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WinPE is missing C drive

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10 replies to this topic

#1
ragsboss

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We are seeing a strange issue. When we boot a vm into winpe, we are seeing the C drive is missing. I went through whatever logs are available and did a lot of research on internet and found no clues.

When we do diskpart, and run 'list volume' we do see the volume listed and it does have the expected disk and that disk has expected partitions. The only issue is the listed volume has no assigned drive letter. In fact when we explicitly assign the letter the C drive does come up with all expected content - so I'm not sure this is to do with drivers or anything.

Does anyone have any clue or know how we can diagnose this further? I'm at real loss here and would really appreciate any leads whatsoever.

Thanks Rags


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#2
allen2

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I look like that your winpe (whatever its version) doesn't contain the mass storage driver for the virtual controller of your VM.
Depending what you're trying to do, you'd need to add the virtual controller driver to your winpe or change your virtual controller type in your VM.

#3
jaclaz

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I look like that your winpe (whatever its version) doesn't contain the mass storage driver for the virtual controller of your VM.
Depending what you're trying to do, you'd need to add the virtual controller driver to your winpe or change your virtual controller type in your VM.


owww :wacko: , come on :).
So, the disk is visible and as soon as a letter is manually assigned to the volume on it, by sheer magic the missing mass storage controller materializes itself from thin air? :w00t:

@ragsboss
WHO are the "we"? <-this is just curiosity
WHICH PE is it? <- I mean is it a PE 3.x i.e. made form windows 7 or another earlier version?
WHICH VM is it? <- Some detail might help
HOW exactly was the PE built? <-WAIK or some builder, if the latter which one?
From WHICH device is the PE booted? <-like cirtual CD/iso, seconf hard disk like device, etc.

A possible workaround, NOT a solution, could be to autoexecute a program like the ones discussed here:
http://reboot.pro/10169/

If i were you I would check the PE Registry, namely checking first thing the Mounteddevices / Dosdevices and the Nodrives key, see:
http://diddy.boot-la...nteddevices.htm
http://www.wisdombay...drive/index.php

What is the output of MOUNTVOL?
And the one from dd --list (see the linked thread on reboot.pro)?

jaclaz

Edited by jaclaz, 13 July 2012 - 02:27 AM.


#4
Tripredacus

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I look like that your winpe (whatever its version) doesn't contain the mass storage driver for the virtual controller of your VM.


If the mass storage driver is not installed, Diskpart can't see anything. If you do a LIST DISK, it will return "No fixed disks" message.
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#5
ragsboss

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It's winpe version 2.1. Output of mountvol and registry is in the attachment. The vm is on VMware ESXi 5.

We have a custom build process to customize few aspects of winpe iso file like startnet.cmd. I just noted that call to wpeinit.exe was missing from our startnet.cmd but we ran it after-the-fact but that didn't seem to help. We'll probably try building a new iso with the call to wpeinit.exe... I'll keep you updated.

I'm sorry about the late reply. I didn't get any notifications of this and the problem didn't seem to happen for a long time but recurred again today. Whenever it happens the vm is cloned from a specific source, but we are unable to find any different in vm configuration between this special source vm and other working vm sources...Attached File  winpe_data.png   104KB   9 downloads

#6
ragsboss

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Few more details. Addition of wpeinit.exe call didn't help. However we noticed one interesting thing. The winpe boot happens as part of clone vm high-level scenario. There are some specific source vms that get into this state somehow, such that winpe booting any vm cloned from them will result in missing C drive. We don't know the recipe to create such a buggy source vm - randomly some source vms start exhibiting this weird behavior. Additionally what we found is if the buggy source vm is powered off when clone is invoked, we do NOT see this issue. But when the buggy source vm is powered ON we see this issue.

I'm at a loss on how to find the root cause for this. Does anyone know exactly what process is responsible for assigning drive letters to volumes? Maybe we can find a way to instrument relevant parts of boot logic, if possible to know more about this...

Any help is appreciated.

#7
jaclaz

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We don't know the recipe to create such a buggy source vm - randomly some source vms start exhibiting this weird behavior. Additionally what we found is if the buggy source vm is powered off when clone is invoked, we do NOT see this issue. But when the buggy source vm is powered ON we see this issue.

It is really "strange".
Stiil there must be *something* (very likely in the Registry) differing.
Can you try doing two "clones", one with the VM running and one with the VM shut down and then compare the two registries?

What you report seems like implying that when you make the clone on the powered on VM *something* is seen by the whatever is used to "clone" as *somehow* "busy" or "not accessible" and this "flag" (or whatever) is "transported" to the clone.

