Power User Mac Disk Tricks

by steve on November 29, 0000

This is for you Mac OS X heads out there.  The GUI Disk Utility app is perfectly fine for most situations where you’re formatting and working with hard drives, volumes and partitions.  But what about if you’ve managed to give your drive some kind of terribly unspeakable formatting damage and Disk Utility and other GUI tools can’t seem to fix it.  You’re pretty sure there’s nothing physically wrong with the device.  This happened to me recently.
I’d found a way to bend the rules and get a FAT32 and an HFS+ partition on a drive in such a way that I could use it just fine in OS X and Windows XP.  Hooray, right?  Well, it seemed clever until it stopped working and nothing would fix the disk.  So fine, I wanted to reformat it, but the OS X tools didn’t like the MBR (Master Boot Record) I’d squeezed on there.

Enter diskutil.  This is a UNIX command line tool you run from the terminal.  From the command line you can do a bunch of things you can’t do from GUI.  Here’s a good run down of how to use it:


diskutil eraseDisk HFS+ mydiskfixed disk3

…and my hard drive was usable again.

While you’re at it, you can also create and edit partitions from the command line as well using pdisk:


I have not personally needed to use pdisk yet, but the day will come.

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