You can configure the Login window in several ways:
Enable the Automatic Login mode.
Control how user accounts appear in the window.
Disable the Restart and Shutdown buttons.
Show or hide the password hint.
When you started Mac OS X for the first time, you were in the Automatic Login mode. In this mode, you don't have to enter login information; Mac OS X does it for you. This means that you don't have to enter a username and password each time that you start or restart your machine; the machine starts up just as Macs running previous versions of the operating system do.
You should enable Automatic Login mode only if you are the only person who uses your Mac. If you enable Automatic Login mode with the Administrator account, you provide access to many of your system's resources; this is an unsecured way to operate. However, if you have a Mac in a secure location and are the only person who uses it, the Automatic Login mode eliminates the need to log in every time you start or restart the machine.
If you are going to enable Automatic Login mode, create a non-Administrator account to use. That way, even if someone does get access to your Mac, they won't be able to use the Administrator account. Of course, you might have to log out and then log back in as the Administrator, but this strategy provides a good compromise between security and convenience.
To configure the Automatic Login mode, use the following steps:
Open the System Preferences utility.
Click the Accounts icon to open the Accounts pane of the System Preferences window.
Click the Set Auto Login button. The login account sheet will appear. By default, the username of the currently logged in account will be entered. If you want to have the current account logged in automatically, skip to Step 5.
If you aren't logged in as the Administrator, you will have to authenticate yourself before you can make these changes (click the Lock icon, enter an Administrator User Name and Password, and press Return).
Enter the username for the account into which you want to be logged in automatically in the User Name field.
Enter the password for the account that you want to be automatically logged in when the Mac starts up.
When you have entered the user account information, click OK to enable automatic login. When you return to the Accounts pane, you will see the "Log in automatically as username" check box where username is the account you selected in Step 4.
The next time you start or restart your Mac, the account you specified will be automatically logged in and you will move directly to the desktop for that account.
This setting affects only the start or restart sequence. When you log out instead of shutting down or restarting, you will still see the Login window again and will have to log in to resume using the Mac.
To disable automatic login again, uncheck the "Log in automatically as username" check box on the Accounts pane.
You can configure several aspects of how user accounts appear in the Login window.
Open the Accounts pane of the System Preferences utility.
Click the Login Options tab.
To display empty Name and Password fields in the Login window instead of a list of the user accounts you have configured, click the "Name and password" radio button. When this button is selected, you have to type the short name and password for an account to log in to it. To display the list of user accounts, click the "List of users" radio button instead.
Quit the System Preferences utility. The next time the Login window appears, it will reflect the changes you made.
If you enable Automatic Login mode, you might run into trouble if you leave the Restart and Shut Down buttons enabled. Here's how that could happen. Say you are using your Mac, and decide that you want to take a break for a while, but there are people in your area whom you don't want to be able to use the machine while you step away. You log out, and your machine is protected, right? Not necessarily. If the Restart and Shut Down buttons are enabled, someone can restart the Mac from the Login window and then it would start up in the automatic account giving the person access to the machine. Disabling these buttons prevents someone from using them to access an account that is automatically logged into.
The previous scenario might make you pause to ask a question before you enable Automatic Login mode. If you do disable the Restart and Shut Down buttons and then log out, can someone simply press the hardware Restart or Reset button on the CPU to start up the Mac to automatically log in to the automatic login account? This would bypass the protection offered by disabling the buttons, right? Nope; when the Mac is not shut down properly (by using the Shut Down command), the automatic login feature is disabled when the machine is started or restarted the next time. So, if you have to use one of those buttons, you will have to log in the next time you start or restart the machine.
Open the System Preferences utility, then the Accounts pane, and then the Login Options tab.
Check the "Hide the Restart and Shut Down buttons" check box.
It is likely that there is a bug in the version of OS X I am using, but when I choose this option, the buttons are not actually hidden, but are disabled. At some point, Apple will likely change the name of the button to reflect the true behavior or make the behavior match the radio button name.
Quit the System Preferences utility.
When the Login window appears, these buttons will be inactive; the only way to use the Mac will be to log in under a valid account.
When you created a user account, you were able to enter a password hint. By default, this hint will appear if the user is unsuccessful in logging in after three attempts. If you don't want these hints to be shown, uncheck the "Show Password Hint After 3 Attempts to Enter a Password" check box in the Login Options tab of the Accounts pane in the System Preferences utility.