How to boot Mac OS X in Single User Mode?

[ravindar]

How do I boot Mac OS X in Single User Mode?


Start or restart your Mac.

Hold down the Command (Open Apple)-S keys

Enable Mac OS X Firmware Password

Please reselect your startup device PRIOR to resetting your PRAM or Open firmware.

The following firmware configuration is supported on:

All Intel-Based Macintosh Computers

iMac (Slot Loading) and later models of G3 iMac
iMac (Flat Panel) and later models of G4 iMac
iMac G5 and later models of G5 iMac
iBook – all models, both G3- and G4-based
eMac – all models
PowerBook (FireWire)
PowerBook G4 and later models of G4 PowerBook
Power Mac G4 (AGP Graphics) and later models of G4 Power Mac
Power Mac G4 Cube – all models
Power Mac G5 and later models of G5 Power Mac
Open Firmware password protection disables the following features:
Depressed N-key boot – Boot from NetBoot server
Depressed T-key boot – Boot in Target Disk Mode
Depressed C-key boot – Boot from CD/DVD or other designated optical drive
Command V boot – Boot in Verbose Mode
Command S boot – Boot Single User Mode
Command+Option-P-R Combination boot – PRAM Reset
Command+Option-O-F Combination boot – Use of Open Firmware Interface commands without a password. – Not available on Intel-based Macs
Option key boot – Use of Startup Manager without a password
Enabling the Open Firmware Password
Obtaining the Software
Mac OS X 10.4 and higher
Download the Open Firmware Password Application from here: Open Firmware Password.
Mac OS X 10.1 – 10.3.9
The Open Firmware Password Application Utility is located in the /Applications/Utilities/ folder on your software installation DVD. Please copy it to your machine.

Configuration

Launch the Open Firmware Password Application.

Click the authentication icon and enter your Administrator credentials. You will be prompted for a password.
Locate and click the Change button.

This will launch an Open Firmware Password window.

In the Open Firmware Password window, locate and click to select/check the "Require password to change Open Firmware settings" option.
Enter your Administrator password.

Retype your Administrator password in the box entitled Verify.

Click the OK button to commit your password and password verification information. This will prompt a confirmation window.

Locate and re-select the lock icon.