[syslinux] isohybrid has 2 variants

[Thomas Schmitt]

Hi,

Ian Bannerman:
> I did not know the Perl version did not support the EFI/Mac changes.

Comparing the help texts of
  http://git.kernel.org/cgit/boot/syslinux/syslinux.git/tree/utils/isohybrid.c
and
  http://git.kernel.org/cgit/boot/syslinux/syslinux.git/tree/utils/isohybrid.in
shows that the latter lacks:

     -u --uefi   Build EFI bootable image
     -m --mac    Add AFP table support

(It should be "APM" Apple Partition Map, not "AFP" Apple Filing
 Protocol, btw.)

These features suffer from bugs, which obviously do not hamper
booting of Fedora ISOs.
  http://download.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso

Debian, Ubuntu, and Archlinux ISOs with EFI support are made
with isohybrid from xorriso/libisofs using "isohdp[fp]x*.bin"
MBRs from the SYSLINUX installation.


intrigeri:
> Would it help if someone with the needed
> Perl skills stepped up and volunteered to maintain the Perl version,
> at least to port bugfixes from the C version?

I am willing to explain what is unclear about above options.
Theory is in
  http://bazaar.launchpad.net/~libburnia-team/libisofs/scdbackup/view/head:/doc/boot_sectors.txt


intrigeri:
> https://tails.boum.org/doc/first_steps/installation/manual/mac/
Ian Bannerman:
> Now I'm confused, if Tails is able to use the .pl for the purpose of
> installing on OS X that would suggest it does have the EFI/Mac updates..?

Seems to be Macs with BIOS support/emulation.
The shown command
  perl isohybrid.pl tails-i386-0.17.1.iso
does not employ special options. 

There are even UEFI Macs which do not boot if GPT is present.
See answer by Colin Watson in:
  http://askubuntu.com/questions/37999/what-is-different-about-the-mac-iso-image


For the others, the most mac-ish ISOs are probably those of Fedora:

- isolinux.bin ISOLINUX boot image for BIOS
  reachable by EL Torito and MBR code

- efiboot.img FAT filesystem image for UEFI
  reachable by El Torito, MBR partition, GPT partition, APM partition

- macboot.img HFS(Plus ?) filesystem image for some Macs
  reachable by El Torito, MBR partition, GPT partition, APM partition

As one can see from the flaws, created by isohybrid.c --gpt --mac :
-------------------------------------------------------------------------
Volume id    : 'Fedora-Live-Desktop-x86_64-20-1'
El Torito catalog  : 42  1
El Torito cat path : /isolinux/boot.cat
El Torito images   :   N  Pltf  B   Emul  Ld_seg  Hdpt  Ldsiz         LBA
El Torito boot img :   1  BIOS  y   none  0x0000  0x00      4        2559
El Torito boot img :   2  UEFI  y   none  0x0000  0x00  10064          43
El Torito boot img :   3  UEFI  y   none  0x0000  0x00  40320        2571
El Torito img path :   1  /isolinux/isolinux.bin
El Torito img opts :   1  boot-info-table isohybrid-suitable
El Torito img path :   2  /isolinux/efiboot.img
El Torito img path :   3  /isolinux/macboot.img
System area options: 0x00000102
System area summary: MBR isohybrid cyl-align-on GPT APM
ISO image size/512 : 1950144
Partition offset   : 0
MBR heads per cyl  : 64
MBR secs per head  : 32
MBR partition table:   N Status  Type        Start       Blocks
MBR partition      :   1   0x80  0x00            0      1951744
MBR partition      :   2   0x00  0xef          172        10064
MBR partition      :   3   0x00  0x00        10284        40320
MBR partition path :   2  /isolinux/efiboot.img
MBR partition path :   3  /isolinux/macboot.img
GPT                :   N  Info
GPT backup problems:      Implausible header LBA 1951742
GPT disk GUID      :      cfbbf979fff49a49a07b0ecc3dcc1834
GPT entry array    :      16  128  overlapping
GPT lba range      :      48  1951710  1951742
GPT partition name :   1  49534f4879627269642049534f0049534f487962726964004170706c
GPT partition GUID :   1  0d4c2714741d9a4fac7e9ca380270d34
GPT type GUID      :   1  a2a0d0ebe5b9334487c068b6b72699c7
GPT partition flags:   1  0x0000000000000000
GPT start and size :   1  0  1950145
GPT partition name :   2  49534f487962726964004170706c65004170706c
GPT partition GUID :   2  9acc9f1abedd27448e31e48a7b2c4dee
GPT type GUID      :   2  a2a0d0ebe5b9334487c068b6b72699c7
GPT partition flags:   2  0x0000000000000000
GPT start and size :   2  172  10064
GPT partition path :   2  /isolinux/efiboot.img
GPT partition name :   3  49534f487962726964004170706c65004170706c
GPT partition GUID :   3  9acc9f1abedd27448e31e48a7b2c4dee
GPT type GUID      :   3  005346480000aa11aa1100306543ecac
GPT partition flags:   3  0x0000000000000000
GPT start and size :   3  10284  40320
GPT partition path :   3  /isolinux/macboot.img
APM                :   N  Info
APM block size     :      2048
APM gap fillers    :      0
APM partition name :   1  EFI
APM partition type :   1  Apple_HFS
APM start and size :   1  43  10064
APM partition path :   1  /isolinux/efiboot.img
APM partition name :   2  EFI
APM partition type :   2  Apple_HFS
APM start and size :   2  2571  40320
APM partition path :   2  /isolinux/macboot.img
-------------------------------------------------------------------------


Have a nice day :)

Thomas