Re: Idea: Improve ext2 to allow for embedding

[Dr. Tilmann Bubeck]

Yes, thats exactly the use case: I always have multiple linux 
installations (ubuntu and fedora) in two seperate partitions. To stay 
compatible with their individual kernel and grub updates, I always 
install a second GRUB into the root parition of the specific linux 
installation. In MBR I have a master GRUB to select the linux system 
(partition) to chainload the second GRUB of that distribution. For this 
use case I need GRUB to be installed into ext4 of the root partition of 
that linux system.

On 13/03/2024 at 11:25, Mate Kukri wrote:

> >    Do you have a proposed use-case for this in mind?
> >    On MBR disks there is usually enough space for core.img before the
> >    first partition.
> >    On GPT you can simply create a so-called "BIOS boot partition" to
> >    store core.img.

> A use case could be when you do not want to install the GRUB boot image 
> in the disk MBR as the primary boot loader but in a partition boot 
> sector as a secondary boot loader.


    On Wed, Mar 13, 2024 at 10:22 AM Dr. Tilmann Bubeck 
<tilmann@bubecks.de> wrote:


        I would like to propose a change to GRUB to allow embedding 
(fs_embed)
        of core.img for ext2/3/4 into the
        filesystem. This allows the installation of GRUB into ext2 
without the
        need to use (unsafe) block lists.

        It will be realized using the ioctl(EXT4_IOC_SWAP_BOOT) 
introduced into
        Linux 3.10 in 2013. This ioctl basically swaps the data blocks 
of the
        associated file with the EXT2_BOOT_LOADER_INO inode. After using 
the
        ioctl the code of core.img is stored in the BOOT_LOADER incode 
of the
        filesystem and it is not accessible to file system tools 
anymore. This
        ensures, that the boot code is safe and installation into a 
partition is
        possible.

        What would you think about this proposal. Are you willing to 
integrate
        this, if I develop this for GRUB?

        Changes will be done mainly in setup.c and ext2.c