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I'm trying to format a hard drive using Ubuntu 11.10. Every time that I attempt to format it from the Disk Utility, I get the error saying the device is busy, and under details it says:

/dev/sda1 is mounted

Then when I try to unmount it from the disk utility, it shows that the operation has failed and says:

Error unmounting: umount exited with exit code 1: helper failed with:
umount: only root can unmount UUID=70D6-1701 from /boot/efi
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2 Answers 2

Are you sure /dev/sda1 is not the boot partition? You cannot unmount the partition where the system you are running is.

It would be like the coyote cutting a circle around himself with a handsaw.

Instead, boot from a [live-cd] or [usb created with the startup disk utility], and try from there.

but seriously, /dev/sda1 is usually the system partition. If you want to get rid of that you may just try to install something else on top of it.

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I'm not sure why you got that error, but you are lucky you did. The efi partition is what the system uses to boot. Formtting it would leave you with an unbootable system.

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