Need to move GRUB

[Karl1982]

I changed out my laptop's hard drive recently. It used to have Ubuntu and Windows 7. Usually the way I like to do this is have Ubuntu install GRUB to its own partition boot sector so 1.) Windows will leave it alone, and 2.) I can later replace the boot loader with GRUB4DOS and chainload the partition directly, thus getting Ubuntu's original GRUB menu. That way Ubuntu can update/modify its own GRUB config (including new kernels and arguments) as it sees fit and I don't have to worry about it.

I decided to go with a clean installation since my previous one had been through a few distro upgrades. I haven't even put Windows on it yet, but on my new Ubuntu installation, I accidentally let it install GRUB to sda instead of sda1, so it wrote it to the MBR instead of its partition BS. I dropped GRUB4DOS on it anyway, and I could directly load the kernel or the GRUB core... but next time GRUB updated, it blew out my GRUB4DOS on sda and replaced it with its own GRUB again.

Basically, I want to reinstall/retarget GRUB to sda1 so I can get things back how I want them, and I'd like to do it without having to reinstall. I know my way around GRUB4DOS, but I'm not very familiar with GNU GRUB. I was afraid I might do something that would mess up the way Ubuntu is updating its own GRUB config. It's Ubuntu Desktop 10.04 with GNU GRUB 1.98-1ubuntu7. What do I need to do?

[oldfred]

I have learned to like grub2, but it is more complex because it offers more features.

Grub2 does not like to be installed to a partition as then you have to use blocklists. As I understand it a blocklist is hard coded addresses, so if your boot files get moved on an update (or even by a filecheck) then boot will fail. You would have to reinstall to fix. I think they are trying to make it more difficult but the old procedure was to add --force to the install command.

Attempting to install GRUB to a partition instead of the MBR. This is a BAD idea.
Embedding is not possible, GRUB can only be installed in this setup by using blocklists. However blocklists are UNRELIABLE and its use is discouraged.
error: If you really want blocklists, use --force


General info:
http://www.gnu.org/software/grub/manual/
The Grub 2 Guide (formerly Grub 2 Basics)
http://ubuntuforums.org/showthread.php?t=1195275
https://help.ubuntu.com/community/Grub2#Reinstalling%20GRUB%202

[Karl1982]

To be clear, I'm talking about on the last screen of Ubuntu installation, there is a button (Advanced, if I recall) that allows you to specify where to install the GRUB boot loader. I've selected sda1 instead of sda on several installations of Ubuntu and never had a problem, even after distro upgrades.

But you're telling me this is an unstable configuration? grub-setup --help even uses this as an example: DEVICE must be a GRUB device (e.g. `(hd0,1)').

So if I run sudo grub-setup (hd0,1), leaving everything as defaults, it'll install the boot code to its partition bootsector (that is the correct device and partition), and leave the existing GRUB config files untouched? Or do I want to use grub-install? I also need it to not overwrite GRUB4DOS when GNU GRUB is updated in the future.

[confused57]

To be clear, I'm talking about on the last screen of Ubuntu installation, there is a button (Advanced, if I recall) that allows you to specify where to install the GRUB boot loader. I've selected sda1 instead of sda on several installations of Ubuntu and never had a problem, even after distro upgrades.

But you're telling me this is an unstable configuration? grub-setup --help even uses this as an example: DEVICE must be a GRUB device (e.g. `(hd0,1)').

So if I run sudo grub-setup (hd0,1), leaving everything as defaults, it'll install the boot code to its partition bootsector (that is the correct device and partition), and leave the existing GRUB config files untouched? Or do I want to use grub-install? I also need it to not overwrite GRUB4DOS when GNU GRUB is updated in the future.

If this is what you need or want to do you can run:

sudo dpkg-reconfigure grub-pc
then just select your Ubuntu partition(e.g. /dev/sda1) to install grub to, when update-grub is run. As long as Ubuntu 10.04 with grub2 is on a primary partition, you should have no problems chainloading to it...I haven't been able to chainload to 10.04 on a logical partition.

[Karl1982]

That's exactly what I needed, thank you.