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Re: Dedicated grub2 partition

From: Goh Lip
Subject: Re: Dedicated grub2 partition
Date: Wed, 06 Oct 2010 09:36:04 +0800
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100922 Thunderbird/3.1.4

On Wednesday 06,October,2010 07:29 AM, Barry Jackson wrote:
Hi Goh,
No joy yet :-(

I have currently 4 test entries which I am now numbering to keep track :-
menuentry 'Test 1' {
   loopback loop (hd0,1)/pclinuxos-lxde-2010.1.iso
   linux (loop)/isolinux/vmlinuz findiso=/pclinuxos-lxde-2010.1.iso
boot=boot quiet  noeject noprompt
   initrd (loop)/isolinux/initrd.gz

menuentry 'Test 2' {
loopback loop (hd0,1)/pclinuxos-lxde-2010.1.iso
linux (loop)/isolinux/vmlinuz findiso=/pclinuxos-lxde-2010.1.iso
boot=live quiet noeject noprompt
initrd (loop)/isolinux/initrd.gz

menuentry 'Test 3' {
loopback loop (hd0,1)/pclinuxos-lxde-2010.1.iso
linux (loop)/isolinux/vmlinuz boot=isolinux vga=788 fromusb
root=/dev/sda1  acpi=on fstab=rw,noauto
initrd (loop)/isolinux/initrd.gz

menuentry 'Test 4' {
loopback loop (hd0,1)/pclinuxos-lxde-2010.1.iso
linux (loop)/isolinux/vmlinuz
isofrom=/dev/sda1/pclinuxos-lxde-2010.1.iso boot=live quiet noeject
initrd (loop)/isolinux/initrd.gz
Tests 1,2,and 4 all produce the same kernel panic at the start of boot
when trying to run the initrd.

Test 3 runs the initrd fine until it tries to access livecd.sqfs and
fails to find it on a real device.

Sorry about the bad photos.


Hi Barry, I was about to give up when I saw "fromusb" in the 'test 3' and that 'worked somewhat' up to the point of not finding the loop. Your fairly good pics show sda, sdb and sdc.

Your iso file is not in the usb disk, right? (you said it is in sda1 root partition). Please help me understand why the "fromusb' was added in, and if this is from the old line to boot the extracted sqsfs file, was this extracted to the usb as well?

To jump the gun if it is the usb, using (hd0,x) and /dev/sdax for booting usb and indeed other than primary hard disk is fraught with errors (by bios, not uefi). It is best to use
"search --xxxxxxxxxxxxxxxx" and avoid (hd0,x)
Also avoid using "=/dev/sdax and use.... oh boy, don't think we can use label or uuid here; that's why 'findiso' replaces 'isofrom=/dev/sdax" but the problem is sometimes 'findiso' doesn't work with some livecd's.

Let's see...we can, at grub prompt, do a
<check which is the usb entry>
say, if it is really (hd0,1), then
ls (hd0,1)
<and check if it is sda1 or sdb1 or sdc1,
then modify the 'isofrom=/dev/sdyx/ ...." to the correct y and x>

Barry, note that this might change with next boot up.
ie., usb disk may become (hd2,1) instead or /dev/sdb1

Oh, if it is not on the usb, and the usb and external drives are not required, lets, pull out all these disks so that it doesn't mess up the boot.

Seriously, Barry, I was about to give up. Have been raking my brains out. Nowadays, I only boot up iso (casper) for those 'pre-release' OS to test out and had been installing even those "alpha 3's" (by then, fairly okay) to disk. - reason being kernel changes cannot be made persistent- (there are ways, but too complicated to bother with). And grml, rescuecd, gparted, grubcd is made obsolete by my "lubuntu-on-the-stick".

Regards - Goh Lip

ps; like your tenacity  :)

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