Every so often, it’s necessary to resize the boot drive of an existing virtual machine. The process of resizing the VM’s boot disk from outside the VM is usually pretty straightforward:
1. Shut down the VM
2. Go into the VM’s drive settings
3. Resize it to the desired size
4. Power on the VM.
However, when the VM boots up, the disk space used by the OS won’t have changed.
However, the OS can detect that there is available unallocated disk space that it isn’t using.
Fortunately, this is a correctable condition and the fix can be applied without needing to shut down the VM or boot from another drive. For more details, see below the jump.