Multibooting with Grub2

Tom H tomh0665 at
Fri Oct 29 04:00:13 UTC 2010

On Thu, Oct 28, 2010 at 11:07 PM, Nataraj <incoming-ubuntu at> wrote:
> On 10/28/2010 07:43 PM, Liam Proven wrote:
>> On Fri, Oct 29, 2010 at 3:41 AM, Liam Proven <lproven at> wrote:
>>> On Wed, Oct 27, 2010 at 6:20 AM, Tom H <tomh0665 at> wrote:
>>>> On Tue, Oct 26, 2010 at 9:37 PM, Liam Proven <lproven at> 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/", "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? >_<
>> chacun á son goût
>> 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?
> Is this a standard extended partition?  If you run 'fdisk -l' or gparted
> does the partition show up?  If not, then I would think that you won't
> be able to access it, at least using standard mount commands and system
> utilities.  If it's there then I would think you should be able to mount
> it if linux has a driver for the file system format.

If the bsd disk is /dev/sda (in Linux), run "fdisk /dev/sda"

"p" displays the slices

"b" then "p" displays the bsd partitions of the slices

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