Need Clarification on Grub Settings

English Install/Boot/Login
1

During the final stage of installation where a summary of the Installation Settings http://imageshack.us/photo/my-images/41/grub.png/, noticed that :

any idea how “Boot from MBR and / partition” will affect the booting?
which is the “correct” setting?

any links or clarification appreciated, thanks.

2

According to your picture, you’re installing on a virtio disk (vda) but the info reported under Booting in the Installation Settings apply to a sata or IDE disk (sda). There is something strange here. If you’re installing on a vm, you should see something like this: http://www.unixversal.com/linux/opensuse/images/opensuse_vm_install39.jpg

Of course either Boot from “/” or Boot from MBR should be enabled … or even both.

To see an example of an installation into a virtual machine (kvm in this case), have a look on the slideshow on this page: openSUSE 11.4 - vm installation guide

If you’re not installing in a virtual machine, there is something weird with this installation… or the virtio driver is used for other devices, which I don’t know.

3

In case you are installing to a physical drive, installing to the MBR will wipe your current Boot Record and replace it with Grub. Installing Grub to the / directory is more of a setup for another bootloader to call this install. A bootloader in the / partition won’t boot itself. For example, I install Grub to the / partition always and add an entry for Linux into my Windows Boot Loader instead of overwriting the MBR.

4

Thanks for the reply.

First off, the image was taken from Novell’s document, so isn’t really the actual condition (should be sda instead of vda)

Have been installing openSUSE without much conscious attention to this “Installation Settings” summary page.
Only realized the default setting when a friend asked specifically about the meaning of these

  • Boot from MBR is disabled
  • Boot from “/” partition is disabled
    that I was sort of confused.

Just installed a laptop and a netbook with openSUSE 11.4 and both cases, they are defaulted to disabled

Isn’t this a bad default?

Or am I missing something (like there is no difference if it is disbled or enabled)?

5

Boot from MBR means that the Grub bootlader will be installed into the first sector of disk (Master Boot Record). In that case, it will be booted when you turn on the computer, no matter which partition has the bootflag.
Boot from “/” partition means that the Grub bootloader will be installed in the boot sector (first sector) of the Linux root partition. In this case (actually NOT under this condition but in the absence of the other condition), YaST will write a generic bootcode to MBR and set the bootflag on this parition, so that it will be booted by default.

The only explanation I can think of is that you’re installing Linux in a logical partition, so neither the MBR nor the root partition will be booted (contain Grub stage1) but the extended one … Posting a “wrong” picture doesn’t help to make it clearer though.

Here’s what I have BEFORE changing the defaults: http://www.unixversal.com/linux/opensuse/images/opensuse_vm_install40.jpg

If you’re asking me, YES. But I bet you’re not just asking me. :wink:

6

please_try_again ,

thanks, that clears the doubts lol!