Don’t panic, because everything is probably all right, and it it’s not, panicking will make it worse, Emily Barr.
“I like the cover," he said. “Don’t Panic. It’s the first helpful or intelligible thing anybody’s said to me all day,” Douglas Adams.
If your computer won't boot, do not panic, at least not yet. Sometimes, battery or power issues, Fast Boot, or an USB device can cause boot problems. Make sure to check your battery, cables, connections, and monitor (is the monitor plugged in?), the power switch on the back is flipped on, plug your computer into a wall socket if it isn’t already, and unplug your USB devices.
Enter your BIOS, and check that your Boot Order is set to the correct hard drive, your RAM is recognized, your CPU is not overheating, and maybe turn off the Fast Boot feature.
bootrec /fixmbr # It restores the Master Boot Record and resolves MBR corruption issues. bootrec /fixboot # It writes a new boot sector that's compatible with Windows to the system partition. bootrec /rebuildbcd # Use this option when you must completely rebuild the BCD.
Boot Repair is a “single click” free and safe tool to recover access to your operating systems (Windows XP, 10/11, Debian, Arch, etc.) and, more generally, repair frequent boot issues you may encounter in Ubuntu when you can’t boot it.
Boot your computer from a CD/DVD or a USB drive with a Ubuntu .iso file installed. Press the Try Ubuntu button, and open a terminal.
Type and run the following commands to add a new repository, install boot-repair, and launch it:
sudo add-apt-repository ppa:yannubuntu/boot-repair sudo apt update sudo apt install -y boot-repair boot-repair
The app will automatically scan your system, then smash the Recommended repair button to repair your GRUB2.
To reinstall Grub, you’ll need the Arch ISO, burn the ISO to a CD/DVD or USB flash drive with Ventoy, balenaEtcher, etc., and boot from it.
loadkeys la-latin1 # Spanish keyboard layout ls /sys/firmware/efi/efivars # Check if UEFI is enabled. sgdisk -p /dev/sda # Print the partition table
mount /dev/sda2 /mnt # It mounts the root partition mount /dev/sda1 /mnt/boot/efi # It mounts the UEFI boot partition arch-chroot /mnt # Enter or switch to the broken Arch system. pacman -S grub efibootmgr os-prober grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=grub # Reinstall grub: --efi-directory=/boot/efi specifies where the EFI System is mounted. --bootloader-id=GRUB is the bootloader identifier. --target=x86_64-efi installs GRUB for x86_64 systems. grub-mkconfig -o /boot/grub/grub.cfg # After the installation, the configuration file /boot/grub/grub.cfg needs to be generated by grub-mkconfig. exit # Exit the Arch System umount -R /mnt # Unmount the boot and root partitions reboot
A good article can be found in AddictiveTips, How to re-install Grub on Arch Linux.