How to Back Up the Linux Bootloader to a USB Drive

Save GRUB settings and boot files to USB; on UEFI systems, also save EFI files and a firmware-entry list. These are recovery references, not a full disk image. If startup code is missing, use Linux rescue media to reinstall GRUB for the actual boot layout.

What a GRUB backup covers

Distributions commonly generate the menu from /etc/default/grub and /etc/grub.d/, with supporting files under /boot/grub or /boot/grub2. Debian documents grub.cfg as generated, so restore settings and regenerate it. BIOS GRUB may use MBR plus embedded sectors; UEFI uses files on a FAT EFI System Partition (ESP) and boot entries in firmware variables.

Back up GRUB to a USB drive

1. Mount the USB and identify the boot mode

Connect a USB drive, open it in the file manager, and note its mount location. Then list disks and check how the current system was booted:

lsblk -o NAME,SIZE,FSTYPE,LABEL,UUID,MOUNTPOINTS
findmnt /
if [ -d /sys/firmware/efi ]; then echo UEFI; else echo BIOS; fi

Use size, filesystem, label, and mount point to distinguish USB from internal disks. Names like /dev/sda can change, and the root partition is not always the BIOS bootloader’s target disk.

On UEFI systems, identify the EFI System Partition (ESP) in the output. It is often FAT32, with a mount point such as /boot/efi, /efi, or /boot. It usually contains an EFI directory.

2. Archive GRUB settings and supporting files

Replace the example USB path with the mount point you found. Keep quotation marks around paths that contain spaces.

USB="/media/$USER/USB_LABEL"
BACKUP="$USB/grub-backup"
sudo mkdir -p "$BACKUP"

paths=(etc/default/grub etc/grub.d)
for p in etc/default/grub.d boot/grub boot/grub2; do
  [ ! -e "/$p" ] || paths+=("$p")
done
sudo tar -C / -czf "$BACKUP/grub-files.tar.gz" "${paths[@]}"

The archive preserves Linux permissions even on USB filesystems that do not. It includes the optional GRUB directories found on this installation.

3. On UEFI, save EFI files and firmware entries

Set ESP to the mount point you identified; this example uses /boot/efi. The archive includes other vendors’ files if they share the EFI directory.

ESP="/boot/efi"
sudo tar -C "$ESP" -czf "$BACKUP/esp-files.tar.gz" EFI
sudo efibootmgr -v | sudo tee "$BACKUP/uefi-boot-entries.txt" >/dev/null

efibootmgr -v prints boot-entry details, not every firmware setting. Skip these commands on BIOS-only systems.

4. Verify the backup and eject the drive

tar -tzf "$BACKUP/grub-files.tar.gz" | head
[ ! -f "$BACKUP/esp-files.tar.gz" ] || tar -tzf "$BACKUP/esp-files.tar.gz" | head
ls -lh "$BACKUP"
sync

Check that the archive names and sizes look plausible, then eject the USB before unplugging it. Keep the backup separate from a live-installer USB that may be erased while creating boot media.

Use the backup after a boot failure

5. Start a live session in the installed system’s boot mode

Boot a Linux live or rescue USB in the same UEFI or legacy BIOS mode, if possible. Identify the root, any separate /boot partition, and the ESP again; device names may differ.

Mount the installed system at a temporary location such as /mnt/target, with separate boot partitions mounted at their matching paths. Follow your distribution’s instructions for the exact partition and chroot commands.

6. Restore settings selectively, then repair GRUB

After mounting the installed root and any separate /boot partition, restore the archive only if it came from this installation and release:

sudo tar -xzf "/path/to/grub-backup/grub-files.tar.gz" -C /mnt/target

Replace the example path with the USB’s actual location. Do not extract the EFI archive over a shared ESP; use the distribution’s reinstall steps to recreate boot files and the firmware entry. Secure Boot may require signed shim and GRUB packages.

In the chroot, regenerate the menu using your distribution’s command and output path. Debian and Ubuntu commonly use update-grub; others document grub-mkconfig or grub2-mkconfig. If startup code is missing, reinstall GRUB for the correct BIOS disk or UEFI partition. Verify the target before grub-install.

Why not restore only the first 512 bytes?

A one-sector copy misses BIOS GRUB’s embedded image or BIOS Boot partition when used. The first sector also contains partition-table data, so restoring an old copy can damage a changed disk. UEFI files and firmware entries are separate. Use this archive as recovery information; keep a tested whole-disk image for full rollback.

Official references

• GNU GRUB Manual: BIOS installation and embedded boot areas
• GNU GRUB Manual: installing GRUB
• Debian Administrator’s Handbook: GRUB configuration and EFI
• Debian Manpages: efibootmgr