Hands-on steps to restore GRUB or EFI boot entries using a live system and minimal tools. 16.11.2025 | reading time: 3 min The system drops to grub rescue or a blank screen after an update: he will learn to repair the bootloader manually using a live USB, mounts and a chroot, or quick rescue commands when time is short. Reproduce and repair: a real case Scenario: Windows was reinstalled and overwritten the MBR; Linux no longer boots; boot from a live USB and run the following to reinstall GRUB and regenerate the menu; then reboot to verify: ```sudo mount /dev/sda2 /mnt; sudo mount --bind /dev /mnt/dev; sudo mount --bind /proc /mnt/proc; sudo mount --bind /sys /mnt/sys; sudo chroot /mnt; grub-install /dev/sda; update-grub; exit; sudo umount /mnt/dev /mnt/proc /mnt/sys /mnt``` Example outcome: ```Installing for i386-pc platform. grub-install: warning: this GPT partition label contains no BIOS boot partition; Installation finished. Generating grub.cfg ... Found linux image: /boot/vmlinuz-...``` Fast rescue without chroot If a quick fix is required on BIOS systems, drop to the grub rescue prompt, identify the root with `ls`, set prefix and root, and load normal mode: ```grub rescue> set root=(hd0,msdos2); set prefix=(hd0,msdos2)/boot/grub; insmod normal; normal``` This often boots the system so he can run the full repair from a shell; on EFI systems instead mount the ESP and reinstall the EFI GRUB package or use `efibootmgr` to re-create entries. Key considerations and variations Consider whether the machine uses BIOS or UEFI, whether /boot is a separate partition, and whether Secure Boot is active; use UUIDs with `blkid` to avoid device name pitfalls; when filesystems are damaged, run `fsck` before reinstalling the bootloader; for RAID or LVM root volumes ensure device-mapper is available in the chroot. Other useful recovery tools Graphical helpers can speed the job: `boot-repair` automates many steps, `efibootmgr` manipulates UEFI entries directly, and `testdisk` can recover damaged partition tables that prevent any bootloader from finding the kernel. Next steps and learning path After a successful restore, test cold reboots and document the partition layout and boot commands used; mastering manual repairs builds troubleshooting muscle and prepares him for certification and deeper system work, so explore structured study such as CompTIA Linux+ or LPIC-1 and consider intensive exam preparation at bitsandbytes.academy for focused practice. Join Bits & Bytes Academy First class LINUX exam preparation. boot-process troubleshooting utilities backup filesystem
