lfs/chapter07/networkd.xml
2016-10-27 23:22:45 +00:00

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<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY % general-entities SYSTEM "../general.ent">
%general-entities;
]>
<sect1 id="ch-scripts-network" revision="systemd">
<?dbhtml filename="network.html"?>
<title>General Network Configuration</title>
<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>
<sect2>
<title>Network Interface Configuration Files</title>
<para>Starting with version 209, systemd ships a network configuration
daemon called <command>systemd-networkd</command> which can be used for
basic network configuration. Additionally, since version 213, DNS name
resolution can be handled by <command>systemd-resolved</command> in place
of a static <filename>/etc/resolv.conf</filename> file. Both services are
enabled by default.</para>
<para>Configuration files for <command>systemd-networkd</command> (and
<command>systemd-resolved</command>) can be placed in
<filename class="directory">/usr/lib/systemd/network</filename>
or <filename class="directory">/etc/systemd/network</filename>. Files in
<filename class="directory">/etc/systemd/network</filename> have a
higher priority than the ones in
<filename class="directory">/usr/lib/systemd/network</filename>.
There are three types of configuration files:
<filename class="extension">.link</filename>,
<filename class="extension">.netdev</filename> and
<filename class="extension">.network</filename> files. For detailed
descriptions and example contents of these configuration files, consult
the <filename>systemd-link(5)</filename>,
<filename>systemd-netdev(5)</filename> and
<filename>systemd-network(5)</filename> manual pages.</para>
<note><para>Udev may assign network card interface names based
on system physical characteristics such as enp2s1. If you are
not sure what your interface name is, you can always run
<command>ip link</command> after you have booted your system.
</para></note>
<sect3 id="systemd-networkd-static">
<title>Static IP Configuration</title>
<para>The command below creates a basic configuration file for a
Static IP setup (using both systemd-networkd and
systemd-resolved):</para>
<screen role="nodump"><userinput>cat &gt; /etc/systemd/network/10-eth0-static.network &lt;&lt; "EOF"
<literal>[Match]
Name=eth0
[Network]
Address=192.168.0.2/24
Gateway=192.168.0.1
DNS=192.168.0.1
Domains=<replaceable>&lt;Your Domain Name&gt;</replaceable></literal>
EOF</userinput></screen>
<para>Multiple DNS entries can be added if you have more than one DNS
server. Do not include DNS or Domains entries if you intend to use a
static <filename>/etc/resolv.conf</filename> file.</para>
</sect3>
<sect3 id="systemd-networkd-dhcp">
<title>DHCP Configuration</title>
<para>The command below creates a basic configuration file for an IPv4
DHCP setup:</para>
<screen role="nodump"><userinput>cat &gt; /etc/systemd/network/10-eth0-dhcp.network &lt;&lt; "EOF"
<literal>[Match]
Name=eth0
[Network]
DHCP=ipv4
[DHCP]
UseDomains=true</literal>
EOF</userinput></screen>
</sect3>
</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>.</para>
<sect3 id="resolv-conf-systemd-resoloved">
<title>systemd-resolved Configuration</title>
<note><para>If using another means to configure your network
interfaces (ex: ppp, network-manager, etc.), or if using any type of
local resolver (ex: bind, dnsmasq, etc.), or any other software that
generates an <filename>/etc/resolv.conf</filename> (ex: resolvconf), the
<command>systemd-resolved</command> service should not be
used.</para></note>
<para>When using <command>systemd-resolved</command> for DNS
configuration, it creates the file
<filename>/run/systemd/resolve/resolv.conf</filename>. Create a
symlink in <filename>/etc</filename> to use the generatd file:</para>
<screen><userinput remap="install">ln -sfv /run/systemd/resolve/resolv.conf /etc/resolv.conf</userinput></screen>
</sect3>
<sect3 id="resolv-conf-static">
<title>Static resolv.conf Configuration</title>
<para>If a static <filename>/etc/resolv.conf</filename> is desired,
create it by running the following command:</para>
<screen role="nodump"><userinput>cat &gt; /etc/resolv.conf &lt;&lt; "EOF"
<literal># Begin /etc/resolv.conf
domain <replaceable>&lt;Your Domain Name&gt;</replaceable>
nameserver <replaceable>&lt;IP address of your primary nameserver&gt;</replaceable>
nameserver <replaceable>&lt;IP address of your secondary nameserver&gt;</replaceable>
# End /etc/resolv.conf</literal>
EOF</userinput></screen>
