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TOPIC: Volume Rebuild Disk Will Not Unmount

Volume Rebuild Disk Will Not Unmount 22 Apr 2012 21:20 #2299

I have tried several time to rebuild a volume directory. Each time the disk will not unmount to replace the directory. I am running Techtools 6 (latest update) on a partition on a separate physical drive from the one being rebuilt. The last time I went so far as to:

1) Boot in safe mode
2) Dismount all disks including the disk to be rebuilt before running any applications
3) Select the target disk when it is not mounted. I confirmed this visually and it remained unmounted during the initial phases of the rebuild.

I still get the error message that the directory could not be replaced because the volume could not be unmounted.
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Re: Volume Rebuild Disk Will Not Unmount 22 Apr 2012 22:55 #2300

Thanks for your clear and detailed report. I have not encountered this issue before, in which it appears that a volume is already unmounted, and TechTool Pro claims that it cannot be unmounted.

Please use the Console application, located in /Applications/Utilities, to check the All Messages log for any relevant errors that arose during the attempt to rebuild the disk directory.

In case your copy of TechTool Pro is not properly installed, please reinstall the program and repair permissions, using either TechTool Pro or Disk Utility (the results are identical).

In case something in the operating system has become corrupted in RAM, perform a proper shutdown, wait a few minutes for the contents of RAM to be lost, and then reboot.

I have seen cases in which the system software tools related to volumes were corrupted in RAM so badly that they misreported the volume format of a volume.

For future reference, when a volume will not unmount, is it almost always because it has open files on it. Here are detailed instructions for using the lsof command to identify the open files and the processes that have them open:

In order to examine a volume, the Volume Structures test must be able to unmount it.

The most common reason why a volume cannot be unmounted is that it contains open files. We have instructions for using the lsof command to locate the open files.

Here is the text from that page:

If you boot your Macintosh from one volume and cannot unmount another volume, it is because the other volume has open files on it. You can use the "lsof" command to find the open files on a volume that does not unmount or eject. To do this, open Terminal (typically located in /Applications/Utilities) and type:

sudo lsof | grep

Leave a space after the "p" in "grep". Then drag the icon of the volume on which you want to locate the open files to the Terminal window. The pathname for the volume is pasted into the window for you. Press the "return" key. Then, at the prompt, enter your administrator password and press "return".

It may be possible, given the names of the open files that appear in the list, to determine what process has opened them. Finding unexpected open files is frequently a problem with cloned volumes.


Each line of the output of the lsof command refers to one open file. The name of the process that has the file open is at the start of the line, and the complete pathname of the file is at the end.

Here is part of an earlier thread on this topic. The output of the lsof command in the following example consists of these three lines:

coreservi 68 root 10u VREG 14,32 5632 54 /Volumes/Maxtor_BU09/Desktop DB
coreservi 68 root 11u VREG 14,32 38082 55 /Volumes/Maxtor_BU09/Desktop DF
RetroRun 26448 root 25u VREG 14,32 214780244 11347 /Volumes/Maxtor_BU09/Main Backup/Maxtor_BU09.cat

You can ignore any references to DesktopDB and DesktopDF; the operating system can close them.

In the example above, the process named RetroRun shown on the last line (a process used by the Retrospect backup program) has a file named Maxtor_BU09.cat open on the volume Maxtor_BU09. The file is in a folder named Main Backup. The user quit Retrospect (either in the Finder or by using Activity Monitor, located in /Applications/Utilities) and the volume was then able to be unmounted.

Spotlight indexing can cause files to be open:

Spotlight consists of two processes, according to Bombich Forums moderator Andreas:

mdimport user process

mds root process
MicroMat Inc
Makers of TechTool
Last Edit: 08 Aug 2014 17:35 by micromattech3. Reason: Fixed broken link
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Re: Volume Rebuild Disk Will Not Unmount 17 Nov 2012 12:57 #3252

This worked for me, I killed the MDS and the Finder processes, and was able to
rebuild the volume's directory. Thanks!
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Re: Volume Rebuild Disk Will Not Unmount 17 Nov 2012 21:43 #3253

You are welcome, and thanks for your report. It is unusual for the Finder to be a problem, but I have had that happen myself.
MicroMat Inc
Makers of TechTool
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