[519ee45] | 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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[8eb4b13] | 52 | <literal>ACTION=="add", SUBSYSTEM=="net", SYSFS{address}=="<replaceable>00:e0:4c:12:34:56</replaceable>", NAME="<replaceable>realtek</replaceable>"
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| 53 | ACTION=="add", SUBSYSTEM=="net", SYSFS{address}=="<replaceable>00:a0:c9:78:9a:bc</replaceable>", NAME="<replaceable>intel</replaceable>"</literal>
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[519ee45] | 54 | EOF</userinput></screen>
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| 55 |
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| 56 | <!-- Yes, I know that VLANs are beyond BLFS. This is not the reason to get them
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| 57 | incorrect by default when every distro does this right. -->
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| 58 |
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| 59 | <para>If you are going to use the bus position as a key, create
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| 60 | Udev rules similar to the following:</para>
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| 61 |
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| 62 | <screen role="nodump"><userinput>cat > /etc/udev/rules.d/26-network.rules << "EOF"
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| 63 | <literal>ACTION=="add", SUBSYSTEM=="net", BUS=="<replaceable>pci</replaceable>", ID=="<replaceable>0000:00:0c.0</replaceable>", NAME="<replaceable>realtek</replaceable>"
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| 64 | ACTION=="add", SUBSYSTEM=="net", BUS=="<replaceable>pci</replaceable>", ID=="<replaceable>0000:00:0d.0</replaceable>", NAME="<replaceable>intel</replaceable>"</literal>
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| 65 | EOF</userinput></screen>
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| 66 |
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| 67 | <para>These rules will always rename the network cards to
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| 68 | <quote>realtek</quote> and <quote>intel</quote>, independently
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| 69 | of the original numbering provided by the kernel (i.e.: the original
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| 70 | <quote>eth0</quote> and <quote>eth1</quote> interfaces will no longer
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| 71 | exist, unless you put such <quote>descriptive</quote> names in the NAME
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| 72 | key). Use the descriptive names from the Udev rules instead
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| 73 | of <quote>eth0</quote> in the network interface configuration files
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| 74 | below.</para>
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| 75 |
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[8eb4b13] | 76 | <para>Note that the rules above don't work for every setup. For example,
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| 77 | MAC-based rules break when bridges or VLANs are used, because bridges and
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| 78 | VLANs have the same MAC address as the network card. One wants to rename
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| 79 | only the network card interface, not the bridge or VLAN interface, but the
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| 80 | example rule matches both. If you use such virtual interfaces, you have two
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| 81 | potential solutions. One is to add the DRIVER=="?*" key after
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| 82 | SUBSYSTEM=="net" in MAC-based rules which will stop matching the virtual
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| 83 | interfaces. This is known to fail with some older Ethernet cards because
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| 84 | they don't have the DRIVER variable in the uevent and thus the rule does
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| 85 | not match with such cards. Another solution is to switch to rules that use
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| 86 | the bus position as a key.</para>
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| 87 |
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| 88 | <para>The second known non-working case is with wireless cards using the
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| 89 | MadWifi or HostAP drivers, because they create at least two interfaces
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| 90 | with the same MAC address and bus position. For example, the Madwifi driver
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| 91 | creates both an athX and a wifiX interface where X is a digit. To
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| 92 | disambiguate these cases, add SYSFS{type}=="zzz" after SUBSYSTEM=="net" for
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| 93 | each interface that is handled by that driver, where zzz is the output of
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| 94 | <userinput>cat /sys/class/net/<interface_name>/type</userinput>.</para>
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| 95 |
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| 96 | <para>There may be other cases where the rules above don't work. Currently,
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| 97 | bugs on this topic are still being reported to Linux distributions, and no
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| 98 | solution that covers every case is available.</para>
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| 99 |
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[519ee45] | 100 | </sect2>
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| 101 |
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| 102 | <sect2>
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| 103 | <title>Creating Network Interface Configuration Files</title>
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| 104 |
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| 105 | <para>Which interfaces are brought up and down by the network script
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| 106 | depends on the files and directories in the <filename
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| 107 | class="directory">/etc/sysconfig/network-devices</filename> hierarchy.
