regression: ks.cfg can't be fetched from writable partition of installation media (ESP)

[bam80]

Fedora's .ISO installer images also contain appended vfat EFI System Partition (ESP) in it.
The boot.iso typically has the following structure:

    NAME   TYPE  SIZE FSTYPE  LABEL
    sda    disk  8.8G iso9660 RHEL-8-3-0-BaseOS-x86_64
    |-sda1 part  8.8G iso9660 RHEL-8-3-0-BaseOS-x86_64
    `-sda2 part   10M vfat    ANACONDA

The problem is, that sda2 vfat ANACONDA partition can never be mounted by Anaconda installer, as the whole sda disk is mounted as rootfs first.

This is regression introduced by https://pagure.io/centos-sig-hyperscale/anaconda/c/301a09d06ee0f0df7a3a1c818d7051f31a12bbd1?branch=4532ca0cb394c5ed0eb3b99865adff9b98d6adb7
301a09d "Never mount partitions on a disk with the iso9660 filesystem (#1878784)"

I deem it quite severe as that vfat EFS was the only handy place for custom Kickstart ks.cfg file, if user flashes the .ISO to SD card or USB drive.

More details:
https://bugzilla.redhat.com/show_bug.cgi?id=2346192
Fix proposed:
#6222

@poncovka

[bam80]

Alternative solution to the problem described in the guilty patch but without triggering the bug is to use partition LABEL (PARTLABEL) in the installer's grub.cfg file instead of filesystem LABEL,
so inst.stage2 option in the <ESP>/EFI/BOOT/grub.cfg file should be changed accordingly:

• original menu-entries linuxefi command with filesystem LABEL, e.g.:
  linuxefi /images/pxeboot/vmlinuz inst.stage2=hd:LABEL=Fedora-SB-ostree-x86_64-41
• changed entry with symlink name pointing to the device by partition LABEL instead:
  linuxefi /images/pxeboot/vmlinuz inst.stage2=hd:/dev/disk/by-partlabel/ISO9660

The various labels and UUID's used in the installation image can be seen as here:

# setup loopback device and partitions within
$ sudo losetup /dev/loop0 --partscan Fedora-Silverblue-ostree-x86_64-41-1.4.iso

# output properties of the block devices
$ lsblk /dev/loop0 -o NAME,UUID,LABEL,PARTLABEL
NAME      UUID                                 LABEL                      PARTLABEL
loop0     2024-10-24-14-37-30-00               Fedora-SB-ostree-x86_64-41 
├─loop0p1 2024-10-24-14-37-30-00               Fedora-SB-ostree-x86_64-41 ISO9660
└─loop0p2 BA81-F12E                            ANACONDA                   Appended2