source: chapter07/network.xml@ 4f61f8f

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<sect1 id="ch-scripts-network">
<title>Configuring the network Script</title>
<?dbhtml filename="network.html"?>

<indexterm zone="ch-scripts-network">
<primary sortas="d-network">network</primary>
<secondary>configuring</secondary></indexterm>

<para>This section only applies if a network card is to be
configured.</para>

<para>If a network card will not be used, there is likely no need to
create any configuration files relating to network cards. If that is
the case, remove the <filename class="symlink">network</filename>
symlinks from all run-level directories (<filename
class="directory">/etc/rc.d/rc*.d</filename>).</para>

<sect2>
<title>Creating Network Interface Configuration Files</title>

<para>Which interfaces are brought up and down by the network script
depends on the files in the <filename
class="directory">/etc/sysconfig/network-devices</filename> directory.
This directory should contain files in the form of
<filename>ifconfig.xyz</filename>, where <quote>xyz</quote> is a
network interface name (such as eth0 or eth0:1).</para>

<para>If the <filename
class="directory">/etc/sysconfig/network-devices</filename> directory
is to be renamed or moved, make sure to edit the
<filename>/etc/sysconfig/rc</filename> file and update the
<quote>network_devices</quote> option by providing it with the new
path.</para>

<para>New files are created in this directory. The following
command creates a sample <filename>ipv4</filename> file for the
<emphasis>eth0</emphasis> device:</para>

<screen><userinput>cd /etc/sysconfig/network-devices &amp;&amp;
mkdir ifconfig.eth0 &amp;&amp;
cat &gt; ifconfig.eth0/ipv4 &lt;&lt; "EOF"
<literal>ONBOOT=yes
SERVICE=ipv4-static
IP=192.168.1.1
GATEWAY=192.168.1.2
PREFIX=24
BROADCAST=192.168.1.255</literal>
EOF</userinput></screen>

<para>The values of these variables must be changed in every file to
match the proper setup. If the <envar>ONBOOT</envar> variable is
set to <quote>yes</quote> the network script will bring up the
Network Interface Card (NIC) during booting of the system. If set
to anything but <quote>yes</quote> the NIC will be ignored by the
network script and not brought up.</para>

<para>The <envar>SERVICE</envar> variable defines the method of
obtaining the IP address. The LFS bootscripts have a modular IP
assignment format, and creating additional files in the <filename
class="directory">/etc/sysconfig/network-devices/services</filename>
directory allows other IP assignment methods. This is commonly used
for Dynamic Host Configuration Protocol (DHCP), which is addressed in the BLFS book.</para>

<para>The <envar>GATEWAY</envar> variable should contain
the default gateway IP address, if one is present. If not, then comment out
the variable entirely.</para>

<para>The <envar>PREFIX</envar> variable needs to contain the
number of bits used in the subnet. Each octet in an IP address is 8
bits. If the subnet's netmask is 255.255.255.0, then it is using the
first three octets (24 bits) to specify the network number. If the
netmask is 255.255.255.240, it would be using the first 28 bits.
Prefixes longer than 24 bits are commonly used by DSL- and cable-based
Internet Service Providers (ISPs).  In this example (PREFIX=24), the netmask
is 255.255.255.0. Adjust according to the specific subnet.</para>

</sect2>

<sect2 id="resolv.conf">
<title>Creating the /etc/resolv.conf File</title>
<indexterm zone="resolv.conf"><primary sortas="e-/etc/resolv.conf">/etc/resolv.conf</primary></indexterm>

<para>If the system is going to be connected to the Internet, it will
need some means of Domain Name Service (DNS) name resolution to
resolve Internet domain names to IP addresses, and vice versa. This is
best achieved by placing the IP address of the DNS server, available
from the ISP or network administrator, into
<filename>/etc/resolv.conf</filename>. Create the file by running the
following:</para>

<screen><userinput>cat &gt; /etc/resolv.conf &lt;&lt; "EOF"
<literal># Begin /etc/resolv.conf

domain {<replaceable>[Your Domain Name]</replaceable>}
nameserver <replaceable>[IP address of your primary nameserver]</replaceable>
nameserver <replaceable>[IP address of your secondary nameserver]</replaceable>

# End /etc/resolv.conf</literal>
EOF</userinput></screen>

<para>Replace <replaceable>[IP address of the
nameserver]</replaceable> with the IP address of the DNS most
appropriate for the setup. There will often be more than one entry
(requirements demand secondary servers for fallback capability). If
you only need or want one DNS server, remove the second
<emphasis>nameserver</emphasis> line from the file. The IP address may
also be a router on the local network.</para>
</sect2>

</sect1>