network.xml 12 KB

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  1. <?xml version="1.0" encoding="ISO-8859-1"?>
  2. <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  3. "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  4. <!ENTITY % general-entities SYSTEM "../general.ent">
  5. %general-entities;
  6. ]>
  7. <sect1 id="ch-scripts-network" revision="sysv">
  8. <?dbhtml filename="network.html"?>
  9. <title>General Network Configuration</title>
  10. <indexterm zone="ch-scripts-network">
  11. <primary sortas="d-network">network</primary>
  12. <secondary>configuring</secondary></indexterm>
  13. <para>This section only applies if a network card is to be
  14. configured.</para>
  15. <para>If a network card will not be used, there is likely no need to create
  16. any configuration files relating to network cards. If that is the case, you
  17. will need to remove the <filename class="symlink">network</filename> symlinks
  18. from all run-level directories (<filename
  19. class="directory">/etc/rc.d/rc*.d</filename>) after the bootscripts are
  20. installed in <xref linkend="ch-scripts-bootscripts"/>.</para>
  21. <sect2>
  22. <title>Creating Network Interface Configuration Files</title>
  23. <para>Which interfaces are brought up and down by the network script
  24. usually depends on the files in <filename
  25. class="directory">/etc/sysconfig/</filename>. This directory should
  26. contain a file for each interface to be configured, such as
  27. <filename>ifconfig.xyz</filename>, where <quote>xyz</quote> is required to
  28. be a Network Card Interface name (e.g. eth0). Inside this file are
  29. attributes to this interface, such as its IP address(es), subnet masks, and
  30. so forth. It is necessary that the stem of the filename be
  31. <emphasis>ifconfig</emphasis>.</para>
  32. <note><para>If the procedure in the previous section was not used, Udev
  33. will assign network card interface names based on system physical
  34. characteristics such as enp2s1. If you are not sure what your interface
  35. name is, you can always run <command>ip link</command> after you have
  36. booted your system. Again, it is important that ifconfig.xyz is named
  37. after correct network card interface name (e.g. ifconfig.enp2s1 or
  38. ifconfig.eth0) or your network interface will not be initialized during
  39. the boot process.</para></note>
  40. <para>The following command creates a sample file for the
  41. <emphasis>eth0</emphasis> device with a static IP address:</para>
  42. <screen><userinput>cd /etc/sysconfig/
  43. cat &gt; ifconfig.eth0 &lt;&lt; "EOF"
  44. <literal>ONBOOT=yes
  45. IFACE=eth0
  46. SERVICE=ipv4-static
  47. IP=192.168.1.2
  48. GATEWAY=192.168.1.1
  49. PREFIX=24
  50. BROADCAST=192.168.1.255</literal>
  51. EOF</userinput></screen>
  52. <para>The values of these variables must be changed in every file to match
  53. the proper setup.</para>
  54. <para>If the <envar>ONBOOT</envar> variable is set to <quote>yes</quote> the
  55. System V network script will bring up the Network Interface Card (NIC) during
  56. booting of the system. If set to anything but <quote>yes</quote> the NIC
  57. will be ignored by the network script and not be automatically brought up.
  58. The interface can be manually started or stopped with the
  59. <command>ifup</command> and <command>ifdown</command> commands.</para>
  60. <para>The <envar>IFACE</envar> variable defines the interface name,
  61. for example, eth0. It is required for all network device configuration
  62. files. </para>
  63. <para>The <envar>SERVICE</envar> variable defines the method used for
  64. obtaining the IP address. The LFS-Bootscripts package has a modular IP
  65. assignment format, and creating additional files in the <filename
  66. class="directory">/lib/services/</filename> directory allows other IP
  67. assignment methods. This is commonly used for Dynamic Host Configuration
  68. Protocol (DHCP), which is addressed in the BLFS book.</para>
  69. <para>The <envar>GATEWAY</envar> variable should contain the default
  70. gateway IP address, if one is present. If not, then comment out the
  71. variable entirely.</para>
  72. <para>The <envar>PREFIX</envar> variable contains the number of
  73. bits used in the subnet. Each octet in an IP address is 8 bits. If the
  74. subnet's netmask is 255.255.255.0, then it is using the first three octets
  75. (24 bits) to specify the network number. If the netmask is 255.255.255.240,
  76. it would be using the first 28 bits. Prefixes longer than 24 bits are
  77. commonly used by DSL and cable-based Internet Service Providers (ISPs).
  78. In this example (PREFIX=24), the netmask is 255.255.255.0. Adjust the
  79. <envar>PREFIX</envar> variable according to your specific subnet.
