I've found the solution :)
First of all: what change in initramfs? Only the kernel modules, So I did this
I have copied the original image of debian netinstall in a Debian vm (ppc64 with custom kernel)
mkdir temporary cp original-initrdfromdebianportcd.gz . gzip -d original...
extract it
unmkinitramfs -v original .
Now, we need the original modules? No, we need custom modules (extract the initramfs custom image with unmkinitramfs as we did for original in another directory)
pwd #just to avoid to delete something important rm -fr 6.1.0-9-powerpc64/ cp -av modulesfromcustominitramfs .
in my case
mv -v ../directorywithcustomiinitramfswhichdont'workbefore/5.15.164/ lib/modules
Now we have to rebuild initrd
find . | cpio -ov -H newc| gzip -c >/boot/initrd.new.img
We transfer it to directory of iso extracted in folder install
in this folder we have two files
initrd.gz vmlinux
so
cp /boot/initrd.new.img initrd.gz
We rebuild the iso!
xorriso -as mkisofs -r -V 'Debian 12 Rescue ppc64' -o debian-12.0.0-ppc64-Rescue-2.iso -J -joliet-long -cache-inodes -chrp-boot-part directorywhereyouextractfiles
testing with qemu-ppc-64 works really fine :) Don't care about image corruption
Let's see the custom kernel
BusyBox v1.35.0 (Debian 1:1.35.0-4+b3) built-in shell (ash) Enter 'help' for a list of built-in commands. ~ # uname -r 5.15.164 ~ #
Very good! It will also possible to extend cd with new packages but is another story. On qemu-ppc64 works, will be work also in 9111-285? I will try asap (tried and works, only some fix, for example the cd must be mounted from shell (probaly because the 9111-285 has 2 cdrom drive).
