Respectfully, you could install it by creating the symbolic link yourself?Correct on that part.
Incorrect with that part.
1. You can't install it because
2. It is a symbolic link to another command, eg systemctl
Try typing
Code:man shutdown
and you will get the usage.
The default timeframe with just sudo shutdown (or shutdown as root) is 60 seconds, described as "+1" in the manual.
Bear in mind, too, that Rob wrote this tutorial 10.5 years ago, so cut him some slack with -h not being necessary, it undoubtedly changed over the years.
Cheers
Wizard