[syslinux] Problem with cascading configurations

[Malte Forkel]

Am 06.09.2019 um 06:28 schrieb Ady Ady via Syslinux:
>> Relocating ldlinux.c32 as you suggested didn't have any visible effect
>> on the boot process. Error message and TFTP log entries are the same.
>  
>  
> Adding ldlinux.c32 to the location where pxelinux.0 is located is only 
> one part of the troubleshooting process. The addition to the "right" 
> location might change the initial "working directory" (when comparing 
> to the prior situation, originated/based on the netboot images' parent 
> tree). This change might (or might not) be useful.
>
> As I said in my prior email, the aforementioned addition/change cannot 
> really resolve the (potential) conflict between Syslinux's versions.

The relocation proofed to be not necessary when pxechn.c32 was used (see
below).

> One possible workaround for the versioning conflict (that might work in 
> some cases) would be to use pxechn.c32 (from the same version as the 
> active pxelinux.0 bootloader) instead of your CONFIG directive entries.
>
> With CONFIG, the cfg files are (expected to be) parsed by the same 
> version of Syslinux. Using pxechn.c32 instead, you first chainload the 
> pxelinux.0 file/version that comes within the respective netboot.img.gz 
> archive. From that point on, the "new" pxelinux.0 expects its 
> corresponding ldlinux.c32 and all c32 modules that are already included 
> within the same netboot image. As long as the Syslinux's binaries work 
> correctly, the versioning conflict should no longer be a problem.
>
> There are several places to look up for info about pxechn.c32, 
> including the Syslinux wiki.
>
>
Thanks, using pxechn.c32 solved my problem. The sample configuration now
looks like this:

    LABEL Debian_9_i386
        MENU LABEL Debian 9 Stretch Network Installer (i386)
        KERNEL pxechn.c32 debian/stretch/pxelinux.0

    LABEL Debian_10_i386
        MENU LABEL Debian 10 Buster Network Installer (i386)
        KERNEL pxechn.c32 debian/buster/pxelinux.0

I had top copy pxechn.c32 and libcom32.c32 to directory syslinux in the
TFTP server's root.

Regards,
Matle