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Thread: Hard disk backup : confusions, still !!!

  1. #1
    nusjunkie
    Guest

    Hard disk backup : confusions, still !!!

    I have 2 hard disks in my server. Initially I installed Linux only on hda, whereas hdb was left unformatted. I just formatted hdb, created appropriate partitions and using 'dd' command, I backed up all my data(EVERYTHING from hda) into hdb.
    A few questions related to this :
    1) If I am working on hda and hdb is unmounted, in case of a harddisk failure, hdb will be unaffected. Am I right ?
    2) If hda crashes, can i boot from hdb ?

    Any other information about this type of backing-up procedure shall be highly appreciated.
    Thank you guys !!!

  2. #2
    Aaron_Adams
    Guest

    Re:Hard disk backup : confusions, still !!!

    If hdb is unmounted, and a crash happens on hda, it won't effect hdb at all.

    If you have a boot image on hdb, which I assume you do as it is basically a mirror of hda, then you should be able to fine. It should be as much as adding

    image=<image path here>
    root=/dev/hdb*
    label=Linux on hdb ( or whatever )

    to your /etc/lilo.conf
    don't forget to run '$/sbin/lilo' afterwards

  3. #3
    JimH
    Guest

    Re:Hard disk backup : confusions, still !!!

    Quote Originally Posted by nusjunkie
    A few questions related to this :
    1) If I am working on hda and hdb is unmounted, in case of a harddisk failure, hdb will be unaffected. Am I right ?
    Correct.

    2) If hda crashes, can i boot from hdb ?
    Yes, but it might require some extra work.

    If you have an exact copy of the drive, with dd you should, you can just unplug the original hda and replace it with hdb and reboot. If the bootloader was copied everything will work fine.

    If the bootloader wasn't copied you should be able to use CD 1 of your Linux distro as a rescue disk. You can boot with it reinstall the bootloader and everything should work.

    However, this should not be a problem using dd.

    What Linux distribution are you using? What bootloader are you using, lilo or grub?

    Jim H

  4. #4
    nusjunkie
    Guest

    Re:Hard disk backup : confusions, still !!!

    Hi Jim...
    I'm using Red Hat 7.2 with GRUB as the bootloader.
    Could u pls explain the process in a bit detail i'm a total newbie :-\

    Thanks a lot...

  5. #5
    JimH
    Guest

    Re:Hard disk backup : confusions, still !!!

    After you switch hdb to hda and you reboot, but the grub boot screen doesn't appear you can use CD 1 to restore the bootloader.

    Put CD 1 into the cdrom drive.
    Reboot the computer.
    The linux boot prompt will appear, just like when you first installed linux.
    At the boot prompt type: linux rescue

    The kernel will boot from the cd, you will be asked a couple questions, language and keyboard. It will finish booting and it should tell you that your system was mounted under /mnt/sysimage.

    To restore the grub bootloader type:

    chroot /mnt/sysimage

    grub-install /dev/hda

    That will restore the grub bootloader.
    To reboot type: exit
    This will exit the chroot environment.
    Then type exit again to reboot the computer. Don't forgot to remove the CD from the drive. You should see the grub boot screen come up and you can boot normally.

    I would recommend that when you can take your server down that you test this and make sure your backup on hdb is good. I would not wait until something happens to find out your backup procedures don't work.

    Jim H

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