(I know that the above is VERY "vague" :blushing: , it is just to convey the "general idea")

Have you tried running "blindly" either mountstorage PE or showdrive in one of the affected clones to see of the issue is solved?

Could it be that somehow the disk gets "offline" (but this should not be possible in a PE 2.1) if I recall correctly:
http://reboot.pro/8200/
http://reboot.pro/82...__25#entry73620

Another possibility is that - still somehow - the thingy gets the NoAutoMount key set:
http://www.911cd.net...showtopic=24551
however the related keys should be the ones mentioned:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MountMgr\
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\partmgr\Parameters

jaclaz

#8
ragsboss

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Our QA guy is awesome. We haven't yet found the solution but he uncovered the recipe to consistently create the repro scenario. Whenever the source vm has "VMWare Tools" installed and is on while cloning from it, the cloned vm will have this issue when booted into WinPE.

I can't understand how that can affect the C drive, but it is. http://www.vmware.co...e-tools-cli.pdf has some details about what vmware tools is made up of. It looks like it has a bunch of device drivers, an auto start service or such. I'm suspecting the hypervisor does some things differently on powering on a vm with vmware tools vs. without vmware tools. This difference is perhaps causing the issue. When we boot the cloned vm using winpe, the vmware tools are obviously not present in winpe but hypervisor blindly thinks vmware tools ought to be present whenever the vm is turned on.

Does this give any concrete clue to someone?

We are using LSI Logic Parallel SCSI adapter for the vm which means the vmware tools' scsi driver shouldn't be used - not sure this is relevant...

#9
ragsboss

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All the credit to our QA guy (Dan) - we found the root cause for this!

Even natively in vmware, we cannot successfully clone a powered on win2008R2 VM with guest tools installed.

Dan found this link which describes the exact problem we hit when cloning natively, which also somehow seems to affect us in winpe boots where the OS volume is missing it's drive letter:

http://kb.vmware.com...ernalId=2004505

We tried the workaround suggested in this link, which is basically this:

To workaround this issue on previous versions of ESX/ESXi 4.1 and ESXi 5.0:
Power down the source virtual machine.
Backup the .vmx file of the source virtual machine.
Change the value of the disk.EnableUUID parameter to False. For more information, see Tips for editing a .vmx file (1714).
Save the changes made to the .vmx file.
Clone the virtual machine again.

After doing this, the problem is gone!

VMware fixed this problem in esx5 update1: https://www.vmware.c...#resolvedissues

In there you can see this is resolved:

Customization of a virtual machine hot clone running Windows 2008 R2 guest operating system fails and the clone reboots continuously
The customization of the hot clone of a Windows 2008 R2 guest operating system fails with the auto check not found error message, and the virtual machine reboots continuously.

This issue is resolved in this release.

I'd like to take this opportunity to sincerely thank all those who replied - in the process we learned some new stuff and discovered this great forum with good folks in it!

#10
jaclaz

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Thanks for coming back and detailing the solution (or workaround) to the issue :yes: .
As a matter of fact, you might have documented something that could be turned to an advantage :w00t: in a few "narrow" fields:
http://winfe.wordpress.com/
:thumbup

jaclaz

#11
dadofthemooch

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All the credit to our QA guy (Dan) - we found the root cause for this!

Even natively in vmware, we cannot successfully clone a powered on win2008R2 VM with guest tools installed.

Dan found this link which describes the exact problem we hit when cloning natively, which also somehow seems to affect us in winpe boots where the OS volume is missing it's drive letter:

http://kb.vmware.com...ernalId=2004505

We tried the workaround suggested in this link, which is basically this:

To workaround this issue on previous versions of ESX/ESXi 4.1 and ESXi 5.0:
Power down the source virtual machine.
Backup the .vmx file of the source virtual machine.
Change the value of the disk.EnableUUID parameter to False. For more information, see Tips for editing a .vmx file (1714).
Save the changes made to the .vmx file.
Clone the virtual machine again.

After doing this, the problem is gone!

VMware fixed this problem in esx5 update1: https://www.vmware.c...#resolvedissues

In there you can see this is resolved:

Customization of a virtual machine hot clone running Windows 2008 R2 guest operating system fails and the clone reboots continuously
The customization of the hot clone of a Windows 2008 R2 guest operating system fails with the auto check not found error message, and the virtual machine reboots continuously.

This issue is resolved in this release.

I'd like to take this opportunity to sincerely thank all those who replied - in the process we learned some new stuff and discovered this great forum with good folks in it!



Thanks Rags! Just came across this old post (don't ask why!)




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