Macs and Ubuntu (I think) do not allow you to su -, you have to use sudo. Apparently this is a good thing.
You can use sudo passwd root to set a root pw and that allows you to do su -

My questions are:

How do you remove the ability to su - so you go back to having to do sudo all the time?

Why is it viewed as a "bad thing" to have su - enabled?

su is a binary (e.g. a file in /bin/su on some systems). You could move this binary to something like /bin/secret_su or a cryptic name then create a wrapper script named su in its place. In the wrapper script you check to see see if the su command was called by sudo and if so you have it execute secret_su - if not you issue a message and exit something like:
Error: You must use 'sudo su' rather than just 'su'.

The reason why use of sudo is considered (by some) to be better is that sudo logs everything it does so theoretically you can see who did what on a system. If this is important to you then you should insure you're sending logging to another server to prevent someone who became root from simply deleting the logs to hide their tracks. In many distros "sudo su" is NOT required.

1 members found this post helpful.

First of all, Ubuntu "allows" you to do anything you want. Some users prefer sudo and some users prefer su. Linux is all about choice and freedom.

Second if you have enabled the root account, but change your mind and want to lock it, so that sudo is the only method:

For more info:
https://help.ubuntu.com/community/RootSudo

1 members found this post helpful.

Hey thanks. BTW It wasn't a sleight against ubuntu, it is just because the default setting on an ubuntu server I used was like a mac in having the su - disabled.
Thanks for the help.