Re: GRUB Error 21 after install

[Roby <ElectricalSciences@Adelphia.net>]

wednspecial@verizon.net wrote:

> I installed Debian onto a usb hard drive (sda) using a laptop that already
> had Debian installed.  Now when I try to boot up the laptop, I get the
> following error:
> 
> GRUB Loading stage1.5
> GRUB loading, please wait...
> Error 21
> 
> I know that Error 21 means that GRUB can't find the disk drive.  The
> menu.lst file only refers to the hard drive on the laptop (hda).
> 
> When I use a Knoppix CD to look at the laptop, the Linux partition is
> still on hda2.
> 
> I get this error whether or not the usb drive is attached.
> 
> How do I get the laptop to boot again?

Re-write the mbr on your internal HD like this:

grub> root (hd0,1)
grub> setup (hd0)

Then reboot.