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374 lines
15 KiB
XML
374 lines
15 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="systemd">
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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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<para>This section only applies if a network card is to be
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configured.</para>
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<sect2>
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<title>Network Interface Configuration Files</title>
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<para>Starting with version 209, systemd ships a network configuration
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daemon called <command>systemd-networkd</command> which can be used for
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basic network configuration. Additionally, since version 213, DNS name
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resolution can be handled by <command>systemd-resolved</command> in place
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of a static <filename>/etc/resolv.conf</filename> file. Both services are
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enabled by default.</para>
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<note>
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<para>
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If you will not use <command>systemd-networkd</command> for network
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configuration (for example, when the system is not connected to
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network, or you want to use another utility like NetworkManager
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for network configuration), disable a service to prevent an error
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message during boot:
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</para>
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<screen role='nodump'><userinput>systemctl disable systemd-networkd-wait-online</userinput></screen>
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</note>
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<para>Configuration files for <command>systemd-networkd</command> (and
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<command>systemd-resolved</command>) can be placed in
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<filename class="directory">/usr/lib/systemd/network</filename>
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or <filename class="directory">/etc/systemd/network</filename>. Files in
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<filename class="directory">/etc/systemd/network</filename> have a
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higher priority than the ones in
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<filename class="directory">/usr/lib/systemd/network</filename>.
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There are three types of configuration files:
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<filename class="extension">.link</filename>,
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<filename class="extension">.netdev</filename> and
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<filename class="extension">.network</filename> files. For detailed
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descriptions and example contents of these configuration files, consult
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the
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<ulink role='man' url='&man;systemd.link.5'>systemd.link(5)</ulink>,
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<ulink role='man' url='&man;systemd.netdev.5'>systemd.netdev(5)</ulink>, and
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<ulink role='man' url='&man;systemd.network.5'>systemd.network(5)</ulink>
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manual pages.</para>
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<sect3 id="systemd-network-devices">
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<title>Network Device Naming</title>
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<para>
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Udev normally assigns network card interface names based
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on physical system characteristics such as enp2s1. If you are
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not sure what your interface name is, you can always run
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<command>ip link</command> after you have booted your system.
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</para>
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<note>
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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 (<command>systemd-udevd</command>, installed in
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<xref linkend="ch-system-systemd"/>) will not run unless the LFS
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system is booted. So it's unreliable to determine the interface
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names being used in LFS system by running those commands on the host
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distro,
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<emphasis>even though you are in the chroot environment</emphasis>.</para>
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</note>
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<para>
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For most systems, there is only one network interface for
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each type of connection. For example, the classic interface
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name for a wired connection is eth0. A wireless connection
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will usually have the name wifi0 or wlan0.
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</para>
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<para>
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If you prefer to use the classic or customized network interface names,
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there are three alternative ways to do that:</para>
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<itemizedlist>
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<listitem>
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<para>
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Mask udev's <filename class='extension'>.link</filename> file
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for the default policy:
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<screen role="nodump"><userinput>ln -s /dev/null /etc/systemd/network/99-default.link</userinput></screen>
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</para>
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</listitem>
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<listitem>
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<para>
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Create a manual naming scheme, for example by naming the
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interfaces something like <literal>internet0</literal>,
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<literal>dmz0</literal>, or <literal>lan0</literal>.
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To do that, create <filename class='extension'>.link</filename>
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files in /etc/systemd/network/ that select an explicit name or a
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better naming scheme for your network interfaces. For example:
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</para>
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<screen role="nodump"><userinput>cat > /etc/systemd/network/10-ether0.link << "EOF"
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<literal>[Match]
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# Change the MAC address as appropriate for your network device
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MACAddress=12:34:45:78:90:AB
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[Link]
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Name=ether0</literal>
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EOF</userinput></screen>
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<para>
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See <ulink role='man' url='&man;systemd.link.5'>systemd.link(5)</ulink> for more information.
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</para>
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</listitem>
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<listitem>
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<para>
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In /boot/grub/grub.cfg, pass the option
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<option>net.ifnames=0</option> on the kernel command line.