  80. If omitted, the PREFIX defaults to 24.</para>
  81. <para>For more information see the <command>ifup</command> man page.</para>
  82. </sect2>
  83. <!--
  84. <sect2 id="systemd-net-enable">
  85. <title>Configuring the Network Interface Card at boot (systemd)</title>
  86. <para>Enabling of the network interface card configuration
  87. in systemd is done per interface. To enable network interface card
  88. configuration at boot, run:</para>
  89. <screen><userinput>systemctl enable ifupdown@eth0</userinput></screen>
  90. <para>To disable a previously enabled network interface
  91. card configuration at boot, run:</para>
  92. <screen role="nodump"><userinput>systemctl disable ifupdown@eth0</userinput></screen>
  93. <para>To manually start the network interface card configuration,
  94. run:</para>
  95. <screen role="nodump"><userinput>systemctl start ifupdown@eth0</userinput></screen>
  96. <para>Replace eth0 with the correct network interface card
  97. name as described on the beginning of this page.</para>
  98. <note><para>These procedures require the configuration files as specified
  99. in the previous section.</para></note>
  100. <note><para>The network card can also be started or stopped
  101. with the traditional <command>ifup &lt;device&gt;</command> or
  102. <command>ifdown &lt;device&gt;</command> commands.</para></note>
  103. </sect2>
  104. <sect2 id="systemd2-net-enable">
  105. <title>Configuring the Network Interface Card for systemd-networkd</title>
  106. <para>An alternative way to configure a NIC when booting with with
  107. systemd is to create a configuration file recognized by the
  108. systemd-networkd daemon. To configure the device create a file similar
  109. to this:</para>
  110. <screen role="nodump"><userinput>cat &gt; /etc/systemd/network/10-static-eth0.network &lt;&lt; "EOF"
  111. [Match]
  112. Name=eth0
  113. [Network]
  114. Address=192.168.0.2/24
  115. Gateway=192.168.0.1
  116. EOF</userinput></screen>
  117. <para>You can use multiple .network files if desired. You can also specify
  118. DHCP=yes instead of the Address and Gateway settings. See the man page for
  119. systemd.network for more details,</para>
  120. <note><para>If this method is used, be sure to disable ifupdown@eth0 as
  121. described in the previous section (if it was enabled).</para></note>
  122. </sect2>
  123. -->
  124. <sect2 id="resolv.conf">
  125. <title>Creating the /etc/resolv.conf File</title>
  126. <indexterm zone="resolv.conf">
  127. <primary sortas="e-/etc/resolv.conf">/etc/resolv.conf</primary>
  128. </indexterm>
  129. <para>If the system is going to be connected to the Internet, it will
  130. need some means of Domain Name Service (DNS) name resolution to
  131. resolve Internet domain names to IP addresses, and vice versa. This is
  132. best achieved by placing the IP address of the DNS server, available
  133. from the ISP or network administrator, into
  134. <filename>/etc/resolv.conf</filename>. Create the file by running the
  135. following:</para>
  136. <screen><userinput>cat &gt; /etc/resolv.conf &lt;&lt; "EOF"
  137. <literal># Begin /etc/resolv.conf
  138. domain <replaceable>&lt;Your Domain Name&gt;</replaceable>
  139. nameserver <replaceable>&lt;IP address of your primary nameserver&gt;</replaceable>
  140. nameserver <replaceable>&lt;IP address of your secondary nameserver&gt;</replaceable>
  141. # End /etc/resolv.conf</literal>
  142. EOF</userinput></screen>
  143. <para>The <varname>domain</varname> statement can be omitted
  144. or replaced with a <varname>search</varname> statement. See the man page for
  145. resolv.conf for more details.</para>
  146. <para>Replace <replaceable>&lt;IP address of the nameserver&gt;</replaceable>
  147. with the IP address of the DNS most appropriate for the setup. There will
  148. often be more than one entry (requirements demand secondary servers for
  149. fallback capability). If you only need or want one DNS server, remove the
  150. second <emphasis>nameserver</emphasis> line from the file. The IP address
  151. may also be a router on the local network.</para>
  152. <note><para>The Google Public IPv4 DNS addresses are 8.8.8.8 and 8.8.4.4.</para></note>
  153. </sect2>
  154. <sect2 id="ch-scripts-hostname">
