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Old 08-02-2005, 02:10 PM   #1
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Question Error Loading Operating System

I recently purchased a Dell Precision 530 workstation and installed WhiteBox Ent. Linux 4 distribution (RHEL4 variant). Since I have two SCSI drives, I installed the system using software RAID. Plus, I'm running LVM. Everything has been working fine for approximately 6 weeks - the system has been rebooted several times without problems. However, when I attempt to boot now, the system runs through the SCSI adapter checking all of the LUNs (which is normal) and then I get the "error loading operating system" error. The only system changes have been kernel mods required for Oracle.

I am able to boot from the linux cd (linux rescue) and the operating system on the hard disk(s) is found. I do have a separate /boot partition, but can't remember if grub was required during the install. When the system was booting properly, I did get the option to choose which kernel I wanted to boot from, but I don't know if that was part of grub or just the OS.

I've googled this to death, but have mostly found issues related to dual-booting with XP. Since I'm using SCSI drives, RAID, and LVM, I haven't come close to finding issues related to my situation. I'm ready to re-install, but I'd really like to figure this out instead of caving in.

Thanks for any help you can provide.

Old 08-02-2005, 08:55 PM   #2
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'Error loading operating system' comes from BIOS. This means your GRUB is gone from MBR. I think booting up using rescue disk and rewriting your MBR would solve your problem. Reinstalling OS is really not necessary.
Old 08-03-2005, 02:41 AM   #3
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Ok. When I boot from the rescue cd and chroot /mnt/sysimage, I can see all of the files in /boot/grub and that all looks good: grub.conf is linked to menu.lst, etc. After noodling around some more, I found a similar issue which led me to the following commands:

# grub
grub> find /boot/grub/stage1

grub> find /boot/grub/stage2

grub> quit

Keep in mind that the system has only 2 scsi drives, sda & sdb and there are 2 raid 1 partitions. A 'df' shows that /boot is mounted on the raid device /dev/md1. /dev/md0 appears to be the raid device for all of the logical volumes that make up the rest of the system. I've tried to run 'grub-install' on /dev/md0, /dev/sda, /dev/sda1, etc., but it always returns with "/dev/md1 does not have any corresponding BIOS drive".

Is grub-install the correct command to use? I did not make a backup of the MBR as I've seen done in some of my findings. Not sure what else to try.

Thanks again for the help!
Old 08-06-2005, 12:44 PM   #4
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I tried to copy the MBR from another linux server of mine:

From good server:

Copied the MBR
# dd if=/dev/hda of=/tmp/hdambr bs=512 count=1

This created a backup of the MBR in /tmp/hdambr. I then copied this file over to the 'troubled' linux server. First, I attempted to restore just the MBR which is contained in the first 466 bytes:
# dd if=/root/hdambr of=/dev/md0 bs=1 count=466

Then, I tried to reboot, but it still didn't recognize the MBR. The partition table is located in bytes 467 - 510, and the last two bytes are used to mark the MBR. I'm not really sure what this is, but it's needed. So, I then tried to copy just these two bytes over:

# dd if=/root/hdambr of=/dev/md0 bs=1 count=2 skip=510

I tried rebooting, but nothing. I'm not sure if this command would have actually put the two bytes (511, 512) in the correct positions on /dev/md0. The skip portion is telling dd where to skip on input, but I'm not sure where the "of" (/dev/md0) would have written the two bytes. I then tried to copy over the entire 512 bytes of the MBR and attempted to update the partition table, but no luck. So, I then decided to re-load the OS which recognized all of the RAID partitions and LVM vols, so I decided against re-formatting them in hopes that laying down the new MBR would take care of everything. It didn't. I then reformatted both SCSI drives via the SCSI BIOS and then re-loaded the OS. Everything is working good now. (I should have formated the drives before installing the OS the first time. Lesson learned.)
Old 08-06-2005, 12:52 PM   #5
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Check the partition table. See that it is correct. Windows operating systems require the "lba" flag.

Once you reboot from your rescue disk, you can use a grub command to rewrite the master-boot-record (MBR). The message you're getting comes from the BIOS, which cannot find a bootable system. (Have you checked the BIOS settings to see where it is trying to boot from?)


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