My Mac has been running fine until I decided to upgrade to OS X 10.10, Yosemite. When it is installing I get the message:

File system verify or repair failed.

I clicked the restart option to boot into my internal HD but tells me its unavailable. I then rebooted, held Command+R to enter disk utility in order to repair the disk, but it tells me it failed and should backup and restore the HD.

I then tried to create an image on my external drive but this also fails with the message:

Unable to create Macintosh HD.dmg. (Input/output error)

I am stuck in this vicious cycle of restarting and the installation failing. I cannot escape the installation process.

Is there a way to access my files and copy them onto my external HD, then erase and restore the internal HD?

  • Please add the total size and the free space of each of your disks to your question. Do you use TimeMachine to back up your main (internal) drive?
    – klanomath
    Dec 9, 2014 at 12:54
  • I can't recall off the top of my head how much I have available but its fairly new so should be plenty. I do have a bootcamp partition though. I have done a number of backups with TimeMachine however when I go into disk utility and TimeMachine it just got stuck on the searching timemachine back up. Dec 9, 2014 at 13:11
  • is there a way of going into safe mode and obtaining the files I need? Dec 9, 2014 at 13:12
  • Yes, but you have to restart into recovery mode to accomplish that. You may create an image of your internal disk ignoring those errors. But knowing the sizes/free space is essential for this. Restart into recovery mode and open Disk Utility choose the different disks/partitions and make notes of their sizes and the free space of your external disk and then post it here.
    – klanomath
    Dec 9, 2014 at 13:20
  • Be sure to unplug all external devices when you reboot. Dec 9, 2014 at 16:21

3 Answers 3


You could try booting off a Linux LiveUSB to back up your files.

Once that is done, you can reformat your HD and then reinstall OS X.

You should also keep an eye on your HD; these types of errors often suggest that your drive is corrupted or damaged.


Have you got access to another mac? Your best bet would be to connect other mac using target disk mode, either via firewire or thunderbolt. Your internal drive will show up on the desktop of the other mac for you to copy off your files.

Other option would be booting up via an other system via an external drive, open disk utility and try to repair a couple of times. Soon or later your internal drive will pop up on the desktop so you can recover your files. But I stress I need an external hard drive or USB key drive with a OS X system on it to do this.

It's sounds like your hard drive is dying basically, hence why Disk Utility can fix/repair for you to install Yosemite.

What mac are you running?

  • Yes I have an old 2009 model which I don't currently have on me I'm working away from home. I'm trying to repair the HD again. What do you mean pop up in my desktop? As in show as a start up disk? Is there anything I can do from the bootcamp partition side of things because that's working fine Dec 9, 2014 at 18:01
  1. Attach your thumb-drive and copy all contained files & folders to your external drive, then start Disk Utility.
  2. Copy Install OS X Yosemite to your external drive
  3. Choose your thumb drive in the left pane and repartition it to 1 Partition, click the Options-button, choose GUID Partition Table and OK, then Apply

enter image description here enter image description here

  1. Quit Disk Utility and open Install OS X Yosemite
  2. Install Yosemite to your thumb drive. You may have to click Show all partitions if your thumb-drive isn't visible initially.
  3. After a automated restart configure Yosemite. You will be booted to the thumb drive now.
  4. Start Terminal in Applications/Utiilities/
  5. At the prompt enter df and hit

    The output looks similar to that:

    Filesystem    512-blocks       Used  Available Capacity   iused    ifree %iused  Mounted on  
    /dev/disk1s2   121872696   67379640   53981056    56%   8486453  6747632   56%   /
    devfs                387        387          0   100%       670        0  100%   /dev
    /dev/disk0s2   546875000  328125000  217547952    60% 735912806 22434744   60%   /Volumes/SystemInternalDrive
    map -hosts             0          0          0   100%         0        0  100%   /net
    map auto_home          0          0          0   100%         0        0  100%   /home
    /dev/disk2s2  2923093280 1922781536 1002781536    66% 487048844  1269484   66%   /Volumes/ExternalDrive
    /dev/disk2s3   733093280  142781536  593111744    20% 487048844  1269484   20%   /Volumes/SystemExternalDrive
  6. At the prompt enter diskutil list and hit

