I encountered a significant issue while installing Debian using the debian-installer. When installing Debian on a USB drive intended to be a fully portable OS (with its own bootloader), the installer silently installed or updated the GRUB bootloader on my laptop’s internal EFI partition, even though the target root filesystem and EFI partition were on the USB drive.
This behavior causes the internal system to become unbootable unless the USB stick is plugged in, as the system firmware is directed to the USB's GRUB configuration. If the USB is removed, the system fails to boot with the error: “No bootable device found.”
Steps to reproduce:
1. Install Debian normally on an internal disk (e.g., /dev/sda).
2. Later, install Debian again, targeting a USB stick (e.g., /dev/sdb), intending for the USB to be fully independent.
3. During the installation, the installer does not prompt clearly for GRUB target.
4. After install, the laptop's GRUB was modified and now relies on the USB.
5. Boot fails when the USB is not plugged in.
Expected behavior:
- The installer should default to installing GRUB to the EFI partition of the selected target disk, or at the very least, it should prompt clearly for the GRUB installation target (especially in multi-disk setups).
- It should not modify the bootloader on unrelated disks (such as the internal EFI when the user is targeting a USB install).
Actual behavior:
- GRUB was written to the internal EFI, and the GRUB configuration points to the USB root filesystem.
- Internal system became unbootable without USB inserted.
- There was no clear warning or choice to avoid this behavior during installation.
System details:
- Debian version: Debian GNU/Linux 12 (bookworm)
- kernal: Linux debian 6.1.0-35-amd64 Debian 6.1.137-1 x86_64
- USB drive: 128GB Sandisk
- System: UEFI-enabled laptop, legacy-enabled
This issue lead to boot failure, data loss, and a confusion user experience.
Thanks for maintaining Debian.
Best regards,
Deadlooks