Reformatting an External Hard Drive Mac OS X
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Ok, here's the problem. Someone with a mac has purchased an external hard disk. Being normal Mac users, they don't know very much about hardware, operating systems, computer file systems, etc.

So the disk is plugged in. It appears on the desktop, and it's in Finder. Click on it, the system doesn't complain. But then the moment of truth arrives: the person thinks, ok, now time to transfer my files, or use TimeMachine.

Drag the file to it, nothing happens. No error, no message telling you anything. Just a red circle with with a slash through it. Again, zero error message, just no result from the action. Usability score? 0. Shame on you mac, this is a standard issue, and you should handle this better.

The cause? The hard disk is formatted with NTFS. Mac OS X version the person has does not support write operations to NTFS. Does support read. Since most users have exactly zero idea of read/write differences, permissions, or anything else, the vaunted Mac user friendliness shows a big FAIL here. Shame on you Mac.

So, we have to fix this for our friend, who has been stymied by this fact. But first a bit of speculation. Apple some years ago, during their down years, took a large investment from Microsoft. In exchange for this, they got access to a lot of Microsoft Intellectual property, including I assume the specs to create a driver for NTFS, the standard Windows file system since Windows 2000. Also the standard file system large external disk drives are formatted with. So my suspicion is that Apple WANTS their users to experience this failure, so that they then head off to the local mac store and buy the hardware there, where of course everything 'just works'. I believe, as I extend this forum's how-tos, you will find this a repeating theme when it comes to strange non user friendly issues I have encountered, that are all easily fixable on a technical level.

Ok, enough talk, let's get to work, and fix the issue.

What we need to do is reformat the large disk drive to either a straight Mac OS X native file system, or to a file system that everything will be able to read and write to, for large disks, you'll want to use the exfat that is offered.

I found a very clear how to reformat hard drive in OS X, including nice screen shots, but I'll post the steps here for those who don't need pictures.

How to Format a drive in OS X
This should be a complete set of steps.


  1. Open 'Finder'. Finder is the File System Explorer in Mac OS X. Do that either top menu, 'Finder', or the doc thing with icons, the two faces icon is finder.
  2. Make sure finder has the right view options, I suggest making these default at least for your session: Top menu, click 'View', check 'As List', check 'Show Sidebar' if it isn't checked, to get the left hand system navigation menu.
  3. The menu should now be there. Find the 'Places' section. Click 'Applications'. Scroll down in the right pane to 'Utilities', then open that, and click 'Disk Utility'.
  4. In the new window, find the disk in the right bar, click on it.
  5. This brings up the options for that disk. To reformat the entire disk, click on 'Erase' button. This isn't a very well named or intuitive name, but that's what it is. 'Erase' is really 'Reformat' in all other operating systems.
  6. You will now see two fields, the drop down list is where you pick your file system. Please note, if you will never share this disk with a Windows or Linux system, I suggest you use OS X extended journaled, if you want a file system that is NOT case sensitive, like Windows uses, or pick OS X extended case insensitive journaled if you want one that is like real Unix or Linux. NOTE: I believe to use TimeMachine properly you will need to use a Mac File system to preserve permissions of OSX. If you want to share the disk with other operating systems, then you will want the new exFat file system, that is designed to work on large disks, and supports larger files than 4 gigabytes. More on exFat from MSDN and wikipedia
  7. Also give the new disk a label so you will know what it is when you plug it in. I usually pick a name like: usb500gb-1 so I can see which drive it is, or say: wdusb500gb
  8. Now click the 'Erase' button at the bottom. WARNING: ALL DATA WILL BE LOST WHEN YOU REFORMAT A HARD DRIVE!!!
  9. It will churn a bit, and then the disk will be available for OS X use.


And that's it, the drive that was frustrating your friend and the people who were trying to help him is now available for use on OS X. Remember, if you are going to use this drive as a time machine backup drive, it should be formatted in Mac Extended journaled file system, or case sensitive.
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