⚡ Set only hostname

For example, n1

sudo hostname n1
echo n1 | sudo tee /etc/hostname

Edit /etc/hosts, and add n1 for 127.0.1.1

127.0.1.1 n1

⚡ Set fully qualified domain name

For example, n1.iany.me

sudo hostname n1
echo n1 | sudo tee /etc/hostname

Edit /etc/hosts, and add both n1 and n1.iany.me for 127.0.1.1

127.0.1.1 n1 n1.iany.me