Originally Posted by descendant_command
The mint15 on the external disk is not running, so any users/passwords from that are irrelevant to this process.
You need root priveleges on your live system to perform the commands, either by logging in as root with 'su' or (presumably) by using sudo to prefix the individual commands (not sure how this is dealt with in mint-live, but it should be documented on their site).
Ty I ran each command from the tutorial and am going to try to reboot now. will update this post after testing.
STILL got same "read error" upon booting to external so had to get back on my thumb drive.
what i did
sudo su -l
mount /dev/sdc1 /mnt/
mount -t proc none /mnt/proc
mount -o bind /dev /mnt/dev
mount -t sysfs sys /mnt/sys
chroot /mnt/ /bin/bash
/usr/sbin/grub-install --recheck --no-floppy /dev/sdc
sync & reboot
I assume I did that correctly changing from sda to what my externals were (sdc sdc1 etc etc)