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94e3e7bdd1
Add discussion of ethernet device names (systemd). Add discussion of audo file deletion (systemd). Add discussion of separate /tmp (systemd). git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@11340 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689
335 lines
12 KiB
XML
335 lines
12 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1"?>
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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-scripts-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-scripts-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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<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 <filename>systemd-link(5)</filename>,
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<filename>systemd-netdev(5)</filename> and
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<filename>systemd-network(5)</filename> 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 system physical 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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<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 .link file 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 "internet0", "dmz0", or "lan0".
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For that, create .link
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files in /etc/systemd/network/, that choose an explicit name or a
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better naming scheme for one, some, or all of your interfaces.
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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 the man page systemd.link(5) 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 net.ifnames=0 on the
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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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<screen><userinput>cat > /etc/systemd/network/10-eth-static.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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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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[DHCP]
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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 another means to configure your network
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interfaces (ex: ppp, network-manager, etc.), or if using any type of
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local resolver (ex: bind, dnsmasq, etc.), or any other software that
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generates an <filename>/etc/resolv.conf</filename> (ex: resolvconf), the
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<command>systemd-resolved</command> service should not be
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used.</para></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/resolv.conf</filename>. 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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</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 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><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-scripts-hostname">
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<title>Configuring the system hostname</title>
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<indexterm zone="ch-scripts-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-scripts-hosts">
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<title>Customizing the /etc/hosts File</title>
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<indexterm zone="ch-scripts-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-scripts-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-scripts-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
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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. A valid FQDN for
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this IP could be lfs.example.org.</para>
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<para>Even if not using a network card, a valid FQDN is still required.
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This is necessary for certain programs to operate correctly.</para>
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<para>If using DHCP, DHCPv6, IPv6 Autoconfiguration, or if a network card
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is not going to be configured, create the <filename>/etc/hosts</filename>
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file by running the following command:</para>
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<screen role="nodump"><userinput>cat > /etc/hosts << "EOF"
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<literal># Begin /etc/hosts
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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</literal>
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EOF</userinput></screen>
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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. 127.0.1.1 is a loopback entry reserved
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specifically for the FQDN.</para>
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<para>If using a static address, create the <filename>/etc/hosts</filename>
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file by running this command instead:</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
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127.0.1.1 <replaceable><FQDN></replaceable> <replaceable><HOSTNAME></replaceable>
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<replaceable><192.168.0.2></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><192.168.0.2></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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</sect2>
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</sect1>
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