September 8, 2009

Caution on GRUB with Ubuntu 9.10 (Karmic Koala) Alpha

I have mentioned this topic in passing before, when talking about Ubuntu Karmic GRUB, but I have since discovered that that issue is serious enough, or at least the consequences can be serious enough, that I think it deserves a separate and more detailed explanation.

During the installation of Ubuntu 9.10 Alpha 5, there are no questions about installing GRUB.  It does not ask if you want to install GRUB or not, or even where you want to install it, it quietly installs GRUB 2, and it installs it to the MBR (Master Boot Record) of your primary disk.  There are at least two specific things you need to be careful about related to this:

- First, and most important, if you intend to preserve your existing bootloader, meaning that you want to keep your MBR intact as it is, you are going to be surprised and disappointed.  Even if you install to a second disk, an external disk, or whatever, it will overwrite the MBR on your primary disk.  To be honest, I would love to be wrong about this because I think it is at the very least a bad idea, if not outright dangerous.  Certainly in the case of installation to a second disk, I would think that the very most it should do is install GRUB to the MBR of that drive, and not just silently modify your primary drive.  But I have tried the installation more than once, in several different systems and configurations, and this is what it has done every time.  Please, if I am wrong about this, someone tell me about it.

- Second, if you have a multiboot installation, and you are using Legacy GRUB for other Linux partitions, you are going to have to learn to deal with mixing the two versions of GRUB.  My blong entry, mentioned above, gives some more information about how to do this.


P.S.   According to the Release Announcement,  "GRUB 2 is the default boot loader for new installations".  This implies that if you upgrade an existing installation, it will not install GRUB 2, but since I never install an Alpha release as an upgrade (and it probably wouldn't be a good idea to do so in any case), I can't vouch for what it does in such a case.

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