[syslinux] Extlinux no longer bootable, how to fix?

[Tong Sun]

Hi,

I'm experiencing a strange problem, my extlinux is no longer bootable,
and I'm wondering how to troubleshoot the problem for a fix.

It's not just an one-off thing, but is happening to me all the time --
I use extlinux to boot up all my linux, and it has always been working
for me, for at least 10+ years. However recently I started to
duplicate my linux system from partition to partition, from a
carefully configured one, and from machine to machine as well.

- during the mirror/transfer, I always exclude the
/boot/extlinux/ldlinux.sys file
- then after the transfer, I always do a extlinux install via

    extlinux --install $new_os_mnt/boot/extlinux

I think this should be enough, however, the strange problem is that it
is not fully working:

- its menu shows up fine but can’t boot /vmlinuz
- after sellecting the menu, it shows “Loading /vmlinuz...” then
flashed “failed”, and go back to the menu again.

Here is my extlinux menu:

LABEL LU18R1
        MENU LABEL LUbuntu ^Bionic
        MENU DEFAULT
        KERNEL /vmlinuz
        APPEND initrd=/initrd.img
root=UUID=ad26a5d8-a4ee-42d3-96aa-1f6f0eaa3968 ro net.ifnames=0 --

- the same extlinux config works from the original mirroring source.
- I've made sure the UUID is updated, thought I think it is irrelevant
as it is the loading of /vmlinuz failed.
- I.e., the real problem is loading the /vmlinuz from extlinux

To confirm the situation, I've duplicate my linux system to at least
three HD partitions, and none of them works. However, using the
exactly same steps, when duplicate to my USB key, the system boots up
beautifully. That's why I'm saying that it is a strange problem.

If you are curious how I boot different linux from different partitions,

- I have extlinux booted from the active partition,
- then chain loading into different linux partitions
- the linux system from the mirrored partitions boot up fine, as I can
start them from Grub4dos. Moreover,
- I Install & boot from grub2, and it is OK too. But I really don't
like grub2, and would like to make extlinux work instead.

All in all, the only problem is loading the /vmlinuz from extlinux, as
the chainloading is fine, and the linux system itself boots up fine
too. and I'm wondering how to troubleshoot the problem, and the fix
too.

Thanks