Setting Up CPTC Practice VMs in Proxmox

Virtual machines from prior CPTC competitions can be found at cptc.rit.edu. This post covers how to import those VMs into Proxmox and recover credentials on both Linux and Windows machines.

Importing a VMDK into Proxmox

Based off this YouTube video.

1. Create a Virtual Machine

• Give the VM a name
• On the OS tab, set to “Do not use any media”
• On the Disk tab, configure whatever you want — this disk will be deleted
• Set CPU, memory, and network as normal
• Click Create

2. Remove the Default Disk

1. Detach the drive from the VM
2. Once detached it will appear as an unused disk — remove it
3. The VM should now have no disk attached

3. Import the VMDK

Open the shell on the Proxmox node hosting the VM and download the VMDK file:

wget <url-to-vmdk>

Then import the disk using:

qm importdisk <vmid> <file> <storage>

Example:

qm importdisk 200 example.vmdk tank

Replace tank with your storage pool name if it differs.

The disk will now appear as vm-<vmid>-disk-0 under VM Disks in storage.

4. Mount the Imported Disk

Before mounting, ensure the SCSI Controller is set to VirtIO SCSI.

Double-click the unused disk to mount it:

• Set the bus device to SCSI
• Confirm the correct disk image is selected
• Click Add

To expand the disk, select it and use the Resize Disk option.

5. Set Boot Order

Go to Options → Boot Order, add the new drive, and drag it to the top.

The VM is now ready to start or clone as a template.

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Recovering Credentials on Linux

To reset the root password after importing a Linux VM:

1. Spam Shift during boot when the Ubuntu logo appears
2. Press e to edit GRUB commands
3. On the line beginning with linux, change ro to rw and remove any console= options
4. Append init=/bin/bash to the end of that line
5. Press Ctrl+X to boot — you should drop into a root shell
6. Remount the filesystem as read-write:

   mount -o remount,rw /
   

7. Change the root password:

   passwd
   

8. Reboot:

   reboot -f
   

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Recovering Credentials on Windows

To reset a forgotten administrator password on a Windows VM:

1. Boot from an ISO and open a Command Prompt
2. Navigate to System32:

   cd /d C:\Windows\System32
   

3. Back up Utilman.exe and replace it with cmd.exe:

   copy C:\Windows\System32\Utilman.exe C:\Windows\System32\Utilman.bak
   copy C:\Windows\System32\cmd.exe C:\Windows\System32\Utilman.exe
   

4. Boot the machine normally
5. On the login screen, click Ease of Access — this now opens a command prompt
6. Reset the administrator password:

   net user administrator <password>
   

7. Once logged in, restore Utilman.exe:

   takeown /f Utilman.exe
   icacls Utilman.exe /grant administrators:F
   copy Utilman.bak Utilman.exe