I am attempting to dismount an external USB drive using powershell and I cannot successfully do this. The following script is what I use:

#get the Win32Volume object representing the volume I wish to eject 

$drive = Get-WmiObject Win32_Volume -filter "DriveLetter = 'F:'"

#call dismount on that object there by ejecting drive

$drive.Dismount($Force , $Permanent)

I then check my computer to check if drive is unmounted but it is not.

The Boolean parameters $force and $permanent have been tried with different permutations to no avail. The exit code returned by the dismount command changes when the params are toggled.

(0,0) = exit code 0

(0,1) = exit code 2

(1,0) = exit code 0

(1,1) = exit code 2

The documentation for exit code 2 indicates that there are existing mount points as a reason why it cannot dismount. Although I am trying to dismount the only mount point that exists so I am unsure what this exit code is trying to tell me.

Having already trawled the web for people experiencing similar problems I have only found one additional command to try and that is the following:

# executed after the .Dismount() command


This additional command does not help.

I am running out of things to try, so any assistance anyone can give me would be greatly appreciated.

  • You probably don't want to dismount a usb drive. You'll have to reassign the drive letter in disk management later. – js2010 Sep 12 '18 at 14:39

A clean solution that doesn't leave any half baked open references like the sample from pk does is:

  $driveEject = New-Object -comObject Shell.Application

Retrieved from http://sushihangover.blogspot.nl/2012/02/powershell-eject-local-or-remote.html

  • My previously posted solution was indeed correct. I'm a bit uncertain as to how I ever offered it up! Please use this method. – pk. Mar 6 '14 at 21:54
  • 1
    Note that this can be made run as a single line from the Run dialog: powershell (New-Object -comObject Shell.Application).Namespace(17).ParseName(\"E:\").InvokeVerb(\"Eject\") – Deebster May 7 '17 at 13:57
  • That one-liner works but without the backslashes. – js2010 Sep 12 '18 at 14:42
  • Unfortuntatly, that does not work here. I also don't get any error message or any error message. $? is True after invoking the second line. Is there anything I can do? – René Nyffenegger Sep 22 '19 at 21:49

I cannot do a great job answering from the PowerShell end, by you might want to look at how mountvol operates. There are different degrees of dismount.

Mountvol or Mountvol /?

Displays the name, globally unique identifier (GUID), and location of the volume.

Mountvol [drive:]path VolumeName

Creates a new volume mount point. Specify either a drive letter root directory or an existing empty NTFS directory as the source of the mount point and a volume name as the target.

Mountvol [drive:]path /D

Deletes an existing volume mount point.

Mountvol [drive:]path /L

Lists a volume name for a given volume mount point.

I tried doing something similar to what you required in VBScript to reorder devices on old desktops where drive mounts for older hardware that was too tedious to remove (read Flash drive) was interfering with shortcuts on a custom GUI where I could only explicit mention mountpoints (D:, E:, F:) with a particular purpose. This became superbly frustrating, and you have to unmount and remount things using mountvol inputs and outputs to verify it went well and proceed with changes. I hope you have better luck than me.

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