Grub disk: something automatic?
ubuntu at tigershaunt.com
Thu Jan 28 14:24:55 UTC 2010
Dotan Cohen wrote:
>> Dotan, if we are talking only of grub-legacy not grub2, then at grub
>> prompt do a 'root' and 'setup' like
>> root (hd0,x)
>> setup (hd1)
>> But watch out for mapping if harddrive is not the master drive
>> Also you would need to update-grub first for that (hd,x). You cannot do
>> that at grub-prompt.
> The problem is that I often cannot boot, so I cannot perform
> update-grub. Also, most of my machines (other than the laptop) have
> multiple hard drives.
Hi Dotan, sorry I do not have an exact answer for you, but here are some
suggestions to help with your situation. Multiple hard drives can be a
pain on modern Motherboards, because the Mobo can re-assign drive
numbering on boot, (if you boot from CD-ROM on one controller then
switch to a SATA hd on another controller, drive numbering between your
IDE and SATA hard drives will be completed messed up. Here are some
strategies to alleviate the headaches:
1. If possible, arrange your hard drives so your primary linux partition
is on your boot hard drives. When bootstrapping grub, disconnect the
other hard drives. It's impossible for even grub to mix up the hard
drive numbering when there is only hd0. It will not matter how badly
device.map is inaccurate on future update-grub runs, since grub will now
auto-fix itself based on UUID's.. (I'm really loving this new feature.)
2. Install grub on the super-block of your filesystem as well as the
mbr. (this won't work with XFS filesystem, since XFS does not leave
space on the superblock)
ex: grub-install /dev/sda1
Then mark that partition as bootable in your partition editor.
That way, whenever another OS or disk utility messes your MBR, *any*
bootloader or repair disk will be able to chainload your grub that is
safely installed on the partition. From the lowly dos fdisk /mbr (or
lilo -m /dev/sda) to simply install an old style dos MBR will be enough
to get your linux booting again.
While reading the grub documentation, I also saw reference that grub can
now create it's very own boot partition to deal with these musical hard
drive situations, which should be more reliable. I haven't tested this
myself yet (on to-do list) so can't offer guidance, but it's worth
perusing the grub documentation wiki.
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