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Re: arm64 and isohybrid


Steve McIntyre:
> I'm also *way* overdue on switching all of debian-cd over to using
> xorriso and using native xorriso options totally rather than the
> -as-mkisofs stuff equivalents. But that's a topic for another day...

You will be a trailblazer. Nobody else does this, except me,
when testing the new feature to generate commands from the
analyzed boot equipment of ISOs.

The -as mkisofs command is an offcial part of xorriso.
You may well stay with it as long as there are no demands
which cannot be fulfilled with its option interface.
(E.g. it is not very suitable for multi-session and
 allows few file manipulations inside the ISO.)

One may question the beauty of

-boot_image any efi_boot_part=--efi-boot-image
-boot_image any cat_path='/boot.catalog'
-boot_image any efi_path='/boot/grub/efi.img'

relative to

-efi-boot-part --efi-boot-image
-c '/boot.catalog'
-e '/boot/grub/efi.img' -no-emul-boot

I had few clue of boot equipment when designing the -boot_image
command. It is flexible enough to keep up with new demands.
But it is far from being clear. The first parameter, which was
intended to distinguish boot loaders, is mostly wasted.
Actually i could need a new straighforward language to
describe El Torito and the System Area.

As said, i am working on a feature to tell commands from
ISOs. There are still problems with commands which take
as input data from outside the ISO filesystem.
E.g.: -isohybrid-mbr or -append_partition.

When this feature is completed, then it will be halfways usable
as translator from -as mkisofs options to -boot_image commands.
Just inquire some ISO that was produced by xorriso -as mkisofs.

E.g. an amd64-netinst will yield:

-boot_image isolinux system_area=...what.path.to.use.here.?...
-boot_image isolinux partition_table=on
-boot_image any partition_cyl_align=on
-boot_image any partition_offset=0
-boot_image any partition_hd_cyl=64
-boot_image any partition_sec_hd=32
-boot_image any apm_block_size=2048
-boot_image any cat_path='/isolinux/boot.cat'
-boot_image isolinux bin_path='/isolinux/isolinux.bin'
-boot_image any platform_id=0x00
-boot_image any emul_type=no_emulation
-boot_image any load_size=2048
-boot_image any boot_info_table=on
-boot_image any next
-boot_image any efi_path='/boot/grub/efi.img'
-boot_image any platform_id=0xef
-boot_image any emul_type=no_emulation
-boot_image any load_size=458752
-boot_image isolinux partition_entry=gpt_basdat
-boot_image isolinux partition_entry=apm_hfsplus

This will still not be a no-brainer. One has to check
each command whether one wants to fixely set its parameter
or rather depend on xorriso defaults.
E.g. the load_size=458752 is actually the size of efi.img
and thus variable. So one better omits that command and
lets xorriso use the data file size.
On the other hand load_size=2048 is an important fixed
parameter for ISOLINUX BIOS boot images. It corresponds to
-as mkisofs -boot-load-size 4.

(Ceterum censio partition_entry=apm_hfsplus
 is not appropriatum and esse delendam.)

Have a nice day :)


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