Unlike Raspbian, when system is first flashed with Ubuntu MATE it’s not possible to SSH into the machine out of the box. The problem with a Ubuntu MATE is that it requires you to have a monitor, keyboard and mouse for the first boot — as the graphical installer (ubiquity) awaits to complete the initial process (language, keyboard, user account, then probably the SSH key generations). At this stage, SSH is not configured and even if it was running, there is no account to connect as (root is disabled by default).
Setting up SSH
Enter the below commands after you have finished setting up Ubuntu MATE:
sudo apt-get update sudo apt-get install openssh-server sudo ufw allow 22 sudo /etc/init.d/ssh restart
Enabling SSH on boot
After completing the installation of openssh we now need to make sure the SSH daemon starts automatically at the boot time. We can use the “systemctl” command to add the ssh daemon init script to your system startup using the following command:
sudo systemctl enable ssh