At this time, May, 2013, see remastersys for new developments.
To make a .iso copy of your Debian based system, the Ubuntu Remastersys application can be installed in the following manner:
(i) Rename /usr/share/doc/libglib2.0-bin, if that file is present. Otherwise it will hinder the installs below. If you are worried about giving it a new name, return the original name after Remastersys is installed.
(ii) From http://packages.debian.org/squeeze/live-initramfs download and install live-initramfs, number 2.0.15-1 or later, using GDebi installer.
(iii) From https://launchpad.net/ubuntu/+source/glib2.0/2.31.12-0ubuntu1, download glib2.0_2.31.12-0ubuntu1.debian.tar.gz, or a later version, and put it in your Downloads Directory. Install:
tar -xvf ~/Downloads/glib2.0_2.31.12-0ubuntu1.debian.tar.gz .
(iv) From http://packages.debian.org/sid/amd64/libglib2.0-0/download, download libglib2.0-0_2.32.3-1_amd64.deb, or a later version, and put it in your home directory. Install:
sudo dpkg -i libglib2.0-0_2.32.3-1_amd64.deb .
(v) In Synaptic/Settings/Repositories/Other Software/Add add the following repository:
deb-src http://www.remastersys.com/repository squeeze/ .
(vi) Check /etc/apt/sources to be sure this repository is open.
(vii) Reload Synaptic, find remastersys and install it in the usual way. Also, install remastersys-gui, provided it is present, which it probably won't be, in which case, don't worry about it, as it was probably already in the install.
This should put a flock of remastersys tools in the Preference category of your Main Menu. Launch Remastersys Backup and click Backup to make a copy of your total operating system. It will appear as custom.iso in /home/remastersys/remastersys. If you have trouble with the GUI functioning, then launch remastersys by entering the following in the terminal:
sudo remastersys backup custom.iso.
Finish by burning custom.iso to a DVD to have a new installation disk that can be used to run or install your system on any computer. Before you run remastersys, clean your system of trash, temporary files, cookies, music, videos, movies, etc. The .iso must be under about 4.7 GB to fit on a standard DVD. When you are asked where to put Grub, choose Master Boot Record (MBR) to eliminate later problems. If the new install does not boot, reboot from the remastersys disk and run Remastersys Grub Restore, which is one of the available tools.
To start the installer of a remastered copy of a system, put the following in the terminal after the copy has been loaded:
sudo remastersys-installer gui.
Complete command line information for Remastersys is at remastersys.com, and additional information is given in the LXDE Guide.