Re: /boot shared between different Linux installs?

[Andrei Borzenkov]

On Fri, Apr 22, 2016 at 4:20 PM, drsmith <address@hidden> wrote:
> Thanks for the input.  This system has grub 0.97 and I forgot to mention
> that in the original message. Some things may need to be tweaked to be
> compatible.  This is because commercial software rarely lets you use the
> latest and greatest version or it's not supported.
>
> Also, I'm thinking the references to hd0,msdos2 should probably be
> hd1,msdos1 because it is a different disk, rather than a different
> partition.
>
> Are the msdosN references 1 based?

In GRUB legacy this would be

rootnoverify (hd1,0)
chainloader +1

It counted zero based.

  Seems odd when the hdN references start
> from 0.
>
> thanks.
>
> On Thu, Apr 21, 2016 at 11:28 PM, Andrei Borzenkov <address@hidden>
> wrote:
>>
>> 21.04.2016 22:00, drsmith пишет:
>> > I'm currently working on installing a server with two logical drives in
>> > it:
>> > sda and sdb.  Each logical drive is going to get an installation of
>> > Linux
>> > and each install has a different purpose.  The first install is mostly
>> > used
>> > for recovery scenarios while the second would be the production
>> > installation.
>> >
>> > The issue I've run into is that I have two /boot partitions, but the MBR
>> > of
>> > the first disk only points to one grub.conf file.  Manually keeping
>> > these
>> > synchronized isn't something I'd like to do if I could avoid it.
>> >
>> > Either I have to have one shared /boot partition that gets mounted by
>> > both
>> > installations or I have to figure out how to get grub to chainload
>> > itself
>> > from the second drive.  In the chainload scenario, you would see two
>> > menus
>> > where choosing the install on the second hard drive gives you the menu
>> > for
>> > that installation.
>> >
>> > I've run this through the stack-exchange sites and I've tried many
>> > searches
>> > over the past few days, but information on this seems to be rather
>> > scarce.
>> > Maybe I'm not thinking of a better possibility.  Any insight you could
>> > offer would be greatly appreciated.
>> >
>>
>> Assuming that second GRUB is installed in partition, this would be
>> something like
>>
>> menuentry "Chainload GRUB from second partition" --id some-unique-uuid {
>>   set root=hd0,msdos2
>>   chainloader +1
>> }
>>
>> In this case boot sector is in the second partition boot block. I would
>> recommend following practice of searching for partition instead of
>> hardcoding device name, so if this partition has file system (e.g. it is
>> /boot partition of second install), it would be something like
>>
>> menuentry "Chainload GRUB from second partition" --id some-unique-uuid {
>>   set root=hd0,msdos2
>>   search --set --hint-bios=hd0,msdos2 --fs-uuid <file-system-uuid>
>>   chainloader +1
>> }
>>
>> where FS UUID can be obtained by running in Linux
>>
>> grub-probe -t fs_uuid /boot
>>
>> (may be grub2-probe depending on distribution).
>>
>> It is highly recommended to give each menuentry unique ID (grub-mkconfig
>> does it) which can be used later as reference in setting default boot
>> choice. Advantage is, this is independent of relative order and allows
>> adding and removing menu entries while preserving chosen default.
>>
>> You can also load directly core.img without installing it, using
>>
>> multiboot /boot/grub/i386-pc/core.img
>>
>> Using current version (2.02~beta3) this core.img is created by
>>
>> grub-install --no-bootsector
>
>
>
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