Multibooting with Grub2

[Tom H]

On Tue, Oct 26, 2010 at 9:37 PM, Liam Proven <lproven at gmail.com> wrote:
>
> I am setting up a multiboot PC for testing. It has FreeBSD 8.1, Ubuntu
> 9.04, 10.10 and Debian 5, so far. I plan to add more.
>
> The snag is the 'buntus and Debian all want to run Grub2, & Grub2 only
> wants to go in the MBR. I don't want it in the MBR - it means that if
> I am in 1 distro & get a kernel update, the Grub from the other distro
> doesn't see it. Only 1 copy of Grub2 can be active at a time.
>
> I want a bootloader in each OS's root partition and a separate 3rd
> party one in the MBR. Currently I'm using XOSL in a tiny 32MB FreeDOS
> partition, but it can't boot the Linuxes 'cos their Grub2s have gone.
>
> Grub2 issues terrifying warnings if I try to install it to the
> partition instead of the disk. Is this in fact safe?
>
> Grub1 seems to be deprecated and missing in 10.10 and Debian "Lenny" -
> the choices are Grub2 or LILO.

grub1 is still available, as "grub". Don't forget to have a separate
ext2/3xt3 "/boot" or to have an ext2/ext3 "/" if you use
grub/grub1/grub-legacy rather than grub2 because grub1 can't handle an
ext4 "/boot".

You don't have to install grub2 to the MBR. The installed even offers
to install to a partition now; it might use block lists but I'm not
sure about that.

You can only have one grub2 "active" in the MBR but you can chainload
with either chainload or configfile to the other grub2 installs.

There was just a thread in help-grub where someone couldn't load
FreeBSD with grub2. I've just tried in three VMs (Maverick, Natty, and
Sid) and didn't get anywhere and the OP has posted that he found a
thread in grub-devel which said that there were problems with freebsd.

[FYI, when I attach the FreeBSD disk to one of the other VMs, the BSD
partitions are detected (they are listed with "dmesg | grep bsd"),
grub-mkdevicemap adds the disk to "/boot/grub/device.map", "grub-probe
--target=drive --device /dev/sdb5" lists the disk as "(hd1,msdos1)"
(strangely not "(hd1,msdos1,bsdX)", but neither update-grub nor
os-prober (the same thing, I know, but I thought that I'd check
anyway) detect it. At the grub cli, ls lists "(hd1,msdos1)" and
"(hd1,msdos1,msdos4)".]