Re: Booting an ISO file from GRUB

[Andrei Borzenkov]

On 14.02.2024 11:26, Marko Toivanen wrote:
> I have been trying to find information related to the following problem:
>
> I'm trying to start a Lubuntu 22.04 installation from an older Lubuntu
> 14.04 installation by booting the ISO file from grub menu.
>
> Booting the ISO file works by adding the following menu configuration to
> file /etc/grub.d/40_custom:
>
> menuentry "Linux ISO to RAM" {
>       insmod lvm
>       insmod ext2
>       set root="lvm/lubuntu--vg-root"
>       set isofile="/home/user/lubuntu-22.04.3-desktop-amd64.iso"
>       loopback loop $isofile
>       linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile
> toram
>       initrd (loop)/casper/initrd
> }
>
> The problem is when Lubuntu 22.04 starts this way, there is a device
> "/dev/lubuntu-vg" showing up in Linux (what I didn't expect) and because

Well, installer needs to read a file from the filesystem on the logical 
volume so it needs to configure this logical volume. What miracle did 
you expect?

> of that, I can't make a clean install of Lubuntu 22.04 on the hard drive
> when Lubuntu was started from the ISO file (which is located on the hard
> drive).
>
> My initial thought was that using "toram" option would completely load
> the ISO to RAM, so I could then be able to repartition the hard drive
> without having to start Lubuntu 22.04 installation from an USB stick.
>
> When I try to repartition /dev/sda (where this lubuntu-vg is located)
> with gparted, I get the following error message:
>
> "we have been unable to inform the kernel of the change, probably
> because if/they are in use"
>
> So, is it possible to boot an ISO file so the problem described wouldn't
> happen?

It is completely unrelated to grub. Once kernel starts, grub is not in 
charge anymore. Apparently your installer does not deactivate LV/VG 
after reading ISO, but that is something you need to raise up with your 
distribution.