Problem solved. It turns out I just needed to run update-brug, without any manual changes, and Grub changed the configuration files under /boot/grub from hd3 (incorrect) to hd2 (correct.) A big relief.
I wonder if there's any way the installer could make this more intuitive, or at least issue a reminder. Alan On 3/14/20, Alan Tu <[email protected]> wrote: > I think I have diagnosed the problem, but I don't know how to fix it yet. > > The configuration files under /boot/grub show that root is found as > hd3,gpt2. I read Grub hd numbers start at 0, so hd3 would be the > fourth hard drive. But when Grub boots successfully this one time, the > USB drive is at /dev/sdc, the third hard drive. > > I could edit the files in /boot, but the comments say don't do that. > And I haven't found a reference to hd3 in the files under /etc. > > Alan > > > On 3/14/20, Alan Tu <[email protected]> wrote: >> Hi, I don't know how to fix this. I used an ISO image burned to one >> USB to install Debian to a second USB. I did this twice, with just one >> difference: >> >> 1) At the end of the install, both USB are connected to the computer. >> When the text installer prompts me, I remove the installation USB, >> then press Enter. The new Debian system boots. >> 2) At the end of the install, both USB are connected to the computer. >> When the text installer prompts me, I remove the installation USB, >> then press Enter. But this time while the BIOS is posting, I remove >> the second USB and let my computer boot into Windows. I then >> completely power off the machine. I then re-attach the second USB with >> the installation. Computer boots to Windows. The second USB doesn't >> boot. >> >> I should add I am blind and cannot see the messages that a potential >> bootloader might output. >> >> I ran this contrived test because the bootable USB drives I installed >> on only booted once. (While trying these scenarios, I'm getting quite >> familiar with all the numeric menu choices in the text installer.) >> >> When the installer boots, it is attached to /dev/sdc. (I have two >> built-in hard drives.) During the install, the target USB drive is at >> /dev/sdd. But when I'm booting the system with only the installation >> target USB attached, that probably is not /dev/sdd at that point. It >> would probably be /dev/sdc, if the kernel knows about such things at >> this point. I'm not sure if this is my problem. >> >> I have read about Grub refering to hard disks by number, like hd0. But >> I just don't know what to do. >> >> I don't want to modify my original Windows boot drive with a >> bootloader. All I want is to boot into Debian when I insert the USB. >> But I'm really stumped. >> >> Alan >> >
