dual booting fc6, f8

[Gene Heskett]

On Saturday 22 December 2007, Mikkel L. Ellertson wrote:
>Gene Heskett wrote:
>> Greetings;
>>
>> In attempting to come up with a grub.conf which will boot either version
>> of the os, I kept running into not being able to boot f8 from anything but
>> a fedora kernel.
>>
>> I have successfully switched the kernel.org 2.6.24-rc6 kernel such that
>> all hard drives are now /dev/sd*.
>>
>> But I figured that would probably need an edit of /boot/grub/device.map,
>> but before I did that, I thought I'd run 'grub-install --recheck /dev/sda'
>> sda being the new name for the ide0,0 drive, the old /dev/hda.
>>
>>>From my read of the info page, I assumed it would not write anything, but
>> just check what was there for errors.  But it did
>> rewrite /dev/hda1/grub/device.map, placing fd0 above the older
>> assignments, and appending the new sata drive below as /dev/sdc, and
>> replaced a now missing FC2 install on what was /dev/hdb with the
>> /amandatapes drive which was formerly /dev/hdd.  There is currently no
>> drive on the middle connector of the first ide cable.
>>
>> Confusing ain't it?
>>
>> So, thinking that I needed to re-edit my grub.conf to set the f8 drive as
>> 'root (hd2,0)', I did so.  But now none of the f8 boot stanzas work, error
>> 15, file not found.
>
>Unless you have 3 hard drives that the BIOS sees, this should still
>be 'root (hd1,0)'. This tells Grub to use the second BIOS drive,
>first partition.

That's what I thought, but the 2nd bios drive is in fact a 350GB,
on ide cable 1, not 0, middle connector, so it would for ata style
access, be /dev/hdd, and there is no /boot partition on it, a gig
of swap & 20 GB of unused /var2, & the rest /dev/hdd3, is all for
amanda to use.  Its labeled, so it can show up anywhere in the ide
chain and be found ok.  There is a dvdwriter on /dev/hdc's ide1 end
cable position.  The bios itself, does not see this added sata card,
a vmlinuz/initrd combo must be loaded from one of the bios visible
drives, which makes the sata drive visible.  Booted to fc6/2.6.24-rc6,
a df looks like this:

[root at coyote mnt]# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                     149186740  82962776  58523484  59% / (was hda3 '/')
/dev/sda1               101086     62710     33157  66% /boot  (was hda1 '/root')
tmpfs                   518076         0    518076   0% /dev/shm
/dev/sdb2              9621880    152692   8980412   2% /mnt/var (was hdd2 '/var2')
/dev/sdb3            297068936 214856616  67122064  77% /amandatapes (was hdd3 '/amandatapes')
/dev/mapper/VolGroup01-LogVol00
                     376265916  65989744 290854580  19% /mnt/f8slash  (is sdc2)
/dev/sdc1               194442     31652    152751  18% /mnt/bootf8 (is sdc1 "/boot1"

So we have drives sca, sdb, and sdc (the sata drive on a via raid card)

But when booted by the above mechanism, using a fedora kernel to f8,
the drive order is scrambled, with the now sdc becoming sda, hda becoming
sdb and what was hdd is now sdc.

>> So I guess I don't understand how grub works as well as I thought.  The
>> info pages might tell me, but it seems the only way to read them is
>> backwards as once you've gone down a tree to read something, there seems
>> to be only one way to back up, using the backspace key, but you never get
>> back to the main menu so its easier to 'q'uit it and restart it, but that
>> screws with ones train of thought till not even 2 more cups of coffee
>> makes it make sense.
>
>Try using pinfo, and the arrow keys.

Thanks.  I could learn to hate either without much prompting.
>
>> The other ugly thought is that my bios doesn't see the sata drive (sdc) at
>> all, and the couple of times I made it boot to f8, I had to move all the
>> boot files to /dev/hda1, but specify /dev/VolGroup01/LogVol00 in the
>> kernel argument line, but that seems to have quit working too.
>
>The thing to keep in mind is that Grub uses the BIOS for all its
>drive access. So if the BIOS can not access a drive, then Grub can
>not access it. The Linux designation of a drive does not matter to
>Grub. Only the BIOS designation matters.

That's good info, but brings up a question:  Has the situation with
disk druid been alleviated or does it still have a mind of its own?
I'd like to tell it to use the ide drives first partition as its /boot
partition, which would immediately solve all that, but the last time
I tried such a trick, and I didn't have the format partition box checked,
it rewrote the partition table without the rest of a 160GB drives 5
other partitions.  By-by 120GB of data I had to pull off real dds2 tapes
at the time, took about a week and a near divorce.

Humm that brings up another question, of what use is
/boot/grub/device.map file then?  The 'grub-install --recheck'
re-wrote that file WITH the linux visible sata drive, like this:
(hd0)	/dev/sda
(hd1)	/dev/sdb
(hd2)	/dev/sdc

And with an fd0 entry as the first line I've since removed.

If the bios can't see sdc, that last entry serves no usefull purpose
and the --recheck code needs fixed, its buggier than a 10 day old
deer carcass in August.

DD has bit me one way or the other every time I get in the same room
with a copy of it.

This time I told it to use only the new sata drive and it actually
obeyed my wishes, a first I should probably go paint on an interstate
overhead sign.  Right now f8 is screwed a bit, I can't install fedora
kernel srcs so I can use the nvidia drivers installer (they aren't gpg
keyed), and it won't boot to f8 using this kernel because the drive
order is scrambled when compared to a fedora kernels find order.
Obviously there is some build option I have enabled that seems to favor
finding the ide drives and enumerating them first.  But from the
response to questions involving that, I have to assume there are
no previous tracks in the snow to follow.  Perhaps we will figure it
out, in which case this rambling thread may be of future use to someone.

As I've already copied 50GB of data, I'd druther not re-install,
but I think that's what its going to come to yet, and that will waste
another week by the time I let it update itself and recopy my data,
plus a touch ./autorelabel after I do, that's around 2 hours just
for that I found earlier this evening.

Many thanks Mikkel, and to anyone else who wants to jump in here
with pointers to helpfull info.

>Mikkel

Also, for those who celebrate it, Merry Christmas!

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
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