To Increase the Size of a VMDK file in Virtual Box (How to increase size of the vmdk HDD with -flat.vmdk )

To Increase the Size of a VMDK file in VirtualBox, if it has a VMDK file with -flat.vmdk 

 Do this Follow below steps,

Remove HDD from Virtual Machine (It won't delete it :) )

Open VirtualBox folder where you install and start CMD (command Prompt) from the same folder

D:\Program Files\Oracle\VirtualBox  (for me I installed it in D Drive )

and then type below command 

1) VBoxManage clonemedium "source.vmdk" "cloned.vdi" --format vdi

Then now new HDD created. :) Now we can resize it ..

2) VBoxManage modifymedium "cloned.vdi" --resize 51200

It will resize disk to 50 GB (50 x 1024)

Now connect it back to VM

Done :)

After that turn on the VM and Go to Disk manager and expand the disk:)

If you want 

VBoxManage clonemedium "cloned.vdi" "resized.vmdk" --format vmdk