GrubHardDiskOrder

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Contents

Other titles for this same problem.

  • Grub Hard Disk Order
  • GRUB Hard Disk order does not meet by BIOS boot sequence
  • I do not know what's the correspondence between my Linux devices and my grub devices

Introduction

Even if you know where all your hard disks are plugged in this does not mean anything about its order. There are some bios that give a different hard disk order when you boot super grub disk from a cdrom than when you boot from your hard disk. There are some hard disks that Super Grub Disk cannot see because your own BIOS cannot see. Sometimes BIOS offer the same hard disk twice, so that the first and the second hard disk are in fact the same hard disk (probably the first one).

In this webpage we will try to explain all these concepts and the Super Grub Disk tools you can use for fixing your system without too much problems.

Linux devices

One command that you can use for knowing what are your devices from the Linux point of view is:

sfdisk -lu

This command will show you all your hard disks and your partitions even your usb pendrives. hda means primary master sda means first scsi disk although nowadays it means first sata disk.

Grub devices

I am working on a sfdisk -lu equivalent for Super Grub Disk but while I develop it you can use:

  • Choose Language & Help
  • English Super Grub Disk
  • Boot & Tools
  • Show Partitions

The first screen shows all the hard disk devices.

Once you select one of the partitions you will see another list with all of its readable partitions (i.e. you do not see extended partitions). This list contains:

  • Device grub name
  • Device grub name supposing it was an scsi one and that BIOS and linux order did match.
  • Device grub name supposing it was an ide one and that BIOS and linux order did match.
  • Filesystem (EXT2FS means EXT3)
  • Os name (Windows if FAT32 or NTFS found. The distro name is shown if /etc/issue is available.)
  • Size (TO COME SOON... NOT CURRENTLY SHOWED).

If you select one of this partitions you come back to the Show Partitions menu.

By repeating this operation with all your hard disks you will be able to make mental map between the Linux devices and your Grub devices.

Hard Disk Bios Order

Some BIOS let you change the default hard disk order so that instead of the primary master hard disk being the first one to boot (hd0) the secondary master hard disks becomes the first one to boot.

This usually has a direct influence to Grub, when refering to (hd0) you are selecting another hard disk than the default one.

How to Tweak Hard Disk Boot Order in Super Grub Disk

Easy Live Swap

If your pc has only two hard disks and you check them with the Show Partitions option and you see that super grub disk is not listing the correct order compared to the default bios boot order you can easily tweak its order.

Either you choose:

  • EASY LIVE SWAP

from the quick menu either you choose:

  • Choose Language & Help
  • English Super Grub Disk
  • Boot & Tools
  • Live Swap
  • Easy Live Swap

Live Swap

If your pc has three or more hard disk and you check them with the Show Partitions option and you see that super grub disk is not listing the correct order compared to the default bios boot order you can tweak its order.

Let's suppose that your hda, hdb, and hdc hard disks are detected as: (hd2), (hd1) and (hd0) and you want them to be detected the other way round.

You can choose:

  • Choose Language & Help
  • English Super Grub Disk
  • Boot & Tools
  • Live Swap
  • Simple Live Swap
  • Select: (hd0)
  • Select: (hd2)


  • Simple Live Swap
  • Select: (hd2)
  • Select: (hd0)


  • Live Swap!

Or you also choose:

  • Choose Language & Help
  • English Super Grub Disk
  • Boot & Tools
  • Live Swap
  • Double Live Swap


  • Select: (hd0)
  • Select: (hd2)


  • Live Swap!


for the swap.

Shift Live Swap

If you have three drives and you want to shift all the drives a position so that (hd1) becomes (hd0) and so on:

  • Choose Language & Help
  • English Super Grub Disk
  • Boot & Tools
  • Live Swap
  • Simple Live Swap


  • Select: (hd0)
  • Select: (hd1)


  • Simple Live Swap


  • Select: (hd1)
  • Select: (hd2)


  • Simple Live Swap
  • Select: (hd2)
  • Select: (hd0)

Usbshift

Usbshift is a command that it is run automatically at the boot of Super Grub Disk. Its behaviour is the following one: If Super Grub Disk is being run from (hd0) device (usually when you run it from a usb) then a shift of all the drives is done. This way the second hard disk becomes the first hard disk (what it is usually). And the pendrive device (the device with SGD in it) becomes the last grub device.

If Usbshift does not detect that SGD is being run from (hd0) it does nothing.

You are not supposed to run usbshift yourself but you should know about it because if you are used to create your own menu.lst for usb you will probably think that (hd0) means usb while in SGD it only means first hard disk.

Problems related to the Grub Hard Disk Order

Installation of Linux does not boot

Examples

Onederer and their two hard disks nightmare