Find your drive that’s supposed to boot with
mount
Or
parted -l
Or
fdisk /dev/sda
And type p to list the partitions, look for type 83.
(If you’ve got Fedora you might have to use the commands „vgs” and „lvs” and if you’ve got mdraid you might have to „cat /proc/mdstat” or mdadm -A –scan or insmod raid1 or insmod raid5 and then mdadm -A –scan) and you will use /dev/md0 or /dev/mapper/my-vg instead of /dev/sda
then try mount it
mkdir /mnt
mount /dev/sda1 /mnt
cd /mnt
ls -l
Is this your drive? Cool!
grub-install --recheck --root-directory=/mnt /dev/sda
(Or whichever /dev drive your root is, with it’s mounted path)
grub-install --recheck --root-directory=/mnt /dev/sda --force
(Force it if it doesn’t like your partitions.)
Now it should boot into grub, and you can use the grub commands to boot up, after rebooting and selecting the right boot drive from the BIOS Setup, or by pressing ESC or F12 depending on your BIOS and whether you are quick enough, then at the Grub prompt – you can use tab completion to find it if it’s not (hd0,1) but (hd1,3) or something else instead, but beware, tab completion sometimes hangs for a few seconds if grub can’t read the drive.
insmod linux
ls
root=(hd0,1)
linux /boot/vmlinuz root=/dev/sda1
initrd /boot/initrd
boot
Or, hopefully you’ve still got an intact grub.cfg file…
ls
ls (hd0,1)/
ls (hd0,1)/boot
configfile (hd0,1)/boot/grub.cfg
or maybe this will work:
grub-mkconfig -o /mnt/boot/grub/grub.cfg
Your paths may differ of course, so just play with these commands until you can see what’s where and what’s going on.
It might be a sign of imminent hard drive failure at worst, or at best maybe just a partition flag or boot file that got overwritten accidentally.
Źródło: Link