Thomas Schmitt
2012-Jun-22 13:02 UTC
[syslinux] How to recognize an MBR suitable for isohybrid --mac ?
Hi,
i have implemented in xorriso the equivalents of isohybrid.c options --mac
and --uefi. There remains the question how to ensure that the submitted
MBR is prepared for the 32 byte mock-up of an APM Block0.
I see in git of may 2012 that all mbr/isohdp[fp]x*.bin begin by
33 ed 90 90 90 90 90 90 90 90 90 90 90 90 90 90
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90
Can i safely refuse on MBR templates which do not bear that signature
without inflicting injustice on future isohybrid MBRs ?
(I will also accept the substituted bytes of isohybrid --mac:
45 52 08 00 00 00 90 90 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
)
----------------------------------------------------------------------
I tested my implementation by re-packing Fedora-LiveCD.iso and booting
it by PC-BIOS from CD and USB stick.
I do not have hardware that would boot via APM or GPT (i.e. Mac from
CD and USB stick or hard disk). A test would be needed, because xorriso
deviates from several suspicious address computations of isohybrid.c,
and from its GPT partition names.
For the reasons of deviation see
http://www.syslinux.org/archives/2012-May/017518.html
So just in case somebody is curious, here is a description how to prepare
test media on Linux. It will need about 1.4 GB of disk space.
- Download ISO (650 MB) and the most recent xorriso development snapshot
(2.2 MB) into an elsewise disposable directory
wget http://mjg59.fedorapeople.org/Fedora-LiveCD.iso
wget http://www.gnu.org/software/xorriso/xorriso-1.2.3.tar.gz
- Build xorriso
tar xzf xorriso-1.2.3.tar.gz
( cd xorriso-1.2.3 && ./configure && make )
- Copy the MBR out of Fedora-LiveCD.iso
dd if=Fedora-LiveCD.iso bs=512 count=1 of=Fedora-LiveCD.mbr
- Mount Fedora-LiveCD.iso
mount -o loop Fedora-LiveCD.iso /mnt
- Create new ISO image FedoraRepack.iso
xorriso-1.2.3/xorriso/xorriso -as mkisofs \
-o FedoraRepack.iso -no-pad \
-isohybrid-mbr Fedora-LiveCD.mbr \
-c /isolinux/boot.cat \
-b /isolinux/isolinux.bin -no-emul-boot \
-boot-load-size 4 -boot-info-table \
-eltorito-alt-boot \
-e /isolinux/efiboot.img -no-emul-boot \
-isohybrid-gpt-basdat -isohybrid-apm-hfsplus \
-eltorito-alt-boot \
-e /isolinux/macboot.img -no-emul-boot \
-isohybrid-gpt-hfsplus -isohybrid-apm-hfsplus \
-V Fedora-LiveCD \
/mnt
(My apologies for using the unchanged Volume Id "Fedora-LiveCD".
The booting system wants to see this in its /dev/disk/by-label/.)
- Put on CD, DVD or BD:
xorriso-1.2.3/xorriso/xorriso -as cdrecord \
dev=/dev/sr0 -v blank=as_needed -eject FedoraRepack.iso
- Put on USB stick (Caution: Make sure not to overwrite your hard disk !):
dd if=FedoraRepack.iso bs=4M of=/dev/sdc ; sync
----------------------------------------------------------------------
Have a nice day :)
Thomas
Bernd Blaauw
2012-Jun-22 18:17 UTC
[syslinux] How to recognize an MBR suitable for isohybrid --mac ?
Op 22-6-2012 15:02, Thomas Schmitt schreef:> So just in case somebody is curious, here is a description how to prepare > test media on Linux. It will need about 1.4 GB of disk space.Would it be possible to create such a concept isohybrid ISO that's slightly smaller, like http://boot.ipxe.org/ipxe.iso ? That's currently 1 MB (500KB base + filler). My apologies for not being any help on your original question, maybe Matthew Garrett has some additional advice.
