Caution: I would use the second method.
Command Prompt in the VB program folder (I opened as admin. but don't know if necessary.)
Be sure to use the quotation marks
Be sure to use the two (2) dashes before "resize"
After resize success:
You will need to expand the partition with GParted (not done yet so not sure) You can virtual boot into live Gparted and still have the original live disk attached. All done in the virtual machine.
Syntax:
VboxManage.exe modifyhd "C:\Users\User Name\VirtualBox VMs\virtual disk folder \virtual disk name.vdi" --resize 15000
(Your user folder may not be on C:\ so adjust for your situation.)
So.... It didn't work but looked successful in command prompt. GParted run the way I described above shows the drive is still 8GB with no unassigned space. May need to create blank larger disk and copy/clone over then expand in GParted. Let's just forget the whole VboxManage.exe thing.
Not only that but I can no longer attach the vdi on which I ran the resize command.
I'll be back ....