[syslinux] Is Syslinux still in active development?

[Thomas Schmitt]

Hi,

Turritopsis Dohrnii Teo En Ming wrote:
> I found that Syslinux is being used in many Linux distro ISO
> installers.

The community of distro ISO producers is very slow with adopting new
things while the old stuff still works.

This is solidified by experience, e.g. the fact that switching away from
the ISO boot equipment and partition layout of Matthew J. Garret's
BIOS,EFI x DVD,USB-Stick ISOs always leaves behind some old machines or
odd EFI implementations. Sometimes because GRUB2's BIOS-related software
does not work well with a particular firmware implementation, sometimes
because firmware has particular non-standard expectations towards the
partitioning.

But the inactivity of the SYSLINUX project and its lack of support for
booting via EFI from CD/DVD/BD made GRUB2 necessary for about any distro.
I.e. the configuration files had to be translated from SYSLINUX to GRUB2
already.
So from the view of distro ISO producers it makes sense to use GRUB2 for
both, PC-BIOS and EFI. Further, they get support requests for adding
partitions to USB sticks with their ISOs, which means that they need to
clean up the partition tables in the ISOs and thus necessarily already
lose most of the victims of a switch to a pure GRUB2-bootable ISO.

Afterwards it's not much of a risk to give up the use of ISOLINUX.


Frantisek Rysanek wrote:
> The alternative [to ISOLINUX] would probably be the "floppy
> emulation boot" = an even older style, allowing you to load the
> kernel in yet other ways... Isolinux uses the so-called "no-emulation
> boot", which once was the progressive way (two decades ago?) and is
> probably the most popular bootloader with that capability.

GRUB2 provides a no-emulation boot image for El Torito which is equivalent
to isolinux.bin . Similarly to isolinux it needs some help from the ISO
producing program (see -boot-info-table in man mkisofs/genisoimage/xorrisofs
and --grub2-boot-info in man xorrisofs).

There is also a piece of MBR code, equivalent to isohdpfx.bin of ISOLINUX,
which lets PC-BIOS hop onto the El Torito boot image if the ISO is presented
on a USB stick.

No-emulation is the only non-legacy mode of El Torito. The others emulate
booting by images of a floppy (1200 1200 KiB, 1440 KiB, 2880 KiB) or a
hard-disk (size given by its MBR partition table) which are stored on a
CD-ROM.


> UEFI has fought hard to take over the rule, and has managed that a
> few years ago in the office and in the datacenter,

But SeaBIOS still seems to rule parts of the world of virtual machines in
datacenters. At least i witnessed some backtalk when producers of
installation ISOs brought up the idea to give up BIOS completely.


> Apparently, other bootloaders were quicker to pick up that UEFI
> gauntlet.

SYSLINUX EFI software seems to work well from hard disk and USB stick.
But its inaptness with optical media led to the rise of GRUB2 for ISOs
and now drives out many of the remaining ISOLINUX usages.


> The CD/DVD/ISO is nowadays legacy technology

Yes. I was told this when i started to work on that topic in 2006.


> Does anyone still burn CD's nowadays?

Me. One CD-RW every 8 days. It's hard to find a backup job which fits
into 700 MiB. Mine logs DVD or BD backups which happen every second day.


> I tend to observe people flashing
> ISO9660 images onto USB thumb drives, which feels to me like fitting
> a square peg into a circular hole.

Not necesarily. The potato shape of contemporary distro ISOs comes from
the quirks of old and new firmware. It is perfectly possible to make
a circular ISO. Fedora decided to do so with its version 37.
(There was also talk to give up ISO 9660 in favor of disk filesystems, but
this did not yield changes yet.)

But, as described above, any change in the first stage of the boot equipment
risks problem with legacy hardware and oddly programmed newcomers.
(I suspect that newcomers test their firmware with existing ISOs and so
train it to stick with their potato properties.)

Then there is the fact that ISO 9660 is essentially read-only, especially to
the noobs who elsewise fiddle with anything they can change.
Together with the movement towards neater partition tables this has appeal
for the distro ISO producers.


Have a nice day :)

Thomas