At this point I'm just trying to get a copy of my hard drive before I wipe it.

I have an iMac running El Capitan and I am unable to login to my user account (spinning wheel of death).

I've tried to start up in Recovery Mode and backup files using Disk Utility. After waiting several hours I got the error message "The operation couldn't be completed. (com.apple.diskutililty error 3.)"

This was the process I followed.

When I try to re-install a new copy of El Capitan I get the error "Unable to install because this disk has S.M.A.R.T errors"

What else can I try?

How can I create a backup of my hard drive?

  • Have you ran a hardware test yet? Your drive could be done.
    – bret7600
    Commented Nov 6, 2016 at 19:17
  • Also, starting from safe mode might allow the backup of files. support.apple.com/en-ca/HT201262
    – bret7600
    Commented Nov 6, 2016 at 19:29
  • Since the HDD has S.M.A.R.T errors I wouldn't try creating a image of the entire Macintosh HD and just one of your Home Folder to start, as that I'd assume contains the most important files. If it makes it through your Home Folder I'd do the Applications Folder. Then once the HDD is replaced and OS reinstalled along with your Data then start using Time Machine! ;) Note that I'd actually boot the Mac from an external drive that had OS X/macOS installed and use it to make the image from and not boot the Recovery HD from the internal failing HDD. Commented Nov 6, 2016 at 19:53
  • I believe it is my Harddrive that is slowly dying. @user3439894 Thank you this does seem to be working but it is working VERY slowly. It's been 3 days and all i've been able to successfully grab is my desktop and photos. It seems that some of the folders start to back up and then it fails, while others seem to work (only after hours of trying). I think I am going to buy a new harddrive and replace it and try to back up the old HD externally. Can you show me where I can get info about booting the mac from an external? Thanks for everything Commented Nov 11, 2016 at 17:22

1 Answer 1


Have you tried starting your iMac in Target Disk Mode?

To do this, switch off your iMac and then boot it up again making sure to hold the T key down until you see an icon appear on the screen.

If that works, then you may be able to use this mode to access your Hard Drive from another Mac (or even a Windows PC). However, if using a Windows computer it has to have the right connections and also be able to read a Mac's drive, usually by having extra drivers such as MacDrive, TransMac, MacDisk, or HFSExplorer installed.

Speaking of connections, you didn't specify what model of iMac you have. Typically you would use an appropriate cable connecting the two computers via your FireWire or Thunderbolt port. USB is not supported.


In a nutshell, if you can get your iMac to start in Target Disk Mode, you can connect it to another computer (almost always another Mac) and your iMac's hard drive will then appear as an external drive on the other computer. If so, copy whatever files you can from it to another drive.

I should warn you though that it sounds as if your hard drive has failed, and doing this may not work. Also, even if it does, I wouldn't try reformatting it to continue using it. You really should replace the drive or use an external drive as your bootable drive.

Also, if you can boot from an external drive, another option is to just do that and try copying across your data that way (i.e. From the internal drive onto another drive). This avoids the need to try using Target Disk Mode.

  • I believe it is my Harddrive that is slowly dying. I think I am going to buy a new hard drive and replace it and try to back up the old HD externally. Can you show me where I can get info about booting the mac from an external? Thanks for everything Commented Nov 11, 2016 at 19:02
  • Booting your iMac from an external drive is extremely easy. On startup press the Option key down until you see hard drive icons appear on the screen. Select the icon representing the external drive and press Enter. If you then want your iMac to always boot up from the external drive, once you've booted up you can go to System Preferences > Startup Disk and select the external drive. Note: For all this to work you need to install macOS onto the external drive first. You may also want an external drive that is USB powered so you don't need a separate power source, but that's personal preference.
    – Monomeeth
    Commented Nov 11, 2016 at 21:07
  • Also, if you intend to always boot up from an external drive you may want to consider investing in a hard drive enclosure that has a FireWire or Thunderbolt connection (depending on what your iMac supports). You'd then need to purchase just the hard drive (preferably a 7200rpm model) and placing it inside the enclosure. This option would ensure you have a fast external drive since it'd become your main boot drive. This would, however, most likely need its own power supply. Any decent computer shop should be able to help you.
    – Monomeeth
    Commented Nov 11, 2016 at 21:19

You must log in to answer this question.

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