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

[Tong Sun]

Thanks Gene,

On Mon, Aug 5, 2019 at 7:00 AM Gene Cumm wrote:
>
> On Sun, Aug 4, 2019 at 6:13 PM Tong Sun via Syslinux
> <syslinux at syslinux.org> wrote:
> >
> > 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
>
> Presumably this is just a file copy and not duplicating things like
> the VBR (the first sector of the file system/partition).

Exactly, only duplicate files via rsync

> > - then after the transfer, I always do a extlinux install via
> >
> >     extlinux --install $new_os_mnt/boot/extlinux
> >
> > I think this should be enough, however, the strange problem is that it
> > is not fully working:
> >
> > - its menu shows up fine but can’t boot /vmlinuz
>
> In the context of your shell command, I assume this exists as
> "$new_os_mnt/vmlinuz"?  Or did you really want to load
> "$new_os_mnt/boot/extlinux/vmlinuz" and should have specified
> "vmlinuz"?

Yes, there is "$new_os_mnt/vmlinuz"; no, there isn't a
"$new_os_mnt/boot/extlinux/vmlinuz".

> > - after sellecting the menu, it shows “Loading /vmlinuz...” then
> > flashed “failed”, and go back to the menu again.
>
> What is "$new_os_mnt/vmlinuz"?  A real file or a symlink?

A symlink

/vmlinuz -> boot/vmlinuz-4.15.0-54-generic

As stressed before,

- the same symlink & extlinux config works from the original mirroring source.
- and I can boot it with Grub4dos
- moreover, I've tried adding another extlinux menu entry that using
directly /boot/vmlinuz-4.15.0-54-generic, but it has the same symptom
as using /vmlinuz as well.

> > 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
>
> --
> -Gene