Comment 2 for bug 1821263

Looking at your output, the error is happening in here:

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    Set a new process for thread id........ 139652034447104
    The new process id is.................. 20853
    • The start time is.................... 09:15:53.017537
    • Status............................... xorriso 1.4.8 : RockRidge filesystem
                                            manipulator, libburnia project.
                                            Drive current: -outdev 'stdi
    • Completed............................ 0%
    • The end time is...................... 09:15:53.145748

You can see that xorriso starts at 9:15:53 and immediately stops (crashes?), after completing 0%.
As a result, there is no "/isotest6/live-cd-2.0.1.iso" file created.

I've seen this happen with other users when there is not enough disk space, but you seem to have more than enough, so there may be another reason.

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See if you can execute xorriso manually. There might be additional error information that does not show up in the Cubic log...

$ cd /isotest6/custom-live-iso

$ sudo xorriso -as mkisofs -r -V "ISOIMAGE 2.0.1" -cache-inodes -J -l -iso- level 3 -isohybrid-mbr /usr/lib/ISOLINUX/isohdpfx.bin -c isolinux/boot.cat -b isolinux/isolinux.bin -no-emul-boot -boot-load-size 4 -boot-info-table -o "/isotest6/live-cd-2.0.1.iso" .