Ranjan Maitra writes:
Btw, is there a way to take out a root password once set?
The manual page for the passwd command describes its options. One option
sets an invalid password which means that the account cannot be logged in
directly, and the only way to do so is via some other means, like ssh public
key authentication. Another option is to remove the password, so that one
can log in as root without entering a password. Be sure to fully understand
the ramifications of either options.
If you have a question about a particular command, the first place to look
is always its manual page.
$ man passwd