在Mac OS X中启用root用户
http://support.apple.com/kb/ht1528
1. From the Apple menu choose System Preferences....
2. From the View menu choose Accounts.
3. Click on the lock and authenticate with an administrator account.
4. Click Login Options....
5. Click the "Edit..." or "Join..." button at the bottom right.
6. Click the "Open Directory Utility..." button.
7. Click the lock in the Directory Utility window.
8. Enter an administrator account name and password, then click OK.
9. Choose Enable Root User from the Edit menu.
10. Enter the root password you wish to use in both the Password and Verify fields, then click OK.
太复杂了...
最简单的办法：
sudo passwd root
Mac下的用户管理命令:
dscl （Directory service command line）