  155. <title>Configuring the system hostname</title>
  156. <indexterm zone="ch-scripts-hostname">
  157. <primary sortas="d-hostname">hostname</primary>
  158. <secondary>configuring</secondary>
  159. </indexterm>
  160. <para>During the boot process, the file <filename>/etc/hostname</filename>
  161. is used for establishing the system's hostname.</para>
  162. <para>Create the <filename>/etc/hostname</filename> file and enter a
  163. hostname by running:</para>
  164. <screen><userinput>echo "<replaceable>&lt;lfs&gt;</replaceable>" &gt; /etc/hostname</userinput></screen>
  165. <para><replaceable>&lt;lfs&gt;</replaceable> needs to be replaced with the
  166. name given to the computer. Do not enter the Fully Qualified Domain Name
  167. (FQDN) here. That information is put in the
  168. <filename>/etc/hosts</filename> file.</para>
  169. </sect2>
  170. <sect2 id="ch-scripts-hosts">
  171. <title>Customizing the /etc/hosts File</title>
  172. <indexterm zone="ch-scripts-hosts">
  173. <primary sortas="e-/etc/hosts">/etc/hosts</primary>
  174. </indexterm>
  175. <indexterm zone="ch-scripts-hosts">
  176. <primary sortas="d-localnet">localnet</primary>
  177. <secondary>/etc/hosts</secondary>
  178. </indexterm>
  179. <indexterm zone="ch-scripts-hosts">
  180. <primary sortas="d-network">network</primary>
  181. <secondary>/etc/hosts</secondary>
  182. </indexterm>
  183. <para>Decide on the IP address, fully-qualified domain name (FQDN), and
  184. possible aliases for use in the <filename>/etc/hosts</filename> file. The
  185. syntax is:</para>
  186. <screen><literal>IP_address myhost.example.org aliases</literal></screen>
  187. <para>Unless the computer is to be visible to the Internet (i.e., there is
  188. a registered domain and a valid block of assigned IP addresses&mdash;most
  189. users do not have this), make sure that the IP address is in the private
  190. network IP address range. Valid ranges are:</para>
  191. <screen><literal>Private Network Address Range Normal Prefix
  192. 10.0.0.1 - 10.255.255.254 8
  193. 172.x.0.1 - 172.x.255.254 16
  194. 192.168.y.1 - 192.168.y.254 24</literal></screen>
  195. <para>x can be any number in the range 16-31. y can be any number in the
  196. range 0-255.</para>
  197. <para>A valid private IP address could be 192.168.1.1. A valid FQDN for
  198. this IP could be lfs.example.org.</para>
  199. <para>Even if not using a network card, a valid FQDN is still required.
  200. This is necessary for certain programs to operate correctly.</para>
  201. <para>Create the <filename>/etc/hosts</filename> file by running:</para>
  202. <screen><userinput>cat &gt; /etc/hosts &lt;&lt; "EOF"
  203. <literal># Begin /etc/hosts (network card version)
  204. 127.0.0.1 localhost
  205. 127.0.1.1 <replaceable>&lt;FQDN&gt;</replaceable> <replaceable>&lt;HOSTNAME&gt;</replaceable>
  206. <replaceable>&lt;192.168.1.1&gt;</replaceable> <replaceable>&lt;FQDN&gt;</replaceable> <replaceable>&lt;HOSTNAME&gt;</replaceable> <replaceable>[alias1] [alias2 ...]</replaceable>
  207. ::1 localhost ip6-localhost ip6-loopback
  208. ff02::1 ip6-allnodes
  209. ff02::2 ip6-allrouters
  210. # End /etc/hosts (network card version)</literal>
  211. EOF</userinput></screen>
  212. <para>The <replaceable>&lt;192.168.1.1&gt;</replaceable>,
  213. <replaceable>&lt;FQDN&gt;</replaceable>, and
  214. <replaceable>&lt;HOSTNAME&gt;</replaceable> values need to be
  215. changed for specific uses or requirements (if assigned an IP address by a
  216. network/system administrator and the machine will be connected to an
  217. existing network). The optional alias name(s) can be omitted.</para>
  218. <para>If a network card is not going to be configured, create the
  219. <filename>/etc/hosts</filename> file by running:</para>
  220. <screen role="nodump"><userinput>cat &gt; /etc/hosts &lt;&lt; "EOF"
  221. <literal># Begin /etc/hosts (no network card version)
  222. 127.0.0.1 localhost
  223. 127.0.1.1 <replaceable>&lt;FQDN&gt;</replaceable> <replaceable>&lt;HOSTNAME&gt;</replaceable>
  224. ::1 localhost ip6-localhost ip6-loopback
  225. ff02::1 ip6-allnodes
  226. ff02::2 ip6-allrouters
  227. # End /etc/hosts (no network card version)</literal>
  228. EOF</userinput></screen>
  229. </sect2>
  230. </sect1>