Multibooting with Grub2

[Tom H]

On Thu, Oct 28, 2010 at 10:43 PM, Liam Proven <lproven at gmail.com> wrote:
> On Fri, Oct 29, 2010 at 3:41 AM, Liam Proven <lproven at gmail.com> wrote:
>> On Wed, Oct 27, 2010 at 6:20 AM, Tom H <tomh0665 at gmail.com> wrote:
>>> 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".
>>
>> I think that, unfortunately, the 1st distro I tried is based directly
>> off Debian, not off Ubuntu any more, and sadly, this appears to mean
>> that Grub1 was no longer an option. There was no package for it in
>> Synaptic, so I went with Lilo.
>>
>>> 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".
>>
>> Aha! I didn't know that. Thanks, very useful tip.
>>
>> Since I do not own a hard disk bigger than 150GB, I never choose ext4,
>> always ext3, but I may have left some installations on defaults and
>> that can mean ext4 now.
>>
>>> 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.
>>
>> Good to know. Thanks again.
>>
>>> You can only have one grub2 "active" in the MBR but you can chainload
>>> with either chainload or configfile to the other grub2 installs.
>>
>> I have tried this, but never got it working reliably.
>>
>>> 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)".]
>>
>> I find I cannot mount my BSD partition. I have installed the UFS
>> utilities and can even fsck it, but I can't mount it. I've tried
>> ``mount'', ``mount -t ufs'', & ``mount -t ufs -o=ufs2'' (or something
>> like that) - nothing works.
>>
>> *But* it suddenly occurs to me - with FreeBSD 8, which PC-BSD 8.1 is
>> based upon, there are multiple slices within that 1 primary partition.
>> Maybe I need to mount slices directly. I don't know how to do that.
>>
>> Why can't BSD just play the game, like other PC OSs, and just
>> understand & use the PC partitioning system directly? >_<
>
> Sorry, I forgot - what I /was/ going to say was: if Linux can't mount
> the partition, does that not mean that Grub can't look inside it and
> see what kernels or whatever are in there for Grub to add to its boot
> menu?

Yes. update-grub fails because it considers the partitions faulty.