Missing Operating System on Poweredge 4300 (FC3)

[Aleksandar Milivojevic]

Jeff Vian wrote:

> If your /boot partition is on raid it cannot access the kernel to boot
> because the raid drivers are not loaded until after the kernel loads.
> 
> Kind of the chicken & egg scenario.
> 
> in general /boot must be on a plain partition, and then the rest can be
> on raid.

Not true.  /boot can be RAID1 partition.  I'm using similar setups since 
Red Hat 7.3 days.

To correctly setup grub on RAID1, he needs to install it correctly on 
both disks.

First, check grub.conf file.  Note if there is any "root" option 
inthere, and comment it.  You can't use "root" option with RAID1, but 
must let grub try to guess it correctly for you.  By default, it will 
use whatever partition it loaded stage1/2 from (usually, this is correct 
guess).  The reason is that root will specify an actual partition from 
where to load kernel.  You can specify only one partition there (on 
either first or second disk).  If you have both disks in the machine, 
all is fine.  But let say one disk goes south (or you simply disconnect 
it), and root option specified partition on that drive.  You wouldn't be 
able to boot.  If you leave it to grub to automatically detect it during 
runtime, in normal configurations it will do correct guess and always 
use the partition from the disk machine booted from.

Now, type "grub".  This will get you to the grub prompt.  You need to 
type rather long install line once for each disk.  I've split each of 
them into two lines here for readability (used "\" as line continuation 
caracter):

install --stage2=/boot/grub/stage2 (hd0,0)/grub/stage1 (hd0) \
         (hd0,0)/grub/stage2 p (hd0,0)/grub/grub.conf

install --stage2=/boot/grub/stage2 (hd1,0)/grub/stage1 (hd1) \
         (hd1,0)/grub/stage2 p (hd1,0)/grub/grub.conf

The lines are long because you want copy of grub that goes to the first 
disk to reference only partitions from the first disk, and likewise for 
the copy that goes to the second disk.

The parameters are highly installation dependant, so I'll go through 
each of them.

You can leave --stage2 as is.  Actually, you must.

(hd0,0) and (hd1,0) are references to boot partitions that contain grub 
configuration files and kernel.  Likewise (hd0) and (hd1) are references 
to disks.  If you have only two disks, they will be hd0 and hd1.  Most 
likely your boot partition will be (hd0,0) and (hd1,0) if you have only 
Linux installed.  The second number in (hd0,0) is partition number.  If 
your boot partition isn't on the first disk partition, simply change 
them to match what you have.  For example, if your boot partition is 
third partition, you'd change them to (hd0,2) and (hd1,2).  Usually, 
this would be the case if you have multiboot configuration (for example, 
Windows on first partition, and than Linux someplace else).

Now, a bit more complicated part.  Is your boot partition / or /boot? 
If you have separate partiton for /boot, than your boot partition is 
/boot.  If you don't have separate /boot partition (/boot directory is 
part of / partition), than obviously your boot partition is /.

If your boot partition is /boot (in other words, /boot lives on 
partition of its own), skip this paragraph.  If your boot partition is 
/, than you'd need to change paths following each (hd0,0) and (hd1,0). 
This is because that path is relative to the file system on the 
partition referenced.  If that is the case, just prepend /boot to those 
paths.  For example, in this case (hd0,0)/grub/stage1 would become 
(hd0,0)/boot/grub/stage1.  Change all other references likewise.  Do not 
touch path for --stage2 option, unlike other options, that one is 
relative to actual root file system and must begin with /boot!

Type exit, and you are done.

Sounds too complicated?  Well, you can always switch back to LILO.  LILO 
handles RAID1 automatically, out-of-the-box, no special setup needed. 
And frankly, I can't remember that I ever needed all those additional 
bells and whistles of Grub (that made it so darn complicated to use).

-- 
Aleksandar Milivojevic <amilivojevic at pbl.ca>    Pollard Banknote Limited
Systems Administrator                           1499 Buffalo Place
Tel: (204) 474-2323 ext 276                     Winnipeg, MB  R3T 1L7