GRUB and System - on different disks (on computer with BIOS)?

[Lesha]

Computer with BIOS. I assume, but I'm not sure. I don't want to try it unnecessarily. What will happen to the MBR record on the system disk if I install the system on the SSD, and GRUB on the USB? Will the MBR of the system disk on the SSD remain in the same state as before the installation (without information about the system, only with the disk marking for the system). On the MBR of which disk will the information about the system itself be written?

[Aki]

Hello,

Computer with BIOS. I assume, but I'm not sure.

Who does it know better then you ? You can verify with:

• Package: boot-info-script

What will happen to the MBR record on the system disk if I install the system on the SSD, and GRUB on the USB? Will the MBR of the system disk on the SSD remain in the same state as before the installation (without information about the system, only with the disk marking for the system). On the MBR of which disk will the information about the system itself be written?

It is possible to boot the computer from one disk (i.e. external USB disk) and load the operating system (Debian) from another disk. This is not very practical unless you have special requirements. The way to do it changes depending on the type of boot (legacy vs. UEFI).

There are solutions ready to use; i.e.:

• https://www.supergrubdisk.org/super-grub2-disk/

Another different solution is:

• Ventoy - A New Bootable USB Solution

Hope this helps.

[Lesha]

Hello,

Computer with BIOS. I assume, but I'm not sure.

Who does it know better then you ? You can verify with:

• Package: boot-info-script

What will happen to the MBR record on the system disk if I install the system on the SSD, and GRUB on the USB? Will the MBR of the system disk on the SSD remain in the same state as before the installation (without information about the system, only with the disk marking for the system). On the MBR of which disk will the information about the system itself be written?

It is possible to boot the computer from one disk (i.e. external USB disk) and load the operating system (Debian) from another disk. This is not very practical unless you have special requirements. The way to do it changes depending on the type of boot (legacy vs. UEFI).

There are solutions ready to use; i.e.:

• https://www.supergrubdisk.org/super-grub2-disk/

Another different solution is:

• Ventoy - A New Bootable USB Solution

Hope this helps.

Thanks Aki! Very useful links, but I will do this a bit later. My main question is - will the MBR of the disk with the system remain free from Boot system records, when booting from Grub from another disk, on a system with BIOS. Of course, I can practically check this, but maybe someone will tell me the details...

[Aki]

Hello,

My main question is - will the MBR of the disk with the system remain free from Boot system records, when booting from Grub from another disk, on a system with BIOS. Of course, I can practically check this, but maybe someone will tell me the details...

The MBR (Master Boot Record) of a hard disk remains free of boot system records as long as you don't write a boot loader to it: this is true for systems configured to boot in legacy boot/CSM mode.

The disk's MBR is not used by systems configured to boot in UEFI mode, because UEFI uses the boot disk's ESP (EFI System Partition) and the motherboard's NVM (Not Volatile Memory).

Hope this helps.