-Bootscripts package has a modular IP
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| 187 | assignment format, and creating additional files in the <filename
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| 188 | class="directory">/etc/sysconfig/network-devices/services</filename>
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| 189 | directory allows other IP assignment methods. This is commonly used for
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| 190 | Dynamic Host Configuration Protocol (DHCP), which is addressed in the
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| 191 | BLFS book.</para>
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| 192 |
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| 193 | <para>The <envar>GATEWAY</envar> variable should contain the default
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| 194 | gateway IP address, if one is present. If not, then comment out the
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| 195 | variable entirely.</para>
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| 196 |
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| 197 | <para>The <envar>PREFIX</envar> variable needs to contain the number of
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| 198 | bits used in the subnet. Each octet in an IP address is 8 bits. If the
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| 199 | subnet's netmask is 255.255.255.0, then it is using the first three octets
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| 200 | (24 bits) to specify the network number. If the netmask is 255.255.255.240,
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| 201 | it would be using the first 28 bits. Prefixes longer than 24 bits are
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| 202 | commonly used by DSL and cable-based Internet Service Providers (ISPs).
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| 203 | In this example (PREFIX=24), the netmask is 255.255.255.0. Adjust the
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| 204 | <envar>PREFIX</envar> variable according to your specific subnet.</para>
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| 205 |
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| 206 | </sect2>
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| 207 |
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| 208 | <sect2 id="resolv.conf">
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| 209 | <title>Creating the /etc/resolv.conf File</title>
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| 210 |
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| 211 | <indexterm zone="resolv.conf">
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| 212 | <primary sortas="e-/etc/resolv.conf">/etc/resolv.conf</primary>
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| 213 | </indexterm>
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| 214 |
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| 215 | <para>If the system is going to be connected to the Internet, it will
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| 216 | need some means of Domain Name Service (DNS) name resolution to
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| 217 | resolve Internet domain names to IP addresses, and vice versa. This is
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| 218 | best achieved by placing the IP address of the DNS server, available
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| 219 | from the ISP or network administrator, into
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| 220 | <filename>/etc/resolv.conf</filename>. Create the file by running the
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| 221 | following:</para>
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[45340ae] | 222 |
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[f67f5cf] | 223 | <screen><userinput>cat > /etc/resolv.conf << "EOF"
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[d72e04a] | 224 | <literal># Begin /etc/resolv.conf
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[45340ae] | 225 |
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[4b51ca76] | 226 | domain <replaceable><Your Domain Name></replaceable>
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[0090db5] | 227 | nameserver <replaceable><IP address of your primary nameserver></replaceable>
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| 228 | nameserver <replaceable><IP address of your secondary nameserver></replaceable>
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[45340ae] | 229 |
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[d72e04a] | 230 | # End /etc/resolv.conf</literal>
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[f67f5cf] | 231 | EOF</userinput></screen>
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[45340ae] | 232 |
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[0090db5] | 233 | <para>Replace <replaceable><IP address of the nameserver></replaceable>
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[d781ffb] | 234 | with the IP address of the DNS most appropriate for the setup. There will
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| 235 | often be more than one entry (requirements demand secondary servers for
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| 236 | fallback capability). If you only need or want one DNS server, remove the
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| 237 | second <emphasis>nameserver</emphasis> line from the file. The IP address
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| 238 | may also be a router on the local network.</para>
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[45340ae] | 239 |
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[d781ffb] | 240 | </sect2>
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[81fd230] | 241 |
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[d781ffb] | 242 | </sect1>
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