virtualbox.org

C:\Program Files\Oracle\VirtualBox>VBoxManage modifyhd "C:\Users\Regaogetswe Mashile\VirtualBox VMs\Ubuntu_PC\Ubuntu_PC.vdi" --resize 51200
0%...
Progress state: VBOX_E_NOT_SUPPORTED
VBoxManage.exe: error: Failed to resize medium
VBoxManage.exe: error: Resizing to new size 53687091200 is not yet supported for medium 'C:\Users\Regaogetswe Mashile\VirtualBox VMs\Ubuntu_PC\Ubuntu_PC.vdi'
VBoxManage.exe: error: Details: code VBOX_E_NOT_SUPPORTED (0x80bb0009), component MediumWrap, interface IMedium
VBoxManage.exe: error: Context: "enum RTEXITCODE __cdecl handleModifyMedium(struct HandlerArg *)" at line 816 of file VBoxManageDisk.cpp

AFAIK, this is always user error.

The size provided (51200) must be larger than the existing disk - it is an absolute size (in MB), not an increment.

The VDI in question can't be a fixed size disk.

Say which of these two corresponds to your case and we can then offer solutions.

Or I can refer you to my previous answer from two weeks ago: viewtopic.php?f=6&t=104861.

virtualbox.org

Failed to resize medium

Failed to resize medium

Re: Failed to resize medium