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</para>
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</listitem>
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</itemizedlist>
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</sect3>
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<sect3 id="systemd-networkd-static">
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<title>Static IP Configuration</title>
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<para>The command below creates a basic configuration file for a
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Static IP setup (using both systemd-networkd and
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systemd-resolved):</para>
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<!-- jhalfs relies on the values for Name, Address, etc. If you want to change
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them, please inform the jhalfs maintainer(s). -->
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<screen><userinput>cat > /etc/systemd/network/10-eth-static.network << "EOF"
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<literal>[Match]
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Name=<replaceable><network-device-name></replaceable>
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[Network]
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Address=192.168.0.2/24
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Gateway=192.168.0.1
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DNS=192.168.0.1
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Domains=<replaceable><Your Domain Name></replaceable></literal>
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EOF</userinput></screen>
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<para>Multiple DNS entries can be added if you have more than one DNS
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server. Do not include DNS or Domains entries if you intend to use a
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static <filename>/etc/resolv.conf</filename> file.</para>
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</sect3>
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<sect3 id="systemd-networkd-dhcp">
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<title>DHCP Configuration</title>
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<para>The command below creates a basic configuration file for an IPv4
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DHCP setup:</para>
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<screen role="nodump"><userinput>cat > /etc/systemd/network/10-eth-dhcp.network << "EOF"
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<literal>[Match]
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Name=<network-device-name>
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[Network]
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DHCP=ipv4
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[DHCPv4]
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UseDomains=true</literal>
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EOF</userinput></screen>
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</sect3>
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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>If the system is going to be connected to the Internet, it will
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need some means of Domain Name Service (DNS) name resolution to
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resolve Internet domain names to IP addresses, and vice versa. This is
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best achieved by placing the IP address of the DNS server, available
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from the ISP or network administrator, into
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<filename>/etc/resolv.conf</filename>.</para>
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<sect3 id="resolv-conf-systemd-resolved">
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<title>systemd-resolved Configuration</title>
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<note><para>If using methods incompatible with systemd-resolved to
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configure your network interfaces (ex: ppp, etc.), or if using any
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type of local resolver (ex: bind, dnsmasq, unbound, etc.),
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or any other software that generates an <filename>/etc/resolv.conf</filename>
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(ex: a <command>resolvconf</command> program other than the one
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provided by systemd), the <command>systemd-resolved</command> service
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should not be used.</para>
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<para>To disable systemd-resolved, issue the following command:</para>
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<screen role="nodump"><userinput>systemctl disable systemd-resolved</userinput></screen></note>
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<para>When using <command>systemd-resolved</command> for DNS
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configuration, it creates the file
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<filename>/run/systemd/resolve/stub-resolv.conf</filename>.
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And, if <filename>/etc/resolv.conf</filename> does not exist, it
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will be created by <command>systemd-resolved</command> as a symlink to
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<filename>/run/systemd/resolve/stub-resolv.conf</filename>. So it's
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unnecessary to create a <filename>/etc/resolv.conf</filename>
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manually.</para>
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<!--Create a
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symlink in <filename>/etc</filename> to use the generated file:</para>
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<screen><userinput>ln -sfv /run/systemd/resolve/resolv.conf /etc/resolv.conf</userinput></screen>
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At least in systemd-250, this file gets created on first bootup.
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-->
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</sect3>
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<sect3 id="resolv-conf-static">
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<title>Static resolv.conf Configuration</title>
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<para>If a static <filename>/etc/resolv.conf</filename> is desired,
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create it by running the following command:</para>
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<screen role="nodump"><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
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for resolv.conf for more details.</para>
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<para>Replace
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<replaceable><IP address of the nameserver></replaceable>
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with the IP address of the DNS server most appropriate for your setup.
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There will often be more than one entry (requirements demand secondary
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servers for fallback capability). If you only need or want one DNS server,
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remove the second <emphasis>nameserver</emphasis> line from the file.
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The IP address may also be a router on the local network. Another option
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is to use the Google Public DNS service using the IP addresses below as
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nameservers.</para>
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<note><para>The Google Public IPv4 DNS addresses are
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<parameter>8.8.8.8</parameter> and <parameter>8.8.4.4</parameter>
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for IPv4, and <parameter>2001:4860:4860::8888</parameter> and
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<parameter>2001:4860:4860::8844</parameter> for IPv6.</para></note>
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</sect3>
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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 is put 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 using the following
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command:</para>
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<screen><userinput>cat > /etc/hosts << "EOF"
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<literal># Begin /etc/hosts
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<replaceable><192.168.0.2></replaceable> <replaceable><FQDN></replaceable> <replaceable>[alias1] [alias2] ...</replaceable>
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::1 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><192.168.0.2></replaceable> and
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<replaceable><FQDN></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, and the
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<replaceable><192.168.0.2></replaceable> line can be omitted if you
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are using a connection configured with DHCP or IPv6 Autoconfiguration,
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or using <literal>localhost.localdomain</literal> as the FQDN.</para>
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<para>The <filename>/etc/hostname</filename> does not contain entries
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for <literal>localhost</literal>,
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<literal>localhost.localdomain</literal>, or the hostname (without a
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domain) because they are handled by the
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<systemitem class='library'>myhostname</systemitem> NSS module, read
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the man page <ulink role='man'
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url='&man;nss-myhostname.8'>nss-myhostname(8)</ulink> for
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details.</para>
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<para>The ::1 entry is the IPv6 counterpart of 127.0.0.1 and represents
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the IPv6 loopback interface.</para>
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</sect2>
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</sect1>
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