Mac OS X in a Nutshell

Starting Up and Logging In

When you turn on your Mac (or restart it), it spends a couple of minutes or so initializing various processes to ready the machine for user login, as well as whatever network service it may provide (see Chapter 7). Unix veterans are used to seeing this phase as a cascade of messages spilling down a text console, but Mac OS X hides all this information behind a plain white screen with a plain gray Apple logo on it.

Tip

You can see all that startup text if you really want to, by booting into single-user mode, as described in Chapter 11. This can be a useful diagnostic tool for hardcore Unix-heads who know what they’re doing, or a way for the merely curious to watch the strange sight of their Mac rolling out of bed and stumbling around in pure-Unix mode before it puts on its Mac OS face. Use the exit command at the single-user shell to resume the normal Mac OS X boot process.

You may also view some of the machine’s startup messages after the fact by looking at the file /var/log/system.log. (Note that only users with admin access can read the file.)

Eventually the system either settles on the login screen, or goes ahead to log in a specific user, depending upon the machine’s configuration. In the former case, you’ve got to provide your username (either by choosing it from a list or typing it in—again, based on configuration settings in the Accounts preference pane) and password before you can continue into the Finder, whereupon you can actually start using the operating system.

Logging in is necessary because of Mac OS X’s Unix-based file permissions system; before you can interact with the system in any way, the machine has to know who you are so that it can tell what files and folders you’re allowed to access, and to what degree. Generally speaking, everything in your Home folder (which you can always go to through the Finder’s Go → Home (Shift-

-H) option) belongs to you, and you are unrestricted in how you read, modify, create and delete the files and folders within it (and the files and folders within those folders, and so on). Everything outside your Home folder is another matter. For example, all users can run the applications stored in the /Applications folder, but only admin users can modify that folder’s contents; and no user, admin or otherwise, has full access to any other user’s Home folder.

See Chapter 9 for more information on the structure of Mac OS X’s filesystem and permissions. Logging in also sets up all of your personal system-interaction preferences, as stored in your Library folder; see Chapter 9.

Startup and Shutdown Keys

For most users, starting and shutting down your Mac is fairly routine: press the Power-on button to start, and go to

→ Shut Down to turn off the machine at night. But there are times when you need to do more, for whatever reason. Table 1-2 lists some of the additional keys you can use when starting, restarting, logging out, and shutting down your system.

Tip

Some of the keyboard shortcuts listed in Table 1-2 will work only on newer hardware. If you are using an older Mac, these keyboard shortcuts may not work.

Table 1-2. Shortcuts for starting, restarting, logging out, and shutting down

Key command	Description
C	Holding down the C key at startup will boot from a CD (useful when installing or upgrading the system software).
T	Holding down the T key at startup will boot from a FireWire drive, if it has a bootable System folder.
X	Holding down the X key at startup will force the machine to boot into Mac OS X, even if Mac OS 9 is specified as the default startup disk.
-S	Boots into single-user mode.
-V	Boots into verbose mode, displaying all the startup messages onscreen. (Linux users will be familiar with this.)
Shift	Holding down the Shift key at startup invokes Safe Boot mode, turning off any unnecessary kernel extensions (kexts), and ignoring anything you’ve set in the Login Items preferences panel.
Option	Holding down the Option key at startup will take you to the Startup Manager, which allows you to select which OS to boot into.
Mouse button	Holding down the mouse button at startup will eject any disk (CD, DVD, or other removable media) that may still be in the drive.
Shift-Option- -Q Option + → Log Out	Logs you off without prompting you first.
Option-Power-on Option + → Shut Down	Shuts down your system without prompting you first.
Option + → Restart	Restarts your machine without prompting you first.
Control- -Power-on button	Forces an automatic reboot of your system; this should be used only as a last resort as it could mess up your system. (Mostly, you’ll just wait forever at the gray Apple startup screen while an fsck happens in the background.)