Re: software mirroring of boot drive

[Dominic Rivera <dominic semicolonpee com>]

If you want to use grub take a look at /boot/grub/device.map which will show you all of your available devices in grub. Assuming that your 1st partition contains your /boot you can do the following to set up grub on the second drive to read the contents of the second drive when booting. I have had the problem previously when grub-install would write the MBR to look at the first drive that I installed grub on (sda), which really wasn't very helpful when booting from sdb.:

<x-tad-bigger>[root localhost grub]# grub</x-tad-bigger><x-tad-bigger>
Probing devices to guess BIOS drives. This may take a long time.


GRUB version 0.93 (640K lower / 3072K upper memory)

[ Minimal BASH-like line editing is supported. For the first word, TAB
lists possible command completions. Anywhere else TAB lists the possible
completions of a device/filename.]

</x-tad-bigger><x-tad-bigger>grub> root (hd1,0)</x-tad-bigger><x-tad-bigger>
Filesystem type is ext2fs, partition type 0x83

</x-tad-bigger><x-tad-bigger>grub> setup (hd1)</x-tad-bigger><x-tad-bigger>
Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... yes
Checking if "/grub/stage2" exists... yes
Checking if "/grub/e2fs_stage1_5" exists... yes
Running "embed /grub/e2fs_stage1_5 (hd1)"... 16 sectors are embedded.
succeeded
Running "install /grub/stage1 (hd1) (hd1)1+16 p (hd1,0)/grub/stage2 /grub/grub.conf"... succeeded
Done.

Now if you want to have this all get setup in a kickstart, add this to your %post section

# Install the bootloader onto both hard drives
/sbin/grub --batch <<EOF 1>/dev/null 2>/dev/null
root (hd0,0)
setup (hd0)
root (hd1,0)
setup (hd1)
quit
EOF
</x-tad-bigger>
On Jun 25, 2004, at 9:16 AM, Grunloh, Robert wrote:

> Hi,
>
> you all were so good at answering my last beginner question, I have another.
> I'm trying to set up a rhel 3 server with 2 18gig scsi drives, where each
> disk has the entire os and mirrors the other, so that we have no downtime if
> either drive fails. The machine doesn't have hardware raid, so I've
> partitioned it as sda1 & sdb1 /boot and sda2 & sdb2 /  and then created md0
> and md1 during the install (raid 1). From what I can tell everything is
> working once booted.
>
> However if, as a test, I tell the scsi card's bios to boot off of the 2nd
> drive it just hangs (no errors) before the grub menu appears. Same behavior
> if I unplug the first drive. If I unplug the 2nd drive it boots ok but
> complains about degraded mode, as expected.
>
> I suspect the partitions are mirrored but grub isn't properly installed on
> the second drive's MBR or isn't aware of it. However I can't seem to
> unmirror them to work on the problem, since they're in use, not that I'm
> good with grub anyway. -- I must be missing something obvious.
>
> This isn't a config I'm especially in favor of, but I've been assigned to
> get it working if possible. Can anyone point me to some howtos or faqs? I've
> searched but found only older docs for lilo, and a nice IBM article covering
> pservers. This box is a dell PE2500, but I'm testing now on a generic old pc
> with adaptec card.
>
> thanks much
> Robert Grunloh
> University of Arizona Library
>
> -------------------------------
> "Very few of us know how much we have to know in order to know how little we
> know."
>
>
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Dominic Rivera (dominic semicolonpee com)
(503) 810-9408
6233 SW Arbor Grove Dr
Corvallis, Or 97333