ok this, from fedora documentation, is exactly what i'm trying to do

"If you selected Continue to mount your partitions automatically and they were mounted successfully, you are in single-user mode.
Even if your file system is mounted, the default root partition while in rescue mode is a temporary root partition, not the root partition of the file system used during normal user mode (runlevel 3 or 5). If you selected to mount your file system and it mounted successfully, you can change the root partition of the rescue mode environment to the root partition of your file system by executing the following command:"

chroot /mnt/sysimage
but unfortunately when i try to run this command i get

chroot: failed to run command '/bin/sh': no such file or directory
now do i have a way that i can repair grub on my system?