welcome to Tips & Tricks gemsbok is an
apple consultant and we help you with
all of Europe with hardware software
needs today we're going to talk about
problem where Disk Utility won't format
a drive because it can't unmount it so
in this case we have a external USB disk
is he right here we've got a plugged in
and we want to reformat it you want to
wipe it out and reformat it usually in
Disk Utility you would select either the
volume partition or the disk itself and
you should be able to erase it so here
if we choose erase to format it will
choose the Mac format and we'll just
leave it being cold untitled we're go to
erase try to erase and we get an error
there's a couple of errors you can get
and this one there saying it couldn't
open device and sometimes you'll get an
error saying it can't unmount the device
for formatting so it's possible now to
force the device to unmount and then we
can format it so we will use the command
line to force the disk to unmount we can
get some information about the disk by
clicking on it and we can see a
description where it's located and so on
and if we click on the partition we get
the name of it where it is and so on but
we can get a little bit more information
out of the terminal so remember to open
the terminal to put in the command line
commands you go into your Applications
folder and then into your utilities
folder and terminal will be sitting in
there so here we can use Disk Utility
commands disk util is the main program
that we're using and we can issue
commands here so we can just say lift so
if we type in a list we get a list of
all the disks that are located on the
Mac so here we can see the Macintosh HD
which is our main startup
and we can see our external drive so
here it's called USB disk USB disk and
we can see what the actual name of the
disk is so in case the drive is really
messed up and it doesn't have a name or
volume and you plug it in but it still
won't under meant to reformat you can
run this command here to find out the
name and location of the disk itself and
I'll show you how to force the unmount
based on that in a minute okay or just
clear this window so we want to unmount
this disk so what we will do since we
know the name of it is we will type in
disk your till and mount disk force and
then we type in volumes and the name of
the volume itself so in this case it's
USB underscore disk let's be honest core
disk your return and it's forced the
volume to be unmounted now we can go
back in here and we should be able to
format it let's go ahead and format it
perfect you've got a newly formatted
disk it's ready for use so what do we do
if we don't know the name of that volume
of the disk so let's say this is messed
up it's not really appearing on our
desktop but we're still getting errors
in Disk Utility when we want to format
the disk well we know from running our
list disk util list that this disk is
actually located here slash dev slash
disk two we can tell that when we do our
list and even if the names not here
you're not 100% sure you can identify it
by the size the fact that it's not this
one because we know that's our startup
drive so by process of an elimination
you can really tell what the disk is and
where it is so in this case well force
it to unmount without knowing the name
so here we use the same command desk
util unmount disk capital D force slash
dev slash disk to enter there we go
and mounting was successful it's
disappeared from the desktop and now
we're ready to format it again if this
video was helpful please give it a
thumbs up and if you have any questions
or comments on new topics that we can
post in new videos please put them down
in the comments below I'll also put the
commands down in the comments below for
your reference and if you have any
further questions or you would like to
set up one-on-one help you can get in
touch with us through our website which
is linked in the description and as
usual please subscribe comment like and
share