    The output looks similar to that:

       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:      GUID_partition_scheme                        *400.2 GB   disk0
       1:                        EFI                         209.7 MB   disk0s1
       2:                  Apple_HFS SystemInternalDrive     280.0 GB   disk0s2
       3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
       4:                     MS-DOS WinSystem               120.0 GB   disk0s4
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:      GUID_partition_scheme                        *62.7 GB    disk1
       1:                        EFI EFI                     209.7 MB   disk1s1
       2:                  Apple_HFS SystemUSB               62.4 GB    disk1s2            
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:      GUID_partition_scheme                        *2.0 TB     disk2
       1:                        EFI                        209.7 MB    disk2s1
       2:                  Apple_HFS ExternalDrive           1,5 TB     disk2s2
       3:                  Apple_HFS SystemExternalDrive    500.0 GB    disk2s3    

    where SystemInternalDrive is the name of your internal system partition,
    WinSystem is the name of your internal bootcamp partition,
    SystemUSB is the name of your thumb drive system partition,
    ExternalDrive is the name of your external data partition and
    SystemExternalDrive is the name of your external system partition (if you have one)

    If your output looks really different, particularly if you have a Apple_CoreStorage device stop here. You have to post the output here and i have to adapt my answer

    Please replace all names in the commands below with your original partition names.

  7. Data copying: You need at least 280 GB free space on your external hard disk to copy your Mac partition. You need additional free space there in the size of your Windows partition if you want to copy that also. Before starting the copy open Disk Utility and unmount the partition SystemInternalDrive and possibly WinSystem then quit Disk Utility.

    Now enter in Terminal.app:

      sudo dd bs=512 if="/dev/rdisk0s2" of="/Volumes/ExternalDrive/RescueMac.dmg" conv=noerror,sync

    hit , enter your password (it will not be visible) and hit again to copy your internal Mac volume to an image file on your external disk though it contains errors. The input file (if) is the Device Indentifier of the corrupted partition found in the diskutil list output above prepended by /dev/r hence /dev/rdisk0s2.
    This will take a good while. If you enter a higher value for bs it should be faster. Using 512 i got 4 MB/s, using 524288 (1024x512) i got about 65 MB/s (but wasn't successful copying my thumb-drive finally). Often a larger integral multiple of 512 is recommended (e.g. 4096 bytes=(8x512)).

    If you also want to copy your boot camp partition that might work:

      sudo dd bs=512 if="/dev/rdisk0s4" of="/Volumes/ExternalDrive/RescueWindows.dmg" conv=noerror,sync
  8. After the process is finished enter exit and hit , quit Terminal, open your external disk with the Finder and open the newly created RescueMac.dmg file. Check if you can open some files or folders.

  9. Start Disk Utility and choose your internal disk in the left pane
  10. Choose Erase and click the Security Option…-button, choose single pass of zeroes like in the picture below and OK then Erase (In the pictures below i have chosen to erase my thumb drive. You shouldn't do that. Since i started from my internal disk – named VMWare Virtual->System – i wasn't able to demonstrate the erasure with that one because it's the start volume and everything is greyed out) enter image description here enter image description here The zeroing will map out bad blocks.
  11. Open Install OS X Yosemite on your external drive and install it to your newly created internal drive. You may have to click Show all partitions if your internal drive isn't visible initially.
  12. After a automated restart configure Yosemite. You will be booted to your internal drive now.
  13. Open RescueMac.dmg on your external drive and copy all needed files to the respective folders in your user folder. Some of your files may be corrupted because they resided on your defective hard disk and got zeroed out in the earlier executed dd task
  14. Get a new internal hard disk as soon as possible and replace your probably corrupted old one like octosquidopus mentioned in his answer
  • Thanks so much for this it worked a treat. I was just about it take it to an apple store before you posted this! You saved me time and money. Will be purchasing a new internal HD ASAP. Once my new internal HD is up and running will it be safe to change my external HD back to fat32 format? Dec 11, 2014 at 8:21
  • @LaurenRoss What's the purpose of the external disk?
    – klanomath
    Dec 11, 2014 at 12:38
  • Kudos for this amazing blog post. Well done @klanomath
    – bmike
    Dec 12, 2014 at 15:18

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