lfs-book/chapter07/network.xml

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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>

<!-- Edit Me -->
<para>Which interfaces are brought up and down by the network script
depends on the files and directories in the <filename
class="directory">/etc/sysconfig/network-devices</filename> hierarchy.
This directory should contain a sub-directory for each interface to be configured,
such as <filename>ifconfig.xyz</filename>, where <quote>xyz</quote> is a
network interface name. Inside this directory would be files defining
the attributes to this interface, such as its IP address(es), subnet
masks, and so forth.</para>

<para>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 be brought up.</para>

<para>The <envar>SERVICE</envar> variable defines the method used for obtaining
the IP address. The LFS-Bootscripts package has 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 the <envar>PREFIX</envar> variable according to
your 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>

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