Also, since you've changed the UID of root2 to the one of root, it changed the password of 'root' since that was the 'right' uid.
root2 didnt get the password update, since it has another original uid.
To avoid such disasters, i'd suggest to use these tools (as root obviously, and with care):
- useradd
- userdel
- usermod
- groupadd
- groupdel
- groupmod
Read their respective
--help output.
Or go GUI either way
system-config-users.
Hope this helps