Re: debugging grub2

[Pascal Hambourg]

Le 05/09/2018 à 08:26, daggs a écrit :
> I have a setup that runs centos installer (CentOS-7-x86_64-DVD-1804.iso) from 
> cd in uefi, thing is, when it get to grub, instead of showing the menu, I get 
> grub rescue.
> ls shows (cd0) but no partitions.

Why should it show any partitions ? A CD-ROM has no partitions.
Can ls show the contents of (cd0) ?

> I've verified the installer is ok on another system so this is not an installer 
> issue.

In UEFI mode too ?

> I want to enable debugging in grub to see if I can understand what is the issue.
> I've mounted the iso and entersed grub.cfg, there I've added this fourlines:
> set pager=1
> set debug=all
> serial --unit=0
> terminal_output serial

How did you manage to modify a file in a read-only filesystem (ISO9660) 
on a read-only medium (CD-ROM) ?

> after the first line (set default=1)
> but I still don't get any debug prints in the serial.

Of course not. grub.cfg is read in normal mode, but dropping to the 
rescue shell means that GRUB could not find the normal module and switch 
to normal mode.