remastering a distribution is intended to meet a specific need for someone or party. it is made because no distribution meets their needs. this time i will explain remastersys available on ubuntu repository. first install remastersys
# apt-get install remastersys
the system will download the file and any program and libraries needed by remastersys and also install them. now let's make a change to the system for example we install kplayer
# apt-get install kplayer
again the system will download and install the program. then run remastersys or remastersys-gui for GUI
choose backup complete system including user data
this way, everything's clear. you can backup the entire system and a new ISO image will be created. burn the image to a disc with k3b or to flash drive with unetbootin then boot from it .