boot problem with cloned hard drives

stevebrooks452 · 03-21-2006, 02:41 PM

Hi Everyone,

(My first post)

I am running a NIS/NFS file server for a small maths dept. The OS (FC4) and all the users home areas are on the same 120G sata HD "sda" on different partitions. I made an exact clone of the first hard drive (sda) onto a new drive (sdb) and it worked fine. That is I can now boot from either drive sda or sdb when only that drive is plugged into the port "SATA1" on the motherboard and the second port "SATA2" is not connected. My plan was to run the system from the main drive "sda" and simply mount the partition with the users home areas from the second drive "sda2" and "rsync" the changes every night.

The problem is when I try to boot with both dives connected the system actually seems to try to boot from both drives. I had assumed that making only the "sda" drive bootable in the BIOS would prevent this from happening. Do I need to work out how to configure GRUB to only boot from the drive "sda"?

Any help would be much appreciated.

Thanks,

Steve

Lenard · 03-21-2006, 03:28 PM

Red Hat / Fedora makes use of partition labels, not a good idea with cloned drives on the same system. Both drives have the exact same named partition label(s) and confusion happens, you need to change these labels on one of the hard drives, read; man e2label

stevebrooks452 · 03-21-2006, 03:43 PM

Lenard - thanks for your replay I will try this tomorrow.

Steve

Lenard · 03-22-2006, 06:22 AM

Forgot to tell you that you can just not use them at all. This requires editing both /boot/grub/grub.conf and /etc/fstab, examples below;

First grub;

Code:

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,2)
#          kernel /vmlinuz-version ro root=/dev/hda5
#          initrd /initrd-version.img
#boot=/dev/hda
default=0
timeout=15
splashimage=(hd0,2)/grub/splash.xpm.gz
hiddenmenu
title CentOS (2.6.16)
        root (hd0,2)
        kernel /vmlinuz-2.6.16 ro root=LABEL=/ quiet vga=791 npapic

Grub is nice an offers a clue in the top comment section, following the clue the kernel line changes from;

kernel /vmlinuz-2.6.16 ro root=LABEL=/ quiet vga=791 npapic

to;

kernel /vmlinuz-2.6.16 ro root=/dev/hda5 quiet vga=791 npapic

Editing /etc/fstab is a bit harder, you have to know or find out which partition label is which actual device/partition. You already had one given to you from grub.conf and many times you have clues in the file. Just taking the root partition as an example (the easy one of course);

Code:

# This file is edited by fstab-sync - see 'man fstab-sync' for details
LABEL=/                 /                       ext3    defaults        1 1

is changed to;

Code:

# This file is edited by fstab-sync - see 'man fstab-sync' for details
/dev/hda5                 /                       ext3    defaults        1 1

It is not hard but does take a small bit of effort, no more effort then to change the labels with e2label or tune2fs -L (another way to edit the labels).

For LVM volumes see;
http://www.redhat.com/docs/manuals/e...orage-lvm.html

stevebrooks452 · 03-23-2006, 03:07 AM

Lenard,

Thanks for the help, changing the labels with "e2label" and changing the "grub.conf" and "fstab" did the trick. I can now mount the requred partitions from the seconary drive "sdb" and "rsync" appropriately to keep the required partitions cloned.

I guess this is really just a poor mans solution to RAID1 - however it has the advantage of avoiding third party raid drivers that I have found not reliable enough yet.

Thanks Again

steve