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256 lines
11 KiB
XML
256 lines
11 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY % general-entities SYSTEM "../general.ent">
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%general-entities;
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]>
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<sect1 id="ch-config-network" revision="sysv">
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<?dbhtml filename="network.html"?>
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<title>General Network Configuration</title>
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<indexterm zone="ch-config-network">
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<primary sortas="d-network">network</primary>
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<secondary>configuring</secondary></indexterm>
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<sect2>
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<title>Creating Network Interface Configuration Files</title>
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<para>The files in <filename class="directory">/etc/sysconfig/</filename>
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usually determine which interfaces are brought up and down by the network
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script. This directory should
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contain a file for each interface to be configured, such as
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<filename>ifconfig.xyz</filename>, where <quote>xyz</quote> describes
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the network card. The interface name (e.g. eth0) is usually appropriate.
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Each file contains the attributes of one interface, such as its IP
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address(es), subnet masks, and so forth. The stem of
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the filename must be <emphasis>ifconfig</emphasis>.</para>
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<note>
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<para>If the procedure in the previous section was not used, udev
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will assign network card interface names based on system physical
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characteristics such as enp2s1. If you are not sure what your interface
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name is, you can always run <command>ip link</command> or <command>ls
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/sys/class/net</command> after you have booted your system.
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</para>
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<para>The interface names depend on the implementation and
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configuration of the udev daemon running on the system. The udev
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daemon for LFS (installed in <xref linkend="ch-system-udev"/>) will
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not run until the LFS system is booted. So the interface names
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in the LFS system cannot always be determined by running
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those commands on the host distro,
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<emphasis>even in the chroot environment</emphasis>.</para>
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</note>
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<para>The following command creates a sample file for the
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<emphasis>eth0</emphasis> device with a static IP address:</para>
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<!-- jhalfs relies on the values for IFACE, IP, etc. If you want to change
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them, please inform the jhalfs maintainer(s). -->
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<screen><userinput>cd /etc/sysconfig/
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cat > ifconfig.<replaceable>eth0</replaceable> << "EOF"
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<literal>ONBOOT=<replaceable>yes</replaceable>
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IFACE=<replaceable>eth0</replaceable>
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SERVICE=<replaceable>ipv4-static</replaceable>
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IP=<replaceable>192.168.1.2</replaceable>
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GATEWAY=<replaceable>192.168.1.1</replaceable>
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PREFIX=<replaceable>24</replaceable>
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BROADCAST=<replaceable>192.168.1.255</replaceable></literal>
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EOF</userinput></screen>
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<para>The values in italics must be changed in each file, to set
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the interfaces up correctly.</para>
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<para>If the <envar>ONBOOT</envar> variable is set to <quote>yes</quote> the
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System V network script will bring up the Network Interface Card (NIC) during
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the system boot process. If set to anything besides <quote>yes</quote>, the NIC
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will be ignored by the network script and will not be started automatically.
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Interfaces can be manually started or stopped with the
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<command>ifup</command> and <command>ifdown</command> commands.</para>
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<para>The <envar>IFACE</envar> variable defines the interface name,
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for example, eth0. It is required for all network device configuration
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files. The filename extension must match this value.</para>
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<para>The <envar>SERVICE</envar> variable defines the method used for
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obtaining the IP address. The LFS-Bootscripts package has a modular IP
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assignment format, and creating additional files in the <filename
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class="directory">/lib/services/</filename> directory allows other IP
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assignment methods. This is commonly used for Dynamic Host Configuration
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Protocol (DHCP), which is addressed in the BLFS book.</para>
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<para>The <envar>GATEWAY</envar> variable should contain the default
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gateway IP address, if one is present. If not, then comment out the
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variable entirely.</para>
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<para>The <envar>PREFIX</envar> variable specifies the number of
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bits used in the subnet. Each segment of an IP address is 8 bits. If the
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subnet's netmask is 255.255.255.0, then it is using the first three segments
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(24 bits) to specify the network number. If the netmask is 255.255.255.240,
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the subnet is using the first 28 bits. Prefixes longer than 24 bits are
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commonly used by DSL and cable-based Internet Service Providers (ISPs).
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In this example (PREFIX=24), the netmask is 255.255.255.0. Adjust the
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<envar>PREFIX</envar> variable according to your specific subnet.
