Originally Posted by Mi82
@ BW-Userx: I have not tried "cracking the case" of my external HD because I have no experience with that. Is that reversible if it doesn't work? :-o
I'd have to take a look at it. but if it has screws to take it apart then logic states they had to put it together the same way you have to take it apart only the reverse operation. That is if in fact it is just an actual internal HDD that they are using within a case. Otherwise I'd not mess with it if it does not have screws to take it apart. if it is snapped together that'd be one of them be very careful on how you unsnap it you may end up with a duct tape special.
but if screws are holding the case together then it shouldn't hurt to take it apart to get a look at what is inside of it. but if it is a WD External HDD or something like that then they are not made to boot from. as far as I know, and I have already tried that too. didn't work. because they are not made to be used as a bootable hdd. Just storage only. if it is glued together I'd not mess with it. but all hope is not lost yet.
I think perhaps it is a BIOS problem, I had a HP Elitebook 2730p, the BIOS has every port on the laptop listed in the options to boot off of. but none of them actually worked far enough to install off of a USB or SD Card. It's lose the mount when ever the Install jumped to the actual install mode.
just for piece of mind, I'd google around to see if you can find a BIOS update, but be very carful that if you do find one, that it is actually for that laptop/pc BIOS.
take the name of it then use that to google it searching to for anything to substantiate that it is in fact for your BIOS. Get all of your numbers off your laptop, model, make, chip set, using the model search for the specs on it looking for the chip set and possible the actual bios make model numbers anything to further identify it.
Because as you stated you installed it again on that drive without anything else connected then installed grub Hopefully to the MBR. but it is telling you that it is /dev/sda1
you could too try this, put your working Linux Hdd back into your Laptop, then hook up your external HDD get your kernel for 8 then install it along with the necessary files in to the boot directory. this way you know they are there because you put them there. then try supergrub2 to find your kernel on that external hdd to boot it.
or another way to try is -
if you can see your external HDD in a file manager with your internal HDD in your Linux OS that is actually booting up, then Manually install it using that OS instead. this works I know I've done it.
sudo blkid # to get the mount points
grub-install /dev/sdb # to tell it where to install it, it will install on the MBR external
this way you know grub is installed, if not you'll see the errors if any you get when trying to install it on the external HDD from your internal HDD. this too will help you see what the problem maybe.
after grub is installed and updated you'll be using your external HDD to boot off of on both systems, (this is only temporary, until you re-install grub on to your internal HDD, just over write it when you do, it will not hurt anything, then update grub before rebooting or turning off your system to complete the process).
now try booting it, your external HDD will be the first on the grub list to boot off of if in fact it took.
Lilo boot loader can be your next try. Debian LiLo Bootloader
that should give you enough to try for now.