How to force a Hard Drive to unmount for formatting in Mac OS X Disk Utility

Author: Gemsbok Apple Tips and Tricks
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6m 11s Lenght
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Have you ever tried to format a disk in Mac OS X and Disk Utility won't Unmount the Hard Drive for formatting? It can happen for external (USB and Firewire) as well as internal disks. In this video you will learn how to force a disk to unmount when Disk Utility won't do it. You will need a Mac running OS X and this is supported in all versions right up to Mac OS X 10.12 Sierra. Here, we are demonstrating wit Mac OS X 10.10 Yosemite. The commands you will need are: diskutil list diskutil unmountDisk force /Volumes/VOLUMENAME diskutil unmountDisk force /dev/diskN If you have any questions or suggestions for new tutorial videos you would like us to post, please put them in the comments below. If you would like to arrange one-on-one help or remote help, please contact us through our website at: http://www.gemsbok.ca

Comments

Hi could you do a vid explaining what the Mac OS X base system is, and if I want to do a complete reinstall via USB. How to remove the disk (Base system) Thanks
THANK YOU!
when i tried my WD HDD in mac : Volume on disk2s2 failed to mount
If the volume is damaged, try the "readOnly" option ... please help me .. All important files are inside
usefull)))
Thanks for your tutorial. Recommend
It did not work, it said "Unmount failed for /dev/disk1i" . what's next?
Tried the first method, it came back with the error msg "unmount failed for force".
Tried the second method, worked like a charm!
Thanks, great vid!
please my external ..writes always.,,the disk is not readable ...with the option to initialize but doesnt work,eve if i try to..pls helppppppppp!!!!!
I did that but did not work! . It shows my drive low colour mode !
Sir i need your help.. :(

when i try to erase/reformat my drive i get the error message "erase process has failed". When i click details it says..

unmounting disk
wiping volume data to prevent future accidental probing failed.
Operation failed..

i followed the steps outlined in this video twice and still get this same message, any ideas on how to help me please..?
This worked for me to unmount the disk but could not format external hard drive because disk utility was unable to write the last block of device Help Please.
I'm trying this and I used the dev/disk. It seems to be stuck on partitioning when I go back into disk utilities to erase the SSD that I'm trying to format.

Update: I am still having the issue of the Partitioning estimated time increasing.

So this didn't help.
thx worked perfect
Forced unmount of disk2 failed: at least one volume could not be unmounted__ PLS HLP
Hey,
I tried it but it give error msg : unmount failed for force.
Can you help me out? Thanks
Great help video - I'd been struggling to sort this out! Really appreciate the step by step explanation!
how can i use dev/disk plzz ? Gemsbok Apple Tips and Tricks
Hey buddy, can you please help?

Received a new USB thumb drive today, and was copying some files over. Things were taking too long, so I chose to cancel the copying of some of the files.

Now, one of the files are greyed out and the drive is read only!

This has been driving me crazy for hours, and I simply do not know what to do?

A friend of mine tried to get things working on his PC, and told me he'd taken care of it. However, this is not the case as not only is the greyed out item still there but there is now a second partition on the drive which is also read only.

I honestly feel like stamping on this thumb drive, as it's taken my whole day to achieve nothing!

Would you please help?

Thank you ...

PS, I just tried the following but was greeted by "Permission denied":

sudo diskutil unmountdisk force disk1

sudo dd if=/dev/zero of=/dev/disk1 bs=1024 count=1024

... the unmount worked, but the second part (which I'm assuming is a forced format?) was denied.
Thank you so much my friend, you are a life saver.
it said it failed :(