I want to use a new hard drive for time machine. I try to restore the old backup into the new disk using disk utility. It fails with the following error :

source volume is read-write and cannot be unmounted, so it can't be block copied

Why ? What can I do ?

1 Answer 1


Problem understood. The disks were actually locked by the failed copy of the backup folder I tried to do between the two disks shortly before.

If it happens to you, just make sure the disks are not locked. In the worse case, reboot.

  • Please mark this as the answer if your issue is resolved. Thank you!
    – bneely
    Commented Mar 15, 2014 at 18:43
  • any chance you could elaborate on this? Ive no idea what any of this means, but reboot didn't help Commented Sep 25, 2016 at 22:34

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