H. Peter Anvin
2012-Jun-24 15:00 UTC
[syslinux] How to recognize an MBR suitable for isohybrid --mac ?
Hi Matt, Do you have any input on this? -hpa On 06/22/2012 06:02 AM, Thomas Schmitt wrote:> Hi, > > i have implemented in xorriso the equivalents of isohybrid.c options --mac > and --uefi. There remains the question how to ensure that the submitted > MBR is prepared for the 32 byte mock-up of an APM Block0. > > I see in git of may 2012 that all mbr/isohdp[fp]x*.bin begin by > 33 ed 90 90 90 90 90 90 90 90 90 90 90 90 90 90 > 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 > > Can i safely refuse on MBR templates which do not bear that signature > without inflicting injustice on future isohybrid MBRs ? > > (I will also accept the substituted bytes of isohybrid --mac: > 45 52 08 00 00 00 90 90 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > ) > > ---------------------------------------------------------------------- > > I tested my implementation by re-packing Fedora-LiveCD.iso and booting > it by PC-BIOS from CD and USB stick. > > I do not have hardware that would boot via APM or GPT (i.e. Mac from > CD and USB stick or hard disk). A test would be needed, because xorriso > deviates from several suspicious address computations of isohybrid.c, > and from its GPT partition names. > For the reasons of deviation see > http://www.syslinux.org/archives/2012-May/017518.html > > > So just in case somebody is curious, here is a description how to prepare > test media on Linux. It will need about 1.4 GB of disk space. > > - Download ISO (650 MB) and the most recent xorriso development snapshot > (2.2 MB) into an elsewise disposable directory > wget http://mjg59.fedorapeople.org/Fedora-LiveCD.iso > wget http://www.gnu.org/software/xorriso/xorriso-1.2.3.tar.gz > > - Build xorriso > tar xzf xorriso-1.2.3.tar.gz > ( cd xorriso-1.2.3 && ./configure && make ) > > - Copy the MBR out of Fedora-LiveCD.iso > dd if=Fedora-LiveCD.iso bs=512 count=1 of=Fedora-LiveCD.mbr > > - Mount Fedora-LiveCD.iso > mount -o loop Fedora-LiveCD.iso /mnt > > - Create new ISO image FedoraRepack.iso > > xorriso-1.2.3/xorriso/xorriso -as mkisofs \ > -o FedoraRepack.iso -no-pad \ > -isohybrid-mbr Fedora-LiveCD.mbr \ > -c /isolinux/boot.cat \ > -b /isolinux/isolinux.bin -no-emul-boot \ > -boot-load-size 4 -boot-info-table \ > -eltorito-alt-boot \ > -e /isolinux/efiboot.img -no-emul-boot \ > -isohybrid-gpt-basdat -isohybrid-apm-hfsplus \ > -eltorito-alt-boot \ > -e /isolinux/macboot.img -no-emul-boot \ > -isohybrid-gpt-hfsplus -isohybrid-apm-hfsplus \ > -V Fedora-LiveCD \ > /mnt > > (My apologies for using the unchanged Volume Id "Fedora-LiveCD". > The booting system wants to see this in its /dev/disk/by-label/.) > > - Put on CD, DVD or BD: > xorriso-1.2.3/xorriso/xorriso -as cdrecord \ > dev=/dev/sr0 -v blank=as_needed -eject FedoraRepack.iso > > - Put on USB stick (Caution: Make sure not to overwrite your hard disk !): > dd if=FedoraRepack.iso bs=4M of=/dev/sdc ; sync > > ---------------------------------------------------------------------- > > Have a nice day :) > > Thomas > > _______________________________________________ > Syslinux mailing list > Submissions to Syslinux at zytor.com > Unsubscribe or set options at: > http://www.zytor.com/mailman/listinfo/syslinux > Please do not send private replies to mailing list traffic. >-- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.