Please help. I wanted to install linux so I follow this guide: http://www.ubuntu.com/download/desktop/create-a-usb-stick-on-mac-osx I used my external hard drive to do this but then after I finished everything, when I plugged in my external hard drive I get "The disk you inserted was not readable by this computer" and I cannot see my external hard drive in Finder, but I could see it in the Disk Utility. Does this mean all my data was erased? How do I get my external hard drive back? Thank you.

3 Answers 3


Well, if you had data already on the drive, it's gone. You could use a data recover, or ship it off somewhere. But, I'll just go into formatting the drive.

A. Sorta. Generally Linux uses a diffrent type of format for drives (ext4, and a couple others) so it could be that it did work, and your Mac just can't read it. B. If it really did get messed up (you can't boot it into it) then :

  1. Go to Disk Utility.
  2. Click on your drive.
  3. Click on the "Erase" tab.
  4. If you'd like to, enter a name for the drive. Or, just keep it as Untiled if you'd like to try Linux again.
  5. Select a format type, if you'd like to. Fat works best for cross-device compatibility.
  6. Click the "Erase" button.
  7. Get some coffee, or water, depending on the size of your drive.
  • Ah. I didn't see that you had finished the installation. Sorry about that!
    – Spotlight
    Nov 2, 2014 at 21:38
  • Hey thank you very much for helping me. I don't have my Mac with me right now but I really want to know what step 7 and 8 did to my external hard drive? Thanks. Nov 2, 2014 at 22:57
  • @user2649966 I'm guessing you meant from the Ubuntu guide. What it did is it unmounted your drive from your computer, and overwrote all the data on the drive with the Ubuntu image. Data recovery is not impossible from this position (nothing was zeroed out), but it'd be harder since somethings were written.
    – Spotlight
    Nov 2, 2014 at 23:08
  • Thanks again. So it unmounted my external drive but how did it overwrite all the data on the drive when its already unmounted? If its overwritten, how do I get my data back? I have about 300gb of data on there. I can see my external drive in disk utility but not in my finder? Nov 2, 2014 at 23:21

The instructions from Ubuntu are for creating a bootable USB thumb drive for trying and installing Ubuntu. They aren't really meant for making a persistent running installation - doing an installation is one of the options when booted from the thumb drive. If you followed the very last instruction in the guide you linked and were not given the option to boot from the disk, then either your Mac doesn't support USB boot or you ran into a restriction of the EFI firmware. awesomebing1 is spot-on regarding why your external drive is unreadable and for the steps to reclaim the drive, but if there was data already on it, consider it lost.

  • Well I followed the very last instruction and was given the option to boot from the disk. I was able to finish installing Ubuntu and everything but it's just that when I went back to use to external hard drive, my Mac just couldn't read it. Thanks for the answer btw Nov 2, 2014 at 17:32
  • Ubuntu uses the ext4 format for partitions and your Mac will not be able to read it without third-party utilities like the (now-defunct) MacFUSE. You could reclaim a portion of the drive for use on your Mac by using gparted under Ubuntu to shrink the ext4 partition Ubuntu is using, create a new DOS partition with the reclaimed space, then erase and reformat that partition to HFS+ with Disk Utility on the Mac side.
    – douggro
    Nov 2, 2014 at 17:39
  • Hey Thanks for replying. So I tried plugging in my external HDD while using Ubuntu and I was able to see the files. Unfortunately I only see Ubuntu stuffs on it; folders like install, boot, etc.. Did I just wipe all my data? How can I recover it? I have about 300gb of data on it. Please. Nov 5, 2014 at 7:55
  • The partition map has been overwritten and new data written to the drive. Recovery options are slim. Best bet is a professional recovery service but that is very expensive.
    – douggro
    Nov 5, 2014 at 14:47

"UNetbootin for Mac OS X can be used to automate the process of extracting the Ubuntu ISO file to USB, and making the USB drive bootable. The resulting USB drive, however, can be booted on PCs only. If attempting to make a USB drive that can be booted from a Mac, follow the instructions below." - Ubuntu.com website

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