My first Linux distro was Ubuntu 17.10. After the installation, I tried to add a PPA. I typed password but nothing happened. No cursor move, no bullets or asterisks. I thought, something went wrong. I closed the terminal and repeated this process again and again. after few attempt, I typed the password and clicked on ENTER button by luck and installed the PPA.
Now I realized , it is a security mechanism to prevent the others near the user to guess the password length. But this is confusing for new users. If possible, give a hint that " password will invisible " in the terminal.