View source for How to configure the network interfaces

== How to configure the network interfaces ==

For deploying an Embedded System, one of the most important configuration is the ''Network Interface configuration''. 

Once the Embedded Device is finally configured for stand-alone bootstrap, the network interface should be configured for reaching the device remotely via network connections like ssh, telnet, ftp, http, 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.debian.org/doc/manuals/debian-reference/ch05.en.html#_the_basic_network_configuration_with_ifupdown_legacy Debian - The basic network configuration]
* [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 device '''192.168.1.100'''

=== 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 the following paragraphs. In the event that there are another network interface, then this must be create/edit as '''/etc/systemd/network/20-eth1.network'''.
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 ====
SBC ORCA has two network interfaces, below is shown how to configure them both through a static IP. In the case of SBCX MINI there is only one ethernet interface, consequently going to configure only eth0 interface.

Example for ethernet interface 0.
<pre>
[Match]
Name=eth0

# Prevent the interface loading if the kernel boots from nfs
KernelCommandLine=!nfsroot

[Network]
Address=192.168.1.100
Gateway=192.168.1.254
DNS=192.168.1.1
</pre>

Example for ethernet interface 1.
<pre>
[Match]
Name=eth1

# Prevent the interface loading if the kernel boots from nfs
KernelCommandLine=!nfsroot

[Network]
Address=192.168.1.101
Gateway=192.168.1.254
DNS=192.168.1.1
</pre>

Once modified, the <code>networkd</code> service should be resarted:

 systemctl restart systemd-networkd

==== Dynamic IP addres (DHCP) ====

SBC ORCA has two network interfaces, below is shown how to configure them both through DHCP. In the case of SBCX MINI there is only one ethernet interface, consequently going to configure only eth0 interface.

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:

<pre>
[Match]
Name=eth0

# Prevent the interface loading if the kernel boots from nfs
KernelCommandLine=!nfsroot

[Network]
DHCP=yes
</pre>

In the event that there are another network interface, the configuration file as the following:

<pre>
[Match]
Name=eth1

# Prevent the interface loading if the kernel boots from nfs
KernelCommandLine=!nfsroot

[Network]
DHCP=yes
</pre>

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@desk-mx8mp:~# systemctl restart systemd-networkd.service
</syntaxhighlight>