1. Error: file '/grub/i386-pc/boot.mod' not found

error: file '/grub/i386-pc/boot.mod' not found.
Entering rescue mode...
grub rescue>
ls
(hd0) (hd0,msdos5) (hd0,msdos1) (hd1) (hd1,msdos5) (hd1,msdos1) (md/1) (md/0)
set
cmdpath=(hd0)
prefix=(mduuid/f107e0bd31c06566333fe834f63d83da)grub
root=mduuid/f107e0bd31c06566333fe834f63d83da
set prefix=(md/0)/grub
set prefix=(md/1)/grub
insmod normal                   --> free magic is broken at 0x6ff87a10: 0x28002
                                --> Aborted. Press any key to exit.
set prefix=(hd0,msdos1)/grub
set prefix=(hd0)/grub
set root=(hd0)

2. Remove extended ACL attributes

# List all files with extended ACL attributes.
ls -alR . | grep '+ '

# Remove extended ACL attribute.
setfacl -bn <file>

# Remove all extended ACL attributes.
setfacl -bnR <dir>