First, I must apologize for confusing Safe Mode with Single User Mode.
Booting in Single User Mode and Running fsck -y:fsck (file system check) is a start-up Unix utility ran from the command line.
Here is Apple's technical article on running FSCK.
Apple tech article states that Disk Utility Repair Disk is the same as running as fsck, yet many users have said they prefer fsck -y from a Shut Down. In the linked Apple tech article, Apple states, "For Mac OS X 10.4 or later, you should use Disk Utility."
In any case, we do NOT need an Apple boot Install CD or DVD to run fsck -y.
Here's how to fsck -y:
Shut Down Mac completely, Restart your Mac.
Immediately press and hold down the Command and S keys until text begins to scroll on screen. In a few more seconds, the Unix command line prompt (%).
Type fsck –y (fsck space minus y).
Press Return key.
Text will start updating the progress...if there is damage, the final line will say ***** FILE SYSTEM WAS MODIFIED *****.
If you see that message, REPEAT Steps 3 and 4 again and again until that message no longer appears. Having to run fsck more than once is normal, because the first run's repairs may uncover additional problems.
The end should read: "The volume <name of disk> appears to be OK."
Then type "reboot", then press Return to boot back off the hard drive.