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| 108 | This directory should contain a sub-directory for each interface to be
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| 109 | configured, such as <filename>ifconfig.xyz</filename>, where
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| 110 | <quote>xyz</quote> is a network interface name. Inside this directory
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| 111 | would be files defining the attributes to this interface, such as its IP
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| 112 | address(es), subnet masks, and so forth.</para>
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| 113 |
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| 114 | <para>The following command creates a sample <filename>ipv4</filename>
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| 115 | file for the <emphasis>eth0</emphasis> device:</para>
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| 116 |
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| 117 | <screen><userinput>cd /etc/sysconfig/network-devices &&
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| 118 | mkdir -v ifconfig.eth0 &&
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| 119 | cat > ifconfig.eth0/ipv4 << "EOF"
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| 120 | <literal>ONBOOT=yes
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| 121 | SERVICE=ipv4-static
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| 122 | IP=192.168.1.1
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| 123 | GATEWAY=192.168.1.2
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| 124 | PREFIX=24
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| 125 | BROADCAST=192.168.1.255</literal>
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| 126 | EOF</userinput></screen>
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| 127 |
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| 128 | <para>The values of these variables must be changed in every file to match
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| 129 | the proper setup. If the <envar>ONBOOT</envar> variable is set to
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| 130 | <quote>yes</quote> the network script will bring up the Network Interface
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| 131 | Card (NIC) during booting of the system. If set to anything but
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| 132 | <quote>yes</quote> the NIC will be ignored by the network script and not
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| 133 | be brought up.</para>
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| 134 |
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| 135 | <para>The <envar>SERVICE</envar> variable defines the method used for
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| 136 | obtaining the IP address. The LFS-Bootscripts package has a modular IP
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| 137 | assignment format, and creating additional files in the <filename
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| 138 | class="directory">/etc/sysconfig/network-devices/services</filename>
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| 139 | directory allows other IP assignment methods. This is commonly used for
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| 140 | Dynamic Host Configuration Protocol (DHCP), which is addressed in the
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| 141 | BLFS book.</para>
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| 142 |
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| 143 | <para>The <envar>GATEWAY</envar> variable should contain the default
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| 144 | gateway IP address, if one is present. If not, then comment out the
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| 145 | variable entirely.</para>
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| 146 |
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| 147 | <para>The <envar>PREFIX</envar> variable needs to contain the number of
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| 148 | bits used in the subnet. Each octet in an IP address is 8 bits. If the
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| 149 | subnet's netmask is 255.255.255.0, then it is using the first three octets
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| 150 | (24 bits) to specify the network number. If the netmask is 255.255.255.240,
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| 151 | it would be using the first 28 bits. Prefixes longer than 24 bits are
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| 152 | commonly used by DSL and cable-based Internet Service Providers (ISPs).
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| 153 | In this example (PREFIX=24), the netmask is 255.255.255.0. Adjust the
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| 154 | <envar>PREFIX</envar> variable according to your specific subnet.</para>
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| 155 |
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| 156 | </sect2>
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| 157 |
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| 158 | <sect2 id="resolv.conf">
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| 159 | <title>Creating the /etc/resolv.conf File</title>
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| 160 |
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| 161 | <indexterm zone="resolv.conf">
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| 162 | <primary sortas="e-/etc/resolv.conf">/etc/resolv.conf</primary>
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| 163 | </indexterm>
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| 164 |
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| 165 | <para>If the system is going to be connected to the Internet, it will
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| 166 | need some means of Domain Name Service (DNS) name resolution to
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| 167 | resolve Internet domain names to IP addresses, and vice versa. This is
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| 168 | best achieved by placing the IP address of the DNS server, available
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| 169 | from the ISP or network administrator, into
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| 170 | <filename>/etc/resolv.conf</filename>. Create the file by running the
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| 171 | following:</para>
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| 172 |
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| 173 | <screen><userinput>cat > /etc/resolv.conf << "EOF"
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| 174 | <literal># Begin /etc/resolv.conf
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| 175 |
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| 176 | domain {<replaceable><Your Domain Name></replaceable>}
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| 177 | nameserver <replaceable><IP address of your primary nameserver></replaceable>
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| 178 | nameserver <replaceable><IP address of your secondary nameserver></replaceable>
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| 179 |
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| 180 | # End /etc/resolv.conf</literal>
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| 181 | EOF</userinput></screen>
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| 182 |
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| 183 | <para>Replace <replaceable><IP address of the nameserver></replaceable>
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| 184 | with the IP address of the DNS most appropriate for the setup. There will
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| 185 | often be more than one entry (requirements demand secondary servers for
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| 186 | fallback capability). If you only need or want one DNS server, remove the
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| 187 | second <emphasis>nameserver</emphasis> line from the file. The IP address
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| 188 | may also be a router on the local network.</para>
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| 189 |
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| 190 | </sect2>
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| 191 |
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| 192 | </sect1>
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