Scenario: you installed ESX. You need to ssh into it, but you don’t have monitor and/or keyboard — and the default ESX settings don’t allow ssh to root.
Solution: connect with VI client. Go to the “Users” tab. Add a user “foo”. SSH into the ESX as foo. Use “su -” to become root. Edit /etc/ssh/sshd_<something> to say “PermitRootLogin yes”. Do “service sshd restart”.
This is it — you can now ssh into the ESX as root.