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<section begin=Body/>
== Introduction How to configure the network interfaces ==
Once the Embedded Device is finally configured for stand-alone bootstrap, the network interface has to should be automatically configured for reaching the device remotely via netowrk network connections like ssh, telnet, ftp, htpphttp, etc.
This Application Note briefly describes how it is possible to simply configure the network interfaces on [https://en.wikipedia.org/wiki/UNIX_System_V SystemV] (aka ''SysV'') or [https://www.freedesktop.org/wiki/Software/systemd/ systemd]
=== Resources ===
For further details on network configuration, please refer - for example - to:
* [https://www.freedesktop.org/software/systemd/man/systemd.network.html systemd network configuration]
=== Examples===
The following configuration assumptions are used in the paragraphs shown below:
* IP address range of the LAN network '''192.168.1.0 - 192.168.1.255'''
* IP address of the gateway '''192.168.1.254'''
* IP address of the PC device '''192.168.1.100'''
=== SysV ===
The configuration files for SysV can be found in pre-defined directorys as written [https://en.wikibooks.org/wiki/Linux_Networking/Where_should_I_put_the_configuration_commands%3F here]
Basically, for network configuration, it should be enough to properly configure the <code>/etc/network/interfaces</code> file.
# /etc/network/interfaces -- configuration file for ifup(8), ifdown(8)
Here below an example of configuration file:
==== Static IP address ====
The network interface is configured with a static IP address by creating the configuration entry in the '''/etc/network/interfaces''' file as the following:
<pre>
auto eth0
iface eth0 inet static
address 192.168.1.100
</pre>
==== Dynamic IP addres (DHCP) ====
The network interface is configured - using a proper DHCP server on the network - by creating the configuration entry in the '''/etc/network/interfaces''' file as the following:
When the Linux kernel detects the physical interface eth0, the iface causes ''ifup'' to use DHCP to configure the interface.
==== DNS ====
If the <code>resolvconf</code> package is not installed, the DNS configuration can be done manually by editing the '''/etc/resolv.conf''' as the following:
root@axel-lite:~# echo "nameserver 192.168.1.1" > /etc/resolv.conf
==== loopback network interface ====
The following configuration entry in the '''/etc/network/interfaces''' file brings up the loopback network interface lo upon booting the system (via auto stanza).
<pre>
# The loopback interface
auto lo
iface lo inet loopback
This one always exists in the ''/etc/network/interfaces'' file.
=== systemd ===
The network configuration for systemd are basically found in the <code>/etc/systemd/network/</code> directory.
The most simply way for configuring the network interface is to create/edit the file '''/etc/systemd/network/20-eth0.network''' as per te the following paragraphs.
For more example and usage hints on systemd, please refer to our [[XELK-AN-008:_How_to_use_systemd_on_an_Embedded_system#Configuring_the_network_interfaces | wiki]] page. ==== Static IP address ====
<pre>
</pre>
Once modified, the <code>networkd</code> service should be resarted: systemctl restart systemd-networkd ==== Dynamic IP addres (DHCP) ====
The network interface is configured - using a proper DHCP server on the network - by using the '''DHCP''' key in the configuration file as the following:
When systemd network starts, it tries to use a DHCP server present in the network to configure the interface.
==== DNS ====
The DNS key (in the configuration file) is used only if the '''systemd-resolved service ''' is enabled and the '''/etc/resolv.conf''' has a symbolic link to '''/run/systemd/resolve/stub-resolv.conf'''
ln -sf /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf
Once modified, the <code>resolved</code> service should be resarted:
systemctl restart systemd-resolved
==== loopback network interface ====
systemd contains native implementations of various tasks that need to be executed as part of the boot process.
For example, it sets the hostname or configures the loopback network device.
==== Apply configuration changes ====
After editing the above files, changes are applied after reboot or by restarting <code>systemd-networkd.service</code>:<syntaxhighlight lang="bash">
root@imx6qdlxelk:~# systemctl restart systemd-networkd.service
</syntaxhighlight>
