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On 8/4/06, Meino Christian Cramer <Meino.Cramer@×××.de> wrote: |
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> Is this logically/technically correct, Richard: ? |
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> |
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> - The BIOS recogizes the "first" disk (grub: hd0) only by the bus it |
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> is attached to: A disk connected to "SATA connector 1" will be hd0, |
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> and another one connected to "SATA connector 2" will be hd1 |
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|
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It is based on the BIOS boot order mapping. So if the BIOS is |
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configured to boot connector 1 (c1) first, then c2, then yes, c2 will |
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be hd1. But if you remove c1, then c2 will be the first bootable hard |
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drive, and become hd0. |
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|
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> - Therefore grub can distinguish the disks and choose the correct one |
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> to boot from right from the BIOS settings and the bus ID even all |
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> disks attached to the system are physically and model-wise |
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> absolutely identical. |
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|
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If both drives are permanently connected, then you only need to |
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install grub on the first drive, and it can reference kernels and |
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initrds from the second drive (hd1). But if you are going to remove |
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the first one to boot from the second, or change the order of the |
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drives, then you will want hd0 in the grub configuration for both |
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drives. |
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|
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You can use device.map files to specify what the BIOS mapping will be |
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when you boot from each drive. So for example if you wanted to |
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install grub on /dev/sdb, and plan for it to become sda when you boot |
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from it, you can have a device.map that contains: |
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|
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(hd0) /dev/sdb |
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|
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And install grub on that device with: |
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|
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echo << EOF | grub --device-map=device.map |
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root (hd0,0) # assuming /boot is /dev/sdb1 |
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setup (hd0) |
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EOF |
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|
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> - So, booting a kernel image from the correct disk will be no |
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> problem. |
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> - Now...I will label the root of my bootdisk (grub: hd0) with "root" |
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> (only as an example...) and pass that as kernelparameter: |
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> |
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> root="root" |
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|
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For my recovery disk, what I use is "root=LABEL=recovery". You also |
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need an initramfs environment that uses the standard 'mount' command |
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to mount the root filesystem, so that the mount-by-label trick |
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actually works. |
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|
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Are you planning on removing one drive to boot from the other? Or |
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keeping both drives permanently installed and using BIOS/grub to |
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decide which drive to boot from? |
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|
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-Richard |
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-- |
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