Originally Posted by samalchow
What will that do?
It will move the passwords out of /etc/passwd, and into a file called /etc/shadow. /etc/shadow is normally much more restricted than /etc/passwd, so people can't get the passwords and try a dictionary attack on them.
If this is your own machine, I'd recommend it - it's much more secure.
If this machine doesn't belong to you (belongs to the company, for example), get the ok before doing it. I can't imagine any company knowingly NOT using shadow passwords, but still not a good idea to change things without warning them.