I have a computer with grub and linux installed on the internal hard drive. I also have a USB flash drive with linux that I boot into with grub on the internal hard drive. This causes the USB flash drive to always be /dev/sdb. I would like to know, if I have GRUB on the USB flash drive and boot to it via the BIOS menu, will it be seen as /dev/sda instead of /dev/sdb?

  • My computer that I'm typing on its booting from /dev/sdb Feb 1 at 17:55

1 Answer 1


No, it depends on the disk. For new SSD via nvme for instance the disk is called nvme0n1. And if you have also a SATA disk you can also have a sda disk which is not the boot drive.

As far as I know nothing prevent the computer from booting on sdb or something else, you can by the way configure the bios to use one disk in particular for booting.

  • Oh, ok. Will I be able to assume then that if I plug it into a computer that had no other USBs plugged in, it will be /dev/sdb? Feb 1 at 14:59
  • You can assume it, but there is no guarantee that it is the case. I am not sure how are decided the names (sda, sdb, etc. ) but it is the OS who does that. Also, the priority of boot is defined in the BIOS.
    – vinalti
    Feb 1 at 15:05
  • What is your use case ? What do you want to do with sdb ?
    – vinalti
    Feb 1 at 15:05
  • I have an LFS (Linux from scratch) installation on a flash drive, and the grub.cfg needs to point to a specific drive in order to boot the correct OS Feb 1 at 15:09
  • 1
    Is it a UEFI install or BIOS install? UEFI using gpt partitioning requires an ESP - efi system partition for grub's boot files. If old BIOS you can boot just by installing grub to MBR. But if using gpt and BIOS need a tiny 1 or 2MB unformatted partiiton with bios_grub flag ( if using gparted).
    – oldfred
    Feb 1 at 18:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.