# How to “scan disk” or “repair disk” by booting up in single user mode and scan disk?

I think when we are using the Mac, we can't choose "Repair Disk" in Disk Utilty to repair the current hard drive, as the drive is being used.

If "Verify Disk" is used, it only takes about 3 to 5 minutes for a 120GB hard drive, so it seems not the whole drive is scanned.

It seems that we can boot up using the OS X Installation DVD and use Disk Utility to do Repair Disk. But is it equally possible to boot up the Mac in a single user mode (or is it called the command line mode), and use fsck or diskutil to do it?

The use is mainly to repair the hard drive (just to double check) that the whole hard drive is ok, after the Macbook is dropped from the bed about 3 feet tall.

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All these programs only check the logical structure of the data on the disk. Checking for physical damage is a different kettle of fish altogether, I think. In other words, if your drive is sufficiently unharmed after the drop that you can still read data from the drive, the contents should be okay. And if not, you'll find out soon enough, without running any tests. –  Harald Hanche-Olsen Jun 15 '12 at 20:59
is that right... so it is different from Windows 7's chkdsk where the empty sectors are scanned too? For example, can't Mac OS X or UNIX try to write 0x00 to the whole sector, verify it, and write 0xFF to the whole sector, and verify it... it can do so not sector by sector, but write 0x00 for all empty sectors and verify it, and write 0xFF for all empty sectores again and verify it –  動靜能量 Jun 16 '12 at 1:12
As far as I know, yes … but I claim no expertise. –  Harald Hanche-Olsen Jun 16 '12 at 8:29