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Re: Migrations to xorriso

From: Thomas Schmitt
Subject: Re: Migrations to xorriso
Date: Tue, 18 May 2010 10:49:56 +0200


while my local bzr upgrade problems still persist
i can view at

> xorriso -pathspecs on -as mkisofs

I would make this
  xorriso -report_about HINT -as mkisofs -graft-points

Option -report_about HINT will reduce verbosity
to the level of messages about unusual events
and remedy proposals.

Since xorriso is run in mkisofs emulation, it
seems clearer to use -graft-points rather than
xorriso option -pathspecs.

> -as mkisofs ${grub_mkisofs_arguments} --protective-msdos-label
> -o ${output_image} -r ${iso9660_dir} ${source}

The potential content of ${grub_mkisofs_arguments}
looks good so far.
I assume you have already tested your use cases.

There remain opportunities for result size

The result will be up to 426 kB larger than the
one of grub-mkisofs. (Modern mkisofs or
genisoimage would give you 300 kB extra.)


You may add mkisofs option
to avoid trailing padding of 300 kB which is only
needed if you later burn the image to a CD in
write mode TAO.
Alternatively you could allow option -no-pad in
the option interpreter of grub-mkrescue rather
than issueing:
        echo "Unrecognized option \`$option'" 1>&2

The burn program can eventually add padding.
xorriso -as cdrecord will by default use write
mode SAO if the file size is detectable.


Another 64 to 126 kB can be saved by hiding the
fact that the target is a random access file.
One would replace
    -o ${output_image}
    | cat >${output_image}
This deprives the result of the capability to
show on overwriteable media a table-of-content
with older sessions.


In my tests the size reduced result was 4 kB
smaller than the result from grub-mkisofs.

Have a nice day :)


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