#3520 PR open: Remove support for outdated syslinux (<4.04) and simplify the ISOLINUX config generator

Labels: cleanup

lzaoral opened issue at 2025-09-13 06:30:

Pull Request Details:

  • Type: Clean-up

  • Impact: Normal

  • How was this pull request tested? Boot of OUTPUT=ISO in RHEL 7-10 and Fedora Rawhide.

  • Description of the changes in this pull request:

    • drop support for syslinux <4.04 because 4.04 is the oldest release in distros supported by ReaR 2.9, see https://repology.org/project/syslinux/versions for details.
    • fix detection of memtest86 for isolinux on RHEL and Fedora
    • simplify the isolinux config generator

The plan is to merge the PXELINUX and EXTLINUX generators into lib/bootloader-functions.sh in subsequent pull requests as well.

At the moment, HDT entry is not bootable on RHEL8+ and Fedora but that is an issue not caused by these changes and is tracked in https://issues.redhat.com/browse/RHEL-114110.

(Note that I've used Claude Code to detect relevant code to be removed/changed. However, all edits and commits were done solely by me.)

lzaoral commented at 2025-09-26 08:48:

I'm going to mark this PR as a draft because I'll probably have to make some minor changes to it as I progress with the extlinux and pxelinux merge locally. Nonetheless, even if this is a draft, reviews are welcome!

jsmeix commented at 2025-11-12 13:55:

@lzaoral
I had only a quick first view.

From your changes in usr/share/rear/conf/default.conf
it seems you changed the meaning of ISO_DEFAULT
(it seems you removed ISO_DEFAULT completely)
and merged it into ISO_RECOVER_MODE.

But - as far as I see - there is no code which handles
when the user has set ISO_DEFAULT
e.g. after an upgrade from older ReaR to ReaR 3.0.

I think for a ReaR major version upgrade
backward compatibility is not required
so no code is needed which automatically maps
old ISO_DEFAULT values into new ISO_RECOVER_MODE.

But I think it should at least Error out when ISO_DEFAULT
is set in a way which is known to be no longer supported
so the user is informed that his ISO_DEFAULT setting
is no longer supported, cf.
https://github.com/rear/rear/blob/rear-2.9/usr/share/rear/prep/default/020_translate_url.sh#L25
and its reason behind
https://github.com/rear/rear/pull/2011#issuecomment-452723383

[Export of Github issue for rear/rear.]