[syslinux] Booting FreeBSD

Daniel O'Connor doconnor at gsoft.com.au
Wed Jul 31 04:36:19 PDT 2013

I am trying to create a hybrid ISO image for FreeBSD 9.2 using syslinux 6.01 and isohybrid.pl I found at http://www.overclockix.com/sources/isohybrid.pl (I know there is a C version in syslinux but I haven't been able to build it yet due to the UUID library being different to the one in FreeBSD).

According to the wiki mboot.c32 can boot FreeBSD, however I haven't been able to get it working. I have the following..
root at build92:~ # ll /tmp/iso/isolinux/
total 356
-r--r--r--  1 root  wheel    1185 Jul 31 01:55 cdboot.bin
-rw-r--r--  1 root  wheel   38912 Jul 31 08:17 isolinux.bin
-rw-r--r--  1 root  wheel      78 Jul 31 11:34 isolinux.cfg
-rwxr-xr-x  1 root  wheel  115472 Jul 31 01:39 ldlinux.c32*
-rwxr-xr-x  1 root  wheel  182520 Jul 31 08:17 libcom32.c32*
-rwxr-xr-x  1 root  wheel   10056 Jul 31 08:12 mboot.c32*

And syslinux.cfg contains..
  KERNEL mboot.c32
  APPEND /boot/kernel/kernel

I create the ISO with..
mkisofs -JR -o /tmp/test.iso -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -V FREEBSD_INSTALL /usr/obj/usr/src/release/bootonly /tmp/iso/

(/usr/obj/usr/src/release/bootonly is created by make release in FreeBSD)

Syslinux loads & runs fine (indeed I can use it to run cdboot.bin and that actually runs FreeBSD if I am on a CD but it does not grok HD booting) however mboot does not like /boot/kernel/kernel. I get..
"Invalid Multiboot image: neither ELF header nor a.out kludge found"

I also tried running the loader (/boot/loader) but I get the same message.

I am not really sure how I go about getting more debugging information so any ideas gratefully received :)

I am pretty sure I could fall back to using memdisk (I have used it to boot FreeBSD from syslinux in the past) but it makes the build process more complex (and this way is neater :)


Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C

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