How to reformat an encrypted Time Machine drive?

Discussion in 'Mac Basics and Help' started by tuna, Nov 25, 2013.

  1. tuna macrumors 6502

    Apr 11, 2010
    I haven't done anything at all outside of the Apple ecosystem. I have a Time Machine external drive that was encrypted using the included Time Machine encryption options.

    I want to temporarily use this drive for something else (the contents of my computer aren't that important, I am willing to give up my backup history and take a small risk that my computer will crash in the next day or so as I go backupless).

    However, when I went to "Erase" the encrypted drive in Disk Utility and chose the fastest option (which doesn't even overwrite the disk), my computer told me that it was going to take 3 hours (and that was after it had already been going for a half hour, and in fact had never shown any forward progress). Normal erase procedures at the fastest option take a couple minutes. I am also normally able to simply reformat the disk as a new partition and I understand that the old data isn't overwritten, but it takes less than a minute and its all I need. In this case, the options to repartition my encrypted Time Machine drive are greyed out.

    How can I reformat my encrypted Time Machine drive?
  2. mac8867 macrumors 6502

    Apr 5, 2010
    Saint Augustine, FL
    To reformat a drive, your first delete the partition(s), using Disk Utility. Then create a new partition and format.
  3. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    Three things to try.

    Once in Disk Util click in the File menu then click "unlock" and provide the password. I think that will then allow you to erase the partition normally.

    If that won't work, try clicking at the top on the drive brand name itself (like Seagate 1TB) and not on the partition. Then try to erase.

    If that won't work, plug the drive in then enter "diskutil cs list" (without the quotes) in Terminal then post the output of that command here and I can give you a Terminal command to force kill the encrypted partition.

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