grub question [Solved]

[apiaio]

Hi there!
After installation SL I edited grub.conf, because of dualboot. Up to now I used LILO and command /sbin/lilo
overwites MBR. I do not know how to do that when using grub. Following Gentoo Handbook I used comman

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grub-install

but

-bash:grub-install: command not found

was the response.
Thanks

[micia]

Hi!

check out:
(as root)

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grub2-install --help


[Edit]
by the way, if you need to edit the configuration of GRUB2, you have to edit:
/etc/default/grub
and use:
make a backup of the existing /boot/grub/grub.cfg before executing this command
(as root)

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grub-mkconfig -o /boot/grub/grub.cfg


to update /boot/grub/grub.cfg since now the GRUB configuration is stored in that file.

there should be no need of using grub2-install directly in this situation.
[Edit end]

the guide that you are using now is probably intended for GRUB prior to version 2.

[apiaio]

I have installed grub-1.98.I used

grub-mkconfig -o /boot/grub/grub.cfg

but nothing has changed after reboot

[joost]

You most likely want to run:

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grub2-install

That will install grub2 to MBR. If you haven't done this already, generate a grub.cnf file:

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grub-mkconfig -o /boot/grub/grub.cfg

fyi grub2 doesn't use grub.conf anymore.

[apiaio]

fyi grub2 doesn't use grub.conf anymore.

In which config file I can set the boot conditions after installing grub2?
E.g. I will start windows from sdb1. AFAIK I will need to use something like that

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...
title Windows
root (hd1,0)
map (hd1) (hd0)
map (hd0) (hd1)
...

[joost]

No idea how that works with grub2.

[Fitzcarraldo]

GRUB 2 uses the package sys-boot/os-prober to find out which other OSs are installed. In my case it generates automatically the following section within the /boot/grub/grub.cfg file when I run the grub-mkconfig -o /boot/grub/grub.cfg command:

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### BEGIN /etc/grub.d/30_os-prober ###
menuentry "Windows 7 (loader) (on /dev/sda1)" {
        insmod ntfs
        set root='(hd0,1)'
        search --no-floppy --fs-uuid --set a6863e9f863e7043
        chainloader +1
}
menuentry "Windows 7 (loader) (on /dev/sda2)" {
        insmod ntfs
        set root='(hd0,2)'
        search --no-floppy --fs-uuid --set a2243da8243d7ff9
        chainloader +1
}
### END /etc/grub.d/30_os-prober ###

So it detects automatically my two Windows partitions. If you run the aforementioned grub-mkconfig command it should automatically detect your Windows partition on /dev/sdb1 if you have sys-boot/os-prober installed (if you don't have it installed, it does nothing).

You can also disable automatic probing by adding the line GRUB_DISABLE_OS_PROBER=true to the file /etc/default/grub before running the aforementioned grub-mkconfig command.

You can override the automatic os-prober by instead editing the /etc/grub.d/40_custom file before running the aforementioned grub-mkconfig command. See the example for a Windows partition on the second drive, given in Section 3.2.1 of the Gentoo Wiki article on GRUB 2.

Look in /boot/grub/grub.cfg after running the aforementioned grub-mkconfig command to check if everything worked. If not edit the input files mentioned above and re-run the command.

(Strictly speaking, you are not supposed to edit the /boot/grub/grub.cfg file. However, in practice many people do. Your choice, but be aware that whatever edits you do to that file directly could be overwritten if either you or something else -- such as an Entropy kernel upgrade -- runs the grub-mkconfig command.)

[joost]

The problem is that you need to remap the drives because Windows needs to be on the first harddrive otherwise it will fail to boot. Not sure how mapping is done in grub2 and if it still is needed (or grub2 does that automagic)

[Fitzcarraldo]

See remapping example in /etc/grub.d/40_custom file in Section 3.2.1 of the Gentoo Wiki article on GRUB 2 that I linked to.

[joost]

Ah there we go.