<para>The <varname>domain</varname> statement can be omitted
or replaced with a <varname>search</varname> statement. See the man page
for resolv.conf for more details.</para>
<para>Replace
<replaceable>&lt;IP address of the nameserver&gt;</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>
<note><para>The Google Public IPv4 DNS addresses are
<parameter>8.8.8.8</parameter> and <parameter>8.8.4.4</parameter>
for IPv4, and <parameter>2001:4860:4860::8888</parameter> and
<parameter>2001:4860:4860::8844</parameter> for IPv6.</para></note>
</sect3>
</sect2>
<sect2 id="ch-scripts-hostname">
<title>Configuring the system hostname</title>
<indexterm zone="ch-scripts-hostname">
<primary sortas="d-hostname">hostname</primary>
<secondary>configuring</secondary>
</indexterm>
<para>During the boot process, the file <filename>/etc/hostname</filename>
is used for establishing the system's hostname.</para>
<para>Create the <filename>/etc/hostname</filename> file and enter a
hostname by running:</para>
<screen><userinput>echo "<replaceable>&lt;lfs&gt;</replaceable>" &gt; /etc/hostname</userinput></screen>
<para><replaceable>&lt;lfs&gt;</replaceable> needs to be replaced with the
name given to the computer. Do not enter the Fully Qualified Domain Name
(FQDN) here. That information is put in the
<filename>/etc/hosts</filename> file.</para>
</sect2>
<sect2 id="ch-scripts-hosts">
<title>Customizing the /etc/hosts File</title>
<indexterm zone="ch-scripts-hosts">
<primary sortas="e-/etc/hosts">/etc/hosts</primary>
</indexterm>
<indexterm zone="ch-scripts-hosts">
<primary sortas="d-localnet">localnet</primary>
<secondary>/etc/hosts</secondary>
</indexterm>
<indexterm zone="ch-scripts-hosts">
<primary sortas="d-network">network</primary>
<secondary>/etc/hosts</secondary>
</indexterm>
<para>Decide on a fully-qualified domain name (FQDN), and possible aliases
for use in the <filename>/etc/hosts</filename> file. If using static
addresses, you'll also need to decide on an IP address. The syntax
for a hosts file entry is:</para>
<screen><literal>IP_address myhost.example.org aliases</literal></screen>
<para>Unless the computer is to be visible to the Internet (i.e., there is
a registered domain and a valid block of assigned IP addresses&mdash;most
users do not have this), make sure that the IP address is in the private
network IP address range. Valid ranges are:</para>
<screen><literal>Private Network Address Range Normal Prefix
10.0.0.1 - 10.255.255.254 8
172.x.0.1 - 172.x.255.254 16
192.168.y.1 - 192.168.y.254 24</literal></screen>
<para>x can be any number in the range 16-31. y can be any number in the
range 0-255.</para>
<para>A valid private IP address could be 192.168.1.1. A valid FQDN for
this IP could be lfs.example.org.</para>
<para>Even if not using a network card, a valid FQDN is still required.
This is necessary for certain programs to operate correctly.</para>
<para>If using DHCP, DHCPv6, IPv6 Autoconfiguration, or if a network card
is not going to be configured, create the <filename>/etc/hosts</filename>
file by running the following command:</para>
<screen><userinput>cat &gt; /etc/hosts &lt;&lt; "EOF"
<literal># Begin /etc/hosts
127.0.0.1 <replaceable>&lt;HOSTNAME.example.org&gt;</replaceable> <replaceable>&lt;HOSTNAME&gt;</replaceable> localhost <replaceable>[alias1] [alias2] ...</replaceable>
::1 <replaceable>&lt;HOSTNAME.example.org&gt;</replaceable> <replaceable>&lt;HOSTNAME&gt;</replaceable> localhost <replaceable>[alias1] [alias2] ...</replaceable>
# End /etc/hosts</literal>
EOF</userinput></screen>
<para>The ::1 entry is the IPv6 counterpart of 127.0.0.1 and represents
the IPv6 loopback interface.</para>
<para>If using a static address, create the <filename>/etc/hosts</filename>
file by running this command instead:</para>
<screen role="nodump"><userinput>cat &gt; /etc/hosts &lt;&lt; "EOF"
<literal># Begin /etc/hosts
127.0.0.1 localhost
::1 localhost
<replaceable>&lt;192.168.0.2&gt;</replaceable> <replaceable>&lt;HOSTNAME.example.org&gt;</replaceable> <replaceable>&lt;HOSTNAME&gt;</replaceable> <replaceable>[alias1] [alias2] ...</replaceable>
# End /etc/hosts</literal>
EOF</userinput></screen>
<para>The <replaceable>&lt;192.168.0.2&gt;</replaceable>,
<replaceable>&lt;HOSTNAME.example.org&gt;</replaceable>, and
<replaceable>&lt;HOSTNAME&gt;</replaceable> values need to be
changed for specific uses or requirements (if assigned an IP address by a
network/system administrator and the machine will be connected to an
existing network). The optional alias name(s) can be omitted.</para>
</sect2>
</sect1>