Cant unmount disk mac external hard drive

The reason for this error is the modification of the boot drive, or it is being used by some other process or application. If the internal drive is causing the issue because the OS X Recovery exists as a partition on the physical disk, unable to modify or unmount the internal drive, then the preference must be given to a network drive or an external drive.

Disk Utility can be run from the external drive. The version of the OS X does not matter, by at least must be The one and only requirement are that Disk Utility must reside on the drive.

Easy Fix: Mac: External Drive Not Ejected Properly

Formatting the hard drive or partition scheme will recreate new HFS file structure on the hard drive, which will be free from cryptic errors. This is the most recommended method to repair the error. Any OS X boot drive is needed to complete the task. But, the important point to remember is that the installer or the recovery drive must reside in the drive, separate from the primary boot disk with the installed OS on it. The above steps offer a resolution of the problem. The errors could have been unresolvable without a boot drive.

Therefore, a bootable thumb drive was a good option. For the older Mac OS X like The above error may also be triggered due to first Aid or while formatting a non-boot partition. In this case, a resolution of the problem occurs with the Recovery Partition, which comes with all the newer versions of the Mac OS X. However, this is not applicable for the modification of the boot disk with the help of partitions or formatting.

Then the resolution lies in the previous method. Otherwise, we follow the steps: This will not work with the disk that is throwing the error is the same as the primary boot partition. The solution lies only in using a separate USB drive for fixing the error. Vishal is a data recovery expert Stellar addressing several data loss scenarios on a macOS system. He loves to read autobiographies and his personal favourite is of Steve Jobs.

View More. Please help me recover as the SSD contains important projects and documents. I suggest you to install Stellar Data Recovery Professional for Mac to recover your important documents and to avoid any data loss risk. The software scans your unrecognized SSD and list all the recoverable files. To save the files, you need to register the software. Leverage Stellar Mac Data Recovery and you can recover data from unmounted disk conviniently. Thanks for another informative blog. Where else could I get that kind of info written in such a perfect way? Would you recommend some solution for data recovery?

Yes, we have solution for unmounted data recovery on MacOS. You can watch the tutorial video and then download Stellar Mac Data Recovery to recover your files. Recently i bought it from my friend. Then i upgraded it to Mac OS high sierra successfully. I installed it and tried many times to upgrade to Mac OS high Sierra. But failed to installed. After 5 hours of download, the installation requires the system to restart but the restart is failed. I am very depressed and stuck with the mountain lion.

Can't unmount my External Hard Drive? - Apple Community

Did you try erasing the Apple hard drive via recovery mode? Once in Recovery Mode, you can go to Disk Utility and erase the complete hard drive to a single partitioned drive. Just the solution I was looking for.. This worked for me — easy and no separated USB drives required. Your email address will not be published. Your password is being accepted. There are just no dots or asterisks to indicate so.

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What to do when the problem happens when i am trying to erase the internal hard drive to sell my pac book pro? Try booting into recovery mode holding down Cmd-R during bootup and then erasing it from there. Great tip. This worked great. Took a lot of time to find it but was a flawless solution. Thanks very much. I have been trying off and on for weeks to get rid of this error.

5 Solutions to “Couldn’t Unmount Disk” Error when Using Disk Utility on Mac

I searched high and low and your directions were the easiest to follow and actually worked!! Thank you very very much. When I try to do this I get an errror on the terminal saying Sudo command unknown… Any ideas?


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I would suggest copy and paste. Standard accounts do not have enough privileges to escalate using sudo. I was trying to install tacos sierra on my iMac So now i have two broken internal hard drives. Have an external hard drive, which i used to boot up the iMac with el capitan, but i am still in the process of trying to erase the internal drive. Thank You! Sierra is still beta, right? If the external El Capitan absolutely refuses to unmount the disk, can you try booting into Recovery Mode hold down Cmd-R while booting up and then using Disk Utility there?

Unmounting disk Wiping volume data to prevent future accidental probing failed.


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  • Operation failed…. Based on the output you posted, your disk might have unmounted just fine. It looks as if the failure came from the wiping part. You may find these links helpful: Thanks so much for the quick and easy tip. Worked like a charm for me to reformat an external drive. Is there a way to work around needing a password? You may be able to rectify this issue by booting into single user mode, and then after the fsck scan renaming the home folder back.

    You really have to tackle one problem at a time. First, figure out your password. Invalid Request. I am trying to format a windows pre-formatted hard drive to use on my mac. This may help you: Unmounting disk Operation failed… Unable to write to the last block of the device. I watched the video posted here that says to partition it, but my partition button is greyed out, what can I try next? If it successfully unmounts the volumes, the volumes are unmounted and thus should not show up in Finder.

    Is there a way to restore the data prior to erasing using the steps above? Current error: And what are you trying to do? Get data off the volume before erasing it?

    Great piece of advice! Worked at first attempt, I was running out of hope after trying several solutions from other forums. Thanks for the post. Forced unmount of disk2 failed: Yeah, unfortunately, no idea on that. Honestly, since that appears to be an external drive, I would shut down the computer and then just unplug the drive.

    I have tried all the methods listed in previous comments. I used to have a boot camp windows 7 that was deleted a year ago If that would effect it. I am not using any external drives. After trying for several hours, came across this solution and it worked perfectly, thanks much for posting this! Either way, glad this worked. How do you know which one to choose to unmount? Disk erase failed. Type df -h and hit Enter to see free disk space but this will also show the mounted paths. I also tried it in a different command on the other page you referenced: Why are you trying to unmount Macintosh HD?

    Are you booting from an external drive? The Apple instructions https: Boot into recovery mode hold down Cmd-R while rebooting and then you should be able to unmount and erase Macintosh HD. Hence this series if inquiries. If you really want to erase the entire disk, including the recovery partition, you must boot from an external drive.

    Anyway, it sounds like I should be good to go. Thanks for the help, I really appreciate it. Thank you so much! It took me an hour to find your page and I am glad that I did.