the problem I see is that the /tmp
filesystem is too small to store the temporary files needed to build the ISO:
i.e. you are going to remaster approx. 3.8 GB, that once compressed will result in something like 1.3 GB, that the required free space in /tmp.
It appear you have enough free space on '/' filesystem, i.e. 33 GB free, so I suggest this:
mkdir /temp # this will create a temp dir on / filesystem
mylivecd --gzip --tmp /temp --nodir ^/temp mylivecd.iso
the --gzip option
provide lesser compression but it is approx 3x faster, good for testing,
the option --tmp /temp
tell to mylivecd program to store the temporary files in /temp
the option --nodir ^/temp
tell to mylivecd to not backup /temp directory (should be excluded automatically ... just to be sure).