porque no utilizas ubuntu builder
https://www.youtube.com/watch?v=WGj2qExNlHIquizas no te construya la iso porque no tienes demasiada capacidad en el disco a veces suele suceder ,pero puedes cambiar el destino o ruta en otro dispositivo ,disco externo ,usb etc ,solo tienes que ir a
en el terminal vim /etc/remastersys.conf
#Remastersys Global Configuration File
# This is the temporary working directory and won't be included on the cd/dvd
WORKDIR="/home/remastersys----------------------------------------------"" y aqui cambiar el destino"
# Here you can add any other files or directories to be excluded from the live filesystem
# Separate each entry with a space
EXCLUDES=""
# Here you can change the livecd/dvd username
LIVEUSER="custom"
# Here you can change the name of the livecd/dvd label
LIVECDLABEL="Custom Live CD"
# Here you can change the name of the ISO file that is created
"/etc/remastersys.conf" 35L, 884C 1,0-1 Haut