Re: Debug grub scripts without rebooting into grub shell.

[Andrei Borzenkov]

On 09.07.2023 03:21, Hongyi Zhao wrote:
> On Sat, Jul 8, 2023 at 9:53 PM Andrei Borzenkov <arvidjaar@gmail.com> wrote:
> > On 08.07.2023 14:58, Hongyi Zhao wrote:
> > > Hi here,
> > >
> > > Are there some convenient methods to debug grub scripts without
> > > rebooting into grub shell?
> >
> > You may try grub-emu which emulates grub.
>
> I tried, but it seems that grub-emu doesn't meet my requirement as
> described below.
>
> I want to debug the grubx64.efi created by the following command:

If you want to debug grubx64.efi, then you of course need to load it 
either on real hardware or in VM. But you can debug scripts used by 
grubx64.efi using grub-emu by setting up suitable simulated environment. 
There are clear limitations (scripts cannot load and start any kernel).

> $ grub-mkstandalone -O x86_64-efi -o grubx64.efi --modules='lvm fat
> ntfs part_msdos part_gpt ext2 btrfs probe regexp search configfile'
> boot/grub/grub.cfg=./grub.cfg
>
> The content of the ./grub.cfg is as follows:
>
> $ egrep -v '^[ ]*(#|$)' grub.cfg
> regexp -s __cmdpath_efi '^\(([^,]+)' "$cmdpath"
> export __cmdpath_efi
> for file in ($__cmdpath_efi,*)/multibootusb.git/grub.cfg; do
>    if regexp -s __root '^(\([^*]+\))' "$file"; then
>      set __prefix=$__root/multibootusb.git
>      export __root
>      export __prefix
>      configfile $__prefix/grub.cfg
>      break
>    fi
> done
>
> The files' layout is as follows:
>
> $ tree .
> .
> ├── grub.cfg
> ├── grub-mkstandalone.sh
> ├── grubx64.efi
> └── iso
>      ├── deepin-desktop-community-23-Beta-amd64.iso
>      ├── rescatux-0.74.iso
>      ├── supergrub2-2.06s1-beta2-multiarch-CD.iso
>      ├── systemrescue-10.01-amd64.iso
>      ├── ubuntu-23.04-desktop-amd64.iso
>      └── ubuntukylin-23.04-desktop-amd64.iso
>
> 1 directory, 9 files
>
> Regards,
> Zhao