/boot/grub/grub.cfg

/boot/efi/boot/grub/grub.cfg

sudo cp /boot/grub/grub.cfg /boot/efi/boot/grub/grub.cfg

#!/bin/bash
# Date: Jun 18, 2022
# Purpose: USB123 copy grub.cfg from boot partition grub.cfg to ESP partition
#      or vice versa if grub.cfg is newer
 
# Only run if the computer is USB123
if [[ ! $HOSTNAME == USB123 ]]; then    # Not on right computer
    echo "This is $HOSTNAME, expected USB123, exiting..."
    exit 1
fi

if [[ "$EUID" -ne 0 ]]
    then echo "This script must run with sudo, exiting..."
    exit 1
fi

BOOTgrubCFG="/boot/grub/grub.cfg"
ESPgrubCFG="/boot/efi/boot/grub/grub.cfg"

if cmp --silent -- "$BOOTgrubCFG" "$ESPgrubCFG"; then
    echo "files contents are identical, exiting..."
    exit 1
fi

if ls /sys/firmware/efi; then   # If TRUE then UEFI Boot
    if [[ "$BOOTgrubCFG" -ot "$ESPgrubCFG" ]]; then    # '-ot` means older than
        cp -f "$BOOTgrubCFG" "$BOOTgrubCFG".old 
        cp -f "$ESPgrubCFG" "$BOOTgrubCFG"
        echo "$BOOTgrubCFG" was old, kept with .old ext
        echo "$BOOTgrubCFG" was replaced with "$ESPgrubCFG". 
    fi
else 
    if [[ "$ESPgrubCFG" -ot "$BOOTgrubCFG" ]]; then
        cp -f "$ESPgrubCFG" "$ESPgrubCFG".old 
        cp -f "$BOOTgrubCFG" "$ESPgrubCFG"
        echo "$ESPgrubCFG" is old, kept with .old ext
        echo "$ESPgrubCFG" was replaced with "$BOOTgrubCFG".        
    fi
fi