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Re: How to usb boot from Grub2 in Cdrom

From: Jordan Uggla
Subject: Re: How to usb boot from Grub2 in Cdrom
Date: Mon, 19 Mar 2012 04:22:52 -0700

On Mon, Mar 19, 2012 at 3:33 AM,  <address@hidden> wrote:
> I use a Computer which cannot boot from usb memory.
> I would like to boot usb memory with Grub2 in CD-RW.
> I entered following commands.
> insmod uhci
> Then usb memory was detected with (usb0).
> I checked it with ls command.
> Then I would like to boot with chainloader.
> set root=(usb0)
> chainloader +1

Chainloading cannot be used when using grub's native USB drivers
because grub does not add int13 hooks to allow other bootloaders to
access USB devices as well. If you want to boot from a USB drive using
grub's native USB drivers you need to load the kernel / initrd

> But I got following error message.
> Hard Disk Error
> Insert system disk in drive.
> Press any key when ready....
> I can boot the usb memory with  "Plop Boot Manager".
> I would like to boot with Grub2 without Plop Boot Manager.
> (The usb memory was installed Ubuntu Linux. That can boot. I checked it with 
> qemu.)

Since the USB drive contains an Ubuntu install, and Ubuntu uses grub2,
you can simply load Ubuntu's grub.cfg rather than using chainloading:

configfile /boot/grub/grub.cfg

Though ideally "root=(usb0,msdos1)" should be replaced with "search
--set=root --fs-uuid UUID_HERE" so that the entry will continue to
work even if you plug in other USB drives and change drive

Also, I don't know if you noticed but you posted your question to the
list twice. Please don't do that.

Jordan Uggla (Jordan_U on

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