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diskutil unmountDisk disk3 > to unmount the EFI partition if it reappears on the Desktop. sudo gpt remove -i 1 disk3 > to delete the partition. diskutil unmountDisk disk3 > to unmount the EFI partition. Secure erase options are available only for some types of storage devices. The commands to use are: diskutil list > to find out the disk on which the EFI partition to be repaired is example: /disk3. Tip: you can experiment with different numbers for the block size by replacing bs16M with larger or smaller numbers to see if it makes. You can also burn to a CD, boot it and try to format your external HD from it. See What is the ‘Mac OS X Base System’ disk image on my 2011 Macbook AIr To get an explanation.
COULD NOT UNMOUNT DISK MAC OS X MAC OS X
(Optional) If available, click Security Options, use the slider to choose how many times to write over the erased data, then click OK. Copy the SD card as a disk image (dmg) Now you should run the following command, replacing 4 with whatever number you identified as your sd card: sudo gdd if/dev/rdisk4 ofsdbackup.dmg statusprogress bs16M. The Mac OS X core system image is not the cause of your problem.
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COULD NOT UNMOUNT DISK MAC OS X PORTABLE
Help Disk Utility Failed to Repair This Disk 'My external drive is a Samsung M2 Portable 3 Media, 500GB.
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If the Scheme pop-up menu isn’t available, make sure you selected the storage device you want to erase - it’s at the top of the hierarchy.Ĭlick the Format pop-up menu, then choose a file system format. Depending on how you went about the work, installing Mac OS X on the new system may give you a message: OS X could not be installed on your computer. Ĭlick the Scheme pop-up menu, then choose GUID Partition Map. In the sidebar, select the storage device you want to erase, then click the Erase button. If you want to erase any other type of storage device: Double-click Disk Utility in the /Applications/Utilities folder. 2.) Connect your USB thumb drive to your Mac, then launch the DiskMaker X application from your Applications folder. Note: If you want to get your Mac ready to trade in, sell or give away, and your computer is a Mac with Apple silicon or an Intel-based Mac with an Apple T2 Security Chip, use Erase Assistant.