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If omitted, the PREFIX defaults to 24.</para>
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<para>For more information see the <command>ifup</command> man page.</para>
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</sect2>
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<sect2 id="resolv.conf">
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<title>Creating the /etc/resolv.conf File</title>
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<indexterm zone="resolv.conf">
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<primary sortas="e-/etc/resolv.conf">/etc/resolv.conf</primary>
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</indexterm>
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<para>The system will need some means of obtaining Domain Name Service
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(DNS) name resolution to resolve Internet domain names to IP addresses, and
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vice versa. This is best achieved by placing the IP address of the DNS
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server, available from the ISP or network administrator, into
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<filename>/etc/resolv.conf</filename>. Create the file by running the
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following:</para>
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<screen><userinput>cat > /etc/resolv.conf << "EOF"
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<literal># Begin /etc/resolv.conf
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domain <replaceable><Your Domain Name></replaceable>
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nameserver <replaceable><IP address of your primary nameserver></replaceable>
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nameserver <replaceable><IP address of your secondary nameserver></replaceable>
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# End /etc/resolv.conf</literal>
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EOF</userinput></screen>
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<para>The <varname>domain</varname> statement can be omitted
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or replaced with a <varname>search</varname> statement. See the man page for
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resolv.conf for more details.</para>
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<para>Replace <replaceable><IP address of the nameserver></replaceable>
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with the IP address of the DNS most appropriate for the setup. There will
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often be more than one entry (requirements demand secondary servers for
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fallback capability). If you only need or want one DNS server, remove the
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second <emphasis>nameserver</emphasis> line from the file. The IP address
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may also be a router on the local network.</para>
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<note>
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<para>The Google Public IPv4 DNS addresses are 8.8.8.8 and 8.8.4.4.</para>
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</note>
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</sect2>
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<sect2 id="ch-config-hostname">
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<title>Configuring the System Hostname</title>
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<indexterm zone="ch-config-hostname">
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<primary sortas="d-hostname">hostname</primary>
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<secondary>configuring</secondary>
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</indexterm>
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<para>During the boot process, the file <filename>/etc/hostname</filename>
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is used for establishing the system's hostname.</para>
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<para>Create the <filename>/etc/hostname</filename> file and enter a
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hostname by running:</para>
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<screen><userinput>echo "<replaceable><lfs></replaceable>" > /etc/hostname</userinput></screen>
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<para><replaceable><lfs></replaceable> needs to be replaced with the
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name given to the computer. Do not enter the Fully Qualified Domain Name
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(FQDN) here. That information goes in the
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<filename>/etc/hosts</filename> file.</para>
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</sect2>
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<sect2 id="ch-config-hosts">
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<title>Customizing the /etc/hosts File</title>
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<indexterm zone="ch-config-hosts">
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<primary sortas="e-/etc/hosts">/etc/hosts</primary>
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</indexterm>
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<indexterm zone="ch-config-hosts">
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<primary sortas="d-localnet">localnet</primary>
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<secondary>/etc/hosts</secondary>
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</indexterm>
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<indexterm zone="ch-config-hosts">
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<primary sortas="d-network">network</primary>
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<secondary>/etc/hosts</secondary>
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</indexterm>
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<para>Decide on a fully-qualified domain name (FQDN), and possible aliases
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for use in the <filename>/etc/hosts</filename> file. If using static IP
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addresses, you'll also need to decide on an IP address. The syntax
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for a hosts file entry is:</para>
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<screen><literal>IP_address myhost.example.org aliases</literal></screen>
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<para>Unless the computer is to be visible to the Internet (i.e., there is
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a registered domain and a valid block of assigned IP addresses—most
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users do not have this), make sure that the IP address is in the private
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network IP address range. Valid ranges are:</para>
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<screen><literal>Private Network Address Range Normal Prefix
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10.0.0.1 - 10.255.255.254 8
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172.x.0.1 - 172.x.255.254 16
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192.168.y.1 - 192.168.y.254 24</literal></screen>
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<para>x can be any number in the range 16-31. y can be any number in the
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range 0-255.</para>
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<para>A valid private IP address could be 192.168.1.1.</para>
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<para>If the computer is to be visible to the Internet, a valid FQDN
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can be the domain name itself, or a string resulted by concatenating a
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prefix (often the hostname) and the domain name with a <quote>.</quote>
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character. And, you need to contact the domain provider to resolve the
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FQDN to your public IP address.</para>
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<para>Even if the computer is not visible to the Internet, a FQDN is
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still needed for certain programs, such as MTAs, to operate properly.
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A special FQDN, <literal>localhost.localdomain</literal>, can be used
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for this purpose.</para>
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<para>Create the <filename>/etc/hosts</filename> file by running:</para>
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<screen><userinput>cat > /etc/hosts << "EOF"
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<literal># Begin /etc/hosts
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127.0.0.1 localhost.localdomain localhost
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127.0.1.1 <replaceable><FQDN></replaceable> <replaceable><HOSTNAME></replaceable>
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<replaceable><192.168.1.1></replaceable> <replaceable><FQDN></replaceable> <replaceable><HOSTNAME></replaceable> <replaceable>[alias1] [alias2 ...]</replaceable>
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::1 localhost ip6-localhost ip6-loopback
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ff02::1 ip6-allnodes
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ff02::2 ip6-allrouters
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# End /etc/hosts</literal>
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EOF</userinput></screen>
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<para>The <replaceable><192.168.1.1></replaceable>,
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<replaceable><FQDN></replaceable>, and
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<replaceable><HOSTNAME></replaceable> values need to be
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changed for specific uses or requirements (if assigned an IP address by a
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network/system administrator and the machine will be connected to an
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existing network). The optional alias name(s) can be omitted.</para>
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<!-- This is not very useful
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<para>If a network card is not going to be configured, create the
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<filename>/etc/hosts</filename> file by running:</para>
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<screen role="nodump"><userinput>cat > /etc/hosts << "EOF"
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<literal># Begin /etc/hosts (no network card version)
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127.0.0.1 localhost
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127.0.1.1 <replaceable><FQDN></replaceable> <replaceable><HOSTNAME></replaceable>
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::1 localhost ip6-localhost ip6-loopback
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ff02::1 ip6-allnodes
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ff02::2 ip6-allrouters
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# End /etc/hosts (no network card version)</literal>
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EOF</userinput></screen> -->
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</sect2>
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</sect1>
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