EC2 instance root password reset

I have an AWS account running a Ubuntu image. I want to change the root password on the instance, but 1) I don't recall it , and 2), i received the following failure when attempting to do so:

[cloudshell-user@ip-10-6-67-43 ~]$ sudo passwd root

sudo: passwd: command not found

In fact, nowhere on this E2C instance of Ubuntu does there exist a binary labelled "passwd"

Any clues?