As you saw in the dev kit Getting Started Guide in the “Discovering Galileo IP Address” section, if the Galileo board is connected to a network or even to another computer that has Internet access, the system is capable of assigning an IP address automatically.
On rare occasions, you may have to assign a static IP address. In this case, use the ip Linux command. The ip command below assigns the IP address 169.254.8.17 to the Ethernet interface (enp0s20f6), with netmask 255.255.255.0 (/24):
$ systemctl stop connman $ ip addr add 169.254.8.17/24 dev enp0s20f6
For more information, refer to the online documentation for ip at this link.