I made the biggest mistake of my adult life and installed Yosemite without backing up my HDD. Fortunately, I do have most of my actual files and programs saved to my external HDD, but that leads to another problem.

I use a lot of 3rd party apps to make music, and they are not compatible with 10.10 i.e. Pro Tools etc. I formatted my HDD in an attempt to start over but it keeps reinstalling Yosemite from the Internet.

I've made several USB boot drives but when they go to load up it just gives me "international no" sign (see image below).

Can someone please help me as my work/life is tied in to my studio. Oh also my external HDD is now all of a sudden read-only NTFS instead of Mac read/write enabled.

Screenshot of OS X when cannot boot off of a USB


3 Answers 3


The Booting from USB issue

Ok, so first off. I don't know how you made the bootable USB, but for the sake of consistency in my answer I will give you a method to use:

  1. Download Mavericks for the App store. (I checked, it is still there for downloading)
  2. Plug in the USB drive you want to boot from (has to be 8GB or more)
  3. Then from the Terminal app run this command:

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

It takes a while to complete so go make yourself some coffee and let Mac OS do it's thing.

NB Notes:

  1. Replace MyVolume with the name of your USB drive.
  2. If you have already downloaded Mavericks and backed it up somewhere, you can just copy it back into the Applications folder. It has to be called Install OS X Mavericks.app.

Taken from Creating a bootable OS X installer in OS X Mavericks.

If you boot your Mac, immediately hold down the ALT key and select the USB as the boot device. This should boot into the Mavericks installer. From there you can run DiskUtilities and partition you OS hard disk and install Mavericks.

The NTFS issue

It sounds like you might have had a 3rd party app like Paragon installed. Mac does not natively allow writing to NTFS.

  • 2
    Please do not use link shorteners. If the link shortening service goes down, the link will be lost.
    – tubedogg
    Commented Oct 27, 2014 at 10:14
  • ok, good point!
    – Dewald Els
    Commented Oct 27, 2014 at 10:48

You need to make sure that you are using the correct build for your iMac.

In this document: http://support.apple.com/kb/ht1159 you can find the exact build for your iMac, then you have to make sure that you are using a 10.9 version after the minimum build your computer requires. In case you have trouble with that, I find that the best way is to "buy" mavericks from a similar computer and then create the install disk using Disk Maker: http://liondiskmaker.com/

After that the computer will reboot from this installation disk and you will be able to install 10.9, but you cannot transfer information from your old hard drive, since migration assistant cannot migrate from an older version, so you will need to do the migration manually, which basically is copying folders from your old drive or backup, to your new drive.

Please let me know if you have any doubts I did not want to extend myself much and take for granted that you are familiar with many of the procedures.


It sounds like your goal here is to get back to a working system running Mavericks rather than Yosemite, so that your apps will run and you can access your documents and get on with your life. If you have a working computer, albeit running Yosemite, you should be able to download an installer for Mavericks (in my case I can get that from my list of purchased apps in the App Store). With that you should be able to do a clean install of Mavericks. Then you can copy across all your backed up files and apps. You might need to reinstall some of the apps, but essentially you should then be where you need to be. Then make a bootable clone of your system, using something like SuperDuper. Then you can run some checks to find out when your critical apps will be updated to support Yosemite, and schedule an update at a suitable time.

  • 1
    please edit the download links. The techspot link leads to the 10.9.5 updater/combo updater which won't help much and the apple support site doesn't offer mavericks. only the app store might do this if you've "bought" it previously there
    – klanomath
    Commented Oct 27, 2014 at 10:12
  • Thanks for pointing out the error. i've now corrected that.
    – Graham
    Commented Oct 27, 2014 at 13:28

You must log in to answer this question.

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