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External hard drive with Catalina

I upgraded to Catalina and since then unable to use my external hard drive...it is not recognized but when i use sierra it all there

Posted on Feb 19, 2020 1:11 PM

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Posted on Feb 19, 2020 1:18 PM

is this an error message or are you suppressing the external drive appearing on the desktop in Finder>Preferences>general


does the drive appear in Disk Utility?

Macintosh HD (whatever you named it}/Applications/Utilities/Disk Utility.app


how is it formatted?


11 replies

Feb 19, 2020 3:39 PM in response to videomanR

videomanR Said:

External hard drive with Catalina: I upgraded to Catalina and since then unable to use my external hard drive...it is not recognized but when i use sierra it all ther

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Using Disk Utility:

1. Using First Aid in Disk Utility:

Run Fist Aid in Disk Utility and see if it shows a corrupted hard drive. Boot into Recovery Mode select drive name along the left and click First Aid along the top. Run it and see what is reported.


2. Mounting the Drive in Disk Utility:

  • Disk Utility in MacOS:

If mounting it in Terminal is of no success, use Disk Utility. Open it using Spotlight Search: Hold down [command + spacebar] and type: Disk Utility. Click on the drive and select Mount along the top.


B. Disk Utility in Recovery Mode:

If that cannot be done, mount this in Recovery Mode. Hold Down [command + r] upon boot. Select Disk Utility, and mount the drive. Click on the drive and select Mount along the top. Reboot the Mac and log in as an administrator, seeing if it is now seen and accessible.

Feb 19, 2020 2:27 PM in response to videomanR

It sounds like the disk is not mounted. In Disk Utility when you select that volume is the "Mount" button active?

If that doesn't work try this:

Launch/Utilities/Terminal and copy & paste this command at the prompt:

diskutil list

Press return.

If it sees the disk, note the number of the disk (far left column) you want to mount.


Then, copy & paste this command:

mount /dev/(number of disk)

Put in the number no parenthesis.

Press Return.


Also might try

mount force /dev/(number of disk)


External hard drive with Catalina

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