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My machine is using Ubuntu 8.04 (=> legacy grub). It is backed up regularly and I would like to check I am able to restore the backup.

This backup includes everything on the system, including /boot (the only things excluded are things like /proc, /var, /dev...).

I "restored" the backup onto an external USB HDD, setup the boot flag there and I would like to boot that. Is that possible ?

I tried several variants of grub-install, changing the menu.lst, but still no luck. For one thing, the /boot/grub/device.map only shows the main HDD, not the USB HDD, is it ok to just add it in there? :

(hd1) /dev/sdb1

When I change the BIOS to boot from USB, it just seems to skip it.

What else do I need to do ?

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3 Answers 3

Have you checked grub-install ?

read http://www.linuxselfhelp.com/gnu/grub/html_chapter/grub_3.html

that should get you sorted.

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Thanks for the help... I mentioned in the question : "I tried several variants of grub-install,..." so yes, I've looked into it, but either I am not using it right or this is not the right thing... –  Matthieu May 24 '11 at 16:37
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up vote 0 down vote accepted

Eventually I got it working by using Plop Boot Manager. I got the tip on the Ubuntu forum (sorry, I don't have the link to the discussion thread here).

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Your Ubuntu machine has the boot loader on your MBR which will load your main GRUB Legacy boot manager located on the internal HDD. You have an external USB HDD, which has the other copied GRUB Legacy boot manager that you want to access.

You'll want to edit /boot/grub/menu.lst (grub.conf for fedora, rhel, etc.) since you're on Ubuntu and add a per-image option for the backup HDD. Adding to or modifying the device.map file [edited: and/or using the grub command - check up on documentation] is the correct way to identify other GRUB boot manager locations to GRUB. The parititions also need to be set bootable by fdisk. This link along with the link within it describes the use of the grub command: Linux RAID 1: How to make a secondary HD boot?

You'll have to take care to make the mounting of the external HDD make sense but that's not talking about GRUB. Obviously, backup programs have more options and are better suited for restoration of the required files.

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