Linux
Reset root password
sudo passwd root
Allow root ssh login
sudo grep -q '^PermitRootLogin' /etc/ssh/sshd_config
&& sudo sed -i 's/^PermitRootLogin.*/PermitRootLogin yes/' /etc/ssh/sshd_config
|| echo 'PermitRootLogin yes' | sudo tee -a /etc/ssh/sshd_config > /dev/null
&& sudo systemctl restart sshd