I have a 13.3" mid-2012 2.5 GHz Macbook Pro and wanted to upgrade the internal HDD from the factory standard 500GB capacity to a 1TB. I popped the bottom case, discharged any static, undid the screws on the drive bracket, pulled the old drive and installed the new drive.

After putting the Macbook back together, I booted from a USB thumb drive and launched disk utility. In DU, I can see the thumb drive, but I can't see the new hard drive at all. Booting from Internet Recovery is the same.

What's more, I repeated all of these steps on a different Macbook, and the results were the same there -- drive not seen. Bad drive right out of the box, yeah? Rare, but it happens.

So I got a new drive, same capacity, different brand and same result: I don't see the drive in Disk Utility at all, no matter how I boot.

I was thinking that these drives just needed to be formatted, even though both indicated they were Mac compatible, which I presume means pre formatted in FAT so both Mac and PC could read them. Is it possible that these drives are shipped raw and totally unformatted (first was Seagate STBD1000100, SATA III, second is Western Digital WDBMYH0010BNC-NRSN, SATA II)?

If they are indeed unformatted, how the heck am I supposed to format them when Disk Utility can't see them at all? I don't have an external drive available, but I suppose I can wrangle one with some shenanigans.

  • They are unformatted but should still be seen in Disk Utility afaik.
    – emotality
    Commented Jul 25, 2016 at 4:59
  • Boot disks for Mac OS must be format as a Mac OS X Extended (Journaled) disk using a GUID Partition Table format. FAT formation will NOT work for a boot disk.
    – kenjikato
    Commented Jul 25, 2016 at 9:12
  • As @emotality points out, a drive should be recognized regardless of format. Turns out I had not one, but two Macbooks with intermittently failing internal drive cables. A trip to the Genius bar later and I'm up and running.
    – MarsAtomic
    Commented Jul 27, 2016 at 4:34

1 Answer 1


You need to create a boot installer disk to setup a new disk as an internal boot disk for a Mac. You will need a running Mac system and a blank USB Thumb drive (at least 8GB in size). As long as you have that, here are the basics:

  1. Download the OS X installer from the Mac App Store. Quit the installer if it opens automatically after downloading.
  2. Mount your USB flash drive, or external drive with a 8GB or larger partition.
  3. Open the Terminal (which is in the Utilities folder of your Applications folder.)
  4. Use the createinstallmedia command in Terminal to create the bootable installer.

WARNING! This process will ERASE the USB thumb drive, so you can't have anything on it!

For El Capitan the command line would be as follows, where MyVolume is the name of your USB disk:

sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app

Also note that FAT formatted drives will NOT work as a Mac OS boot disk. They must be reformatted to Mac OS X Extended (Journaled) disk using a GUID Partition Table.

To learn more you can head over to Apple's website and read how to Create a bootable installer for OS X. As well as check out a simple walkthrough over on MacWorlds website on formatting a Mac boot disk.

  • I appreciate the response. That article does indicate that I should be able to see the new drive in DU however. I'll try the bootable installer but the fact that neither machine recognizes either of two factory fresh drives does not bode well for my chances.
    – MarsAtomic
    Commented Jul 25, 2016 at 13:57

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .