Configuring Static IP Addresses

It is sometimes desirable to provide static IP configuration for network interface instead of relying on DHCP. Below we describe several methods to do that.

Using /etc/network/interfaces

This is a legacy method with various limitations and we do not recommend using it, especially in combination with network managers. The configuration file /etc/network/interfaces is used by ifup and ifdown tools to perform network interface configuration. In the SystemV init setup ifup and ifdown are invoked by /etc/init.d/networking boot script. In systemd setup /etc/init.d/networking is not available and you should create your own systemd service file that invokes "ifup -a" on startup and "ifdown -a" at shutdown.

If you configure all network interfaces via /etc/network/interfaces, it is better to completely disable the network manager service.

The example below configures eth0

auto eth0
    iface eth0 inet static
    address 192.168.1.100
    netmask 255.255.255.0
    gateway 192.168.1.254
    dns-nameservers 8.8.8.8 4.4.4.4
    dns-search foo.org bar.com

The DNS settings in /etc/network/interfaces rely on the availability of /sbin/resolvconf tool to update /etc/resolv.conf configuration file. If /sbin/resolvconf is not present, rebuild Yocto image after adding the following line to conf/local.conf

IMAGE_INSTALL_append = " resolvconf"

Configuring WIFI via /etc/network/interfaces is not recommended.

Interaction with ConnMan

ConnMan will override the settings in /etc/network/interfaces unless configured to ignore relevant interfaces. For example, after configuring eth0 and eth1 in /etc/network/interfaces, you should create /etc/connman/main.conf and add the following:

[General]
NetworkInterfaceBlacklist=eth0,eth1

ConnMan will also override the contents of /etc/resolv.conf as it includes its own DNS proxy. To prevent that, start ConnMan with the options "-r" or "--nodnsproxy"

Interaction with NetworkManager

NetworkManager will override the contents of /etc/resolv.conf as it uses dnsmasq tool as DNS proxy. To prevent that, create /etc/NetworkManager/NetworkManager.conf and add the following:

[main]
dns=none

Using connmanctl

The ConnMan command line tool, connmanctl, can be used create static IP configuration. To create initial configuration the relevant interface should be connected to the network.

To get the list of connections run

# connmanctl services

For example:

root@imx7-var-som:~# connmanctl services
*AO Wired                ethernet_0eb31468dcc9_cable

Wired Ethernet connections will be shown as ethernet_<mac_address>_cable.

To create static IP configuration run

# connmanctl <service> --ipv4 manual <ip address> <netmask> <gateway>
# connmanctl config <service> --nameservers <dns-addr>

For example:

 # connmanctl ethernet_0eb31468dcc9_cable --ipv4 manual 192.168.1.100 255.255.255.0 192.168.1.254
 # connmanctl config ethernet_0eb31468dcc9_cable --nameservers 8.8.8.8 4.4.4.4

The configuration will be saved in /var/lib/connman/ethernet_0eb31468dcc9_cable/settings.

The downside of this method is the use of non-constant parameters (e.g. MAC address) to identify the connection, which makes it difficult to incorporate the configuration into Yocto image and use it on multiple devices.

Using nmcli

The NetworkManager command line tool, nmcli, can also be used create static IP configuration. In the example below a static configuration is created for interface eth0.

# nmcli con add type ethernet ifname eth0 name static-eth0 ip4 192.168.1.100 gw4 192.168.1.254
# nmcli con mod static-eth0 ipv4.dns "8.8.8.8,4.4.4.4"

The configuration will be saved in /etc/NetworkManager/system-connections/static-eth0. Once generated it can be incorporated into Yocto image and used on multiple devices.