Re: customize iso image

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

sacarde wrote:
> I try to customize "debian-9.0-sparc-netinst" iso
> what suggest me to use?

The ISO production command line is recorded in many Debian ISOs as file  
  /.disk/mkisofs

Google did not find me a "9.0-sparc" ISO, but only
  debian-9.0-sparc64-NETINST-1.iso
In its file /.disk/mkisofs i read

  xorriso -as mkisofs -r -checksum_algorithm_iso md5,sha1 -V 'Debian 9.0 sparc64 1' -o /srv/debian-cd-test/debian-9.0-sparc64-NETINST-1.iso -G boot1/boot/isofs.b -B ... boot1 CD1


The file
   boot1/boot/isofs.b
is not in the ISO. There is
   /boot/isofs.b
Its content matches quite well the start of the ISO image (modulo the
effect of option -B "..."). If it was not overwritten by a file from
directory CD1, it should really be the same file that was used with
option -G.
So the re-pack command line would be something like this

  xorriso -as mkisofs \
     -r \
     -V 'Debian 9.0 sparc64 1' \
     -o my_image.iso \
     -G /path/to/extracted/iso/tree/boot/isofs.b \
     -B "..." \
     /path/to/extracted/iso/tree
  
(Option -G expects a disk file path, not a file path inside the ISO.
 "..." is really a valid parameter for option -B.)


If the clues about isofs.b were not available, i would rather cut the
first 32 KiB from the ISO:
  dd if=debian-9.0-sparc64-NETINST-1.iso bs=1K count=32 of=/tmp/my_isofs.b
and use that file with option -G:
     -G /tmp/my_isofs.b \


-----------------------------------------------------------------------

Option "-checksum_algorithm_iso md5,sha1" is actually surplus, because
it makes a setting for Jigdo file production which is not triggered by
the overall command line.
(See /.disk/mkisofs in a "i386" ISO for the many and lengthy options
 needed for that. See man xorrisofs for explanantions.)

If MD5 checksums for the overall image and the individual data files
are desired, use xorrisofs option:
  --md5

Its checksums can later be verified in the ISO file or after copying
to the installation medium.
For the superblock, the directory tree and the overall ISO:
  xorriso -md5 on -indev /dev/sr0 -check_media --
If the directory tree is ok but the overall ISO is not, then one can
scan for the addresses of damaged data files by:
  xorriso -md5 on -indev /dev/sr0 -check_md5_r sorry / --

(The checksums are for ensuring data integrity in non-hostile environments.
 Their cryptographic strength is not sufficient to protect against
 skilled intentional manipulations.)


Have a nice day :)

Thomas