外部からssh許可

sudo ufw status
sudo ufw enable
sudo ufw allow 80
sudo ufw allow 443
sudo ufw allow from 192.168.100.0/24 to any port 22
sudo ufw allow ssh
sudo ufw reload
sudo apt-install openssh-server
sudo nano /etc/ssh/sshd_config

32行目
#permitRootLogin prohibit-password
↓
permitRootLogin no

sudo systemctl restart ssh