Apple Mac OS X FAQ
Monday, October 21, 2002
Red Items in Force Quit
I've had occasion recently to have a to force quit an application and have noticed that occasionally some of the applications that are running are listed in red. What does that signify?
Red items are "not responding". Thus probably a good candidate for a force quit.
Using Disk Utility and fsck for File System Maintenance
When the computer cannot start up normally, you may need to use a disk repair utility. Mac OS X includes two such utilities, Disk Utility and fsck. This document describes how and when to use each.
In some situations, file system errors may prevent the computer from starting up to a normal state. This could occur after improper shutdown, forced restart, or power interruption. These symptoms indicate that you should use a disk repair utility:
1. Partial start with command line
The computer starts up partially then pauses in a command-line (text only) environment. A message such as "file system dirty, run fsck," may appear. Below the message, there is a command line, indicated by a pound-sign prompt (#). Commands you type in this environment appear next to the prompt. When this happens, you should run fsck from the command line.
2. System starts up partially but does not display a command-line prompt.
The computer may start up but fail to reach the login screen; or it may reach the login screen but fail to reach the Desktop after the user name and password are entered. In this case, you must start up in single-user mode.
I. First, try a Safe Boot
Mac OS X 10.2 and later include the Safe Boot feature. If you have not yet upgraded to 10.2 or later, then skip to Section II. A Safe Boot may allow you to restart successfully using a reduced version of system software. During this restart, an automatic disk check and repair may resolve your issue. If it does, then you will not need to take any further action. Follow these steps to see if a Safe Boot will resolve your issue:
1. Restart the computer (using the Power button or Reset/Interrupt button if necessary).
2. Immediately after the system startup sound, press and hold the Shift key until "Safe Boot" appears.
Note: There may be a considerable delay, particularly on larger startup volumes, since the disk check and repair take place before "Safe Boot" appears.
3. After the system is fully started up, restart again normally.
If the restart is successful, you do not need to do any more troubleshooting, unless the issue recurs.
II. Next, Try Disk Utility
In most circumstances, you should perform disk verification and repair using the Disk Utility application included with Mac OS X.
Steps for using Disk Utility:
1. Insert your Mac OS X CD-ROM disc, then restart the computer while holding the C key.
2. Once started up from CD, choose Disk Utility from the Installer menu.
Important: Do not click Continue in the first screen of the Installer. If you do, you must restart from CD to access Disk Utility.
3. Click the First Aid tab.
4. Click the disclosure triangle to the left of the hard drive icon to display the names of your hard disk volumes and partitions.
5. Select your Mac OS X volume, if necessary.
6. Click Repair.
Disk Utility checks the disk.
You should always start up from CD to use Disk Utility.
If the Verify and Repair buttons are dimmed in the Disk Utility window, be sure you have selected a volume to check.
III. When to use fsck instead
Using Disk Utility while started up from CD eliminates the need to use fsck, but there are situations in which fsck may be necessary. For example:
* Your Mac OS X CD is not immediately available.
* Your CD-ROM drive is not immediately available.
The fsck utility may be able to verify and repair a disk in such a situation.
About the command line interface (CLI)
The fsck utility is run from the command line. This means that you must type a text command at a prompt (#), rather than using the mouse pointer to open an application. Examples of a CLI are the Terminal application and single-user mode. You should start up in single-user mode to use fsck.
How to start up in single-user mode
1. Restart the computer.
2. Immediately after the startup sound, press and hold both the Command (Apple) and "s" keys on your keyboard. The computer will display a series of text messages, at which time you may release these keys.
When the computer has started up, it will display a command line prompt (#). The computer is now in single-user mode.
Note: If necessary, perform a forced restart as described in the Emergency Troubleshooting Handbook that came with your computer. On desktop computers, this is generally achieved by pressing the reset/interrupt button, which is marked with a triangle. On portable computers, this is generally achieved by pressing the Command-Control-power keys. If a portable computer does not respond to this method, you may need to reset the power manager.
IV. How to Use fsck From the Command Line
Once you have reached a command line, follow these steps to use fsck:
1. At the prompt, type: fsck -y
2. Press Return.
The fsck utility will go through five "phases" and then return information about the disk's utilization and fragmentation. If fsck alters, repairs, or fixes anything, it will display the message:
***** FILE SYSTEM WAS MODIFIED *****
Important: If this message appears, repeat the "fsck -y" command until this message no longer appears. It is normal for your computer to require several "passes" of fsck, because first-pass repairs may uncover additional errors.
3. When fsck reports that no problems were found, type: reboot
4. Press Return.
The computer should start up normally and allow you to log in.
This extra information is provided for users interested in UNIX-style command-line syntax.
The -y flag:
This tells fsck that you want to answer "yes" to all questions about fixing, repairing, or salvaging information. This is the optimal approach, as answering "no" to any question causes fsck to stop. You cannot determine that all necessary repairs have been made until fsck completes and gives its final report.