Windows HDDs not found after reboot

Troubleshooting
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1

CMK version: 2.0.0p31 (CRE)
OS version: Microsoft Windows Server 2019 on VMware ESXi 7

Error message: [Filesystem E:/] Item not found in monitoring data

Hi everyone,

I monitor Windows Server systems and after a machine reboot all the additional hard drives are not found in the agent output. I have to manually log in once to the server, then the disks are immendiately picked up by the agent. The disks are before this logon accessible to Windows and work normally. Just the Check_MK agent refuses to see them.

2

Maybe check how the checkmk service is run. As you describe it, it sounds like it starts running as the logged in user instead of the local system.

3

Are these actual local drives or shares like SMB/iSCSI or dependent on any external storage?
Is it only the first time the agent runs that they are not available? or never?

4

The Check_MK service is started in ‘Automatic’ mode and logging in as Local System. This is the default as the installer installed it on every Windows Server I have.
All drives are actual local drives directly connected to the machine.
All the local drives except C: are never picked up by the agent as long as there was nobody logged in to the server since it’s last reboot. All other services are picked up normally. So the service runs directly after a reboot. Just the extra drives are ignored.

I can see the agent properly running in it’s logfile. But concerning the (in the example machine) E: drive, there are error messages in the log:

2023-01-06 10:08:33.098 [srv 2852] [Warn ] Information for volume 'E:\' is not available [2150694912]
2023-01-06 10:08:33.099 [srv 2852] [Warn ] GetDiskFreeSpaceExA for volume 'E:\' is failed with error [2150694912]
2023-01-06 10:08:33.100 [srv 2852] [Warn ] Failed FindFirstVolumeMountPointA at volume 'E:\', error is [2150694912]

Those exact same 3 lines repeat on every agent run.

As far as I can find out it’s because the drives are Bitlocker encrypted with automatic unlock but the drives aren’t actually unlocked until a user logs in. This just seems to be a Windows bug.

5

This is indeed a Windows bug. On a VMware virtual machine Windows thinks everything is removable. And Windows doesn’t execute BitLocker automatic unlock before the first user logon.

Workaround to “fix” the problem:

  1. Shut down the Windows VM completely.
  2. Add the parameter devices.hotplug = “FALSE” to the VM parameters.
  3. Start the VM.
  4. Disable BitLocker automatic unlock.
  5. Enable BitLocker automatic unlock.
  6. Reboot the VM.

Now the drives are unlocked actually automatically. But now it is impossible to change VM hardware (like hot-add RAM) as long as the VM is running.

6

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