Re: managing a multiboot without stomping the toes of other OSes

[Rustom Mody]

On Fri, Jan 14, 2011 at 3:40 PM, Felix Miata <address@hidden> wrote:
> On 2011/01/14 14:43 (GMT+0530) Rustom Mody composed:
>
>> I have a system with ubuntu on sda5 and debian on sda6 and a dedicated
>> grub partition on sda3 (mbr points to sda3)
>> The sda3 grub.cfg only chainloads to sda5 with title ubuntu and
>> likewise sda6 with title debian.
>> Further bootsector grubs in sda5 and 6 manage the detailed linux options.
>
>> The problem is that whenever some package is updated (eg grub-pc) it
>> 'detects' other OSes and makes a grub.cfg with all kinds of junk such
>> as the debian kernel with the ubuntu filesystem etc etc.  What is
>> worse, it meddles with the sda3/mbr grub
>
>> So what I want is that I should be able to tell the Debian grub:
>> 1. You are sitting on sda6 (not sda)
>> 2. So please leave sda alone
>> 3. Please dont 'detect' other OSes
>
> Put in each /etc/default/grub:
>
>         GRUB_DISABLE_OS_PROBER=true
Ok Ill try that
>
> As extra insurance, I've been removing:
>
>        /etc/grub.d/30_os-probe*
>
> Since I'm a mostly a non-Debian user and I've always remembered to specify /
> or /boot as a Grub target during OS installation, I've never yet needed to
> move a Grub2 location or figure out how it's done. NAICT, one would do this
> by specifying the /boot or / target as a device name running grub-install.
> See: https://help.ubuntu.com/community/Grub2
>
> Another option to consider is installing grub-legacy to sda3 and/or mbr and
> using its chainloader to reach sda5 & sda6. Typically I pre-partition and
> boot a Knoppix disk to mkfs and install Grub1 on a virgin HD before
> installing any operating systems. On multiboot systems I keep a separate
> realboot /boot partition that I never mount as /boot and from which I either
> load default kernel/initrd sets from specified partitions, or chainload to
> specified partitions.
>
> One can always expect stepped on toes when multibooting and accepting the
> usual installation default to install a bootloader to the MBR. Thus I find
> MBR as default bootloader location as policy to be ludicrous. Any OS that
> insists on MBR as bootloader location I abort and/or eradicate from my
> systems. Grub on MBR is rarely necessary. I've never needed it, while I have
> many machines with up to 25 or more installed operating systems.

I really dont understand (many things actually:-) )
If there is not a bootloader in mbr how does the machine boot?
Furthermore when grub-installing to /dev/sda6 (instead of /dev/sda)
I get all kinds of ominous warnings and what not and grub wont do it
until I give a --force option.  This seems to be the opposite
direction of what you are saying (or else I dont understand)