Resize to 350GB using VirtualBox 5.18:
VBoxManage modifyhd "/home/myhome/VirtualBox VMs/arc/arc.vdi" --resize 350000
Full path to virtual disk (e.g., arc.vdi) is important. Without the full path, the following error occurs:
VBoxManage: error: Cannot register the hard disk '/home/myhome/VirtualBox VMs/arc/./arc.vdi' {54199b9e-0a91-4d84-a7d0-fe2b47ed8f47} because a hard disk '/home/myhome/VirtualBox VMs/arc/arc.vdi' with UUID {54199b9e-0a91-4d84-a7d0-fe2b47ed8f47} already exists
VBoxManage: error: Details: code NS_ERROR_INVALID_ARG (0x80070057), component VirtualBoxWrap, interface IVirtualBox, callee nsISupports
VBoxManage: error: Context: "OpenMedium(Bstr(pszFilenameOrUuid).raw(), enmDevType, enmAccessMode, fForceNewUuidOnOpen, pMedium.asOutParam())" at line 179 of file
