If you need to find the motherboard model of your system from the terminal or command line and you do not want to take off the case, there is a program that comes with Ubuntu by default that can do this: dmidecode

If you do not have it, you can install it with this command in most Debian based distributions (Lubuntu, Debian, Mint):

sudo apt-get install dmidecode

To find out your motherboard model, run this command:

sudo dmidecode -s baseboard-product-name

To find more details about your motherboard, run this command:

sudo dmidecode -t baseboard

To find details about all the hardware on your system, run this command:

sudo dmidecode