Re: Grub Troubleshooting

[wangji]

John Lewis <address@hidden> writes:

> 
> Is there a more efficient way to troubleshoot GRUB issues. Right now I
> am in a nearly blind, change grub.cfg and boot. If there is an issue
> with the initramfs  I am completely blind to how to fix that. Here is a
> thread of me trying to resolve a a problem with booting a Debian DVD
> with GRUB
>
>
> http://forums.debian.net/viewtopic.php?f=17&t=127701.
> &sid=8bdd5085a64e7756717cdc1887d7c67a.
> from this debianforum link,you wrote:
> set imgdevpath="/dev/disk/by-label/multiboot"
>
> Code: Select all
>    menuentry 'Debian Jessie amd64' {
>            set isofile='/iso/debian-8.0.0-amd64-DVD-1.iso'
>            loopback loop $isofile
>            linux (loop)/install.amd/vmlinuz
>            initrd (loop)/install.amd/initrd.gz
>    }

grub environment is totally independent of linux's
env-kernel_initramfs_world- all you can do is to hand over 
some parameters['s locations].
On real machine once grub gets into your grub's menu it needs to have the
right $root (eventually $prefix).

The imgdevpath is in nix's world,so your emulator can get grasp of it,but
not grub !!!!

On bare metal your grub's menu needs surely something of the kinds  
 
"search -f -s $isofile"          before the loopback line. 

As demo of multiboot of linuxaio-fedora23-amd64.iso which only boots in
legacy CSM mode.A correct grub.cfg is enough to make it boot on uefi_pc
using any current grub2-efi stick .
see:
https://sourceforge.net/projects/toysbox/files/linuxaio-fedora23-amd64 Put a
tiger grub on it/