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  1. #1
    External Hard Drive.

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    External Hard Drive.
    I have copied all my data off an external hard drive and wish to erase /format contents to use again in future as another back-up. Please talk me through procedure. When I get to Disc Utility Ap on Applications which Format option do I use before pressing ERASE.

  2. #2
    External Hard Drive.
    IWT's Avatar
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    With pleasure.

    Obviously, doing this means total erasure of that External Hard Drive (EHD); so be doubly certain that the data you copied to another source is secure and working.

    With the EHD attached (mounted), open Disk Utility (DU). You will see that Drive listed under External. The top name will be, say, Toshiba XYZ or similar. Indented beneath that will be the name you previously gave that Drive. See screenshot below:

    Screenshot 2019-09-09 at 3.35.22 pm?.png

    In this example, I've chosen WD - WDC etc

    The Indent is TM 2. Click on that. Now click on Erase. This is what you will see:

    Screenshot 2019-09-09 at 3.39.46 pm?.png

    Give it a name. Currently it is TM 2. Call it what you will. Choose the Format as shown. Then click Erase.

    NB Although OS X Extended (Journaled) is shown and recommended for most purposes, you might consider APFS if you are running High Sierra or Mojave and are going to use the Drive exclusively with that computer. Otherwise OS X Extended (Journaled) is the better option and will be compatible with any Mac running more or less any version of macOS X.

    Ian
    Ian

  3. #3
    External Hard Drive.
    krs's Avatar
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    Quote Originally Posted by David1354 View Post
    I have copied all my data off an external hard drive and wish to erase /format contents to use again in future as another back-up. Please talk me through procedure. When I get to Disc Utility Ap on Applications which Format option do I use before pressing ERASE.
    If you are making a back-up using CCC or SuperDuper to get a bootable clone, you don't actually have to erase the external separately - either one of these programs will do that as a first step (and warn you).
    But erasing and formatting first is fine too - I have done back-up clones both ways and don't see any difference in the final result.

    One side comment - if you want to save data on an external, drive or USB flash drive, and if you want people with a Windows PC to be able to read that data, you need to format using MS-DOS or ExFat.
    The Mac can read data on all those file formats - Windows isn't that smart, although I believe there is some Windows app that claims to be able to read Mac-formatted disks...never tried it so I don't know how well that works.

  4. #4
    External Hard Drive.
    RadDave's Avatar
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    Quote Originally Posted by David1354 View Post
    I have copied all my data off an external hard drive and wish to erase /format contents to use again in future as another back-up. Please talk me through procedure. When I get to Disc Utility Ap on Applications which Format option do I use before pressing ERASE.
    Hi David - Ian and Krs have already provided excellent and thorough information to you - just one more point that I did not see mentioned (unless missed - if so, sorry) - if you plan to use that EHD for TM (Time Machine) BUs, then the format needed is 'macOS Extended (Journaled)' (LINK) - now whether Apple in their next macOS release this fall, i.e. Catalina will add APFS as an acceptable TM backup format is unknown to me at least. Good luck. Dave
    If you are helped, increase the reputation of the poster -

  5. #5
    External Hard Drive.

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    Many thanks to you and IWT,krs for your helpful replies.
    Regards David

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