Has this thread been renamed ? I like the new title. Lots. It is exactly what I was looking for.

Are the instructions for the CD or the DVD ? For the CD you may need /lots_of_free_space but for the DVD you need /super_lots_of_free_space. Like about 5 times as much so you've got to plan ahead.

I tried following the instructions with the DVD (6.4.3 EN). The 'main' command did not scale so well. It failed claiming I was out of virtual memory. The 'main' command (taken I see from http://www.knoppix.net/wiki/Knoppix_Remastering_Howto)

Code:
mkiosfs ... | create_compressed_fs ... > KNOPPIX/KNOPPIX
is a pipe, which is usually good. Usually the right-hand side consumes data as fast as the left-hand side produces it. The pipe means no (large) temporary files are needed and it all runs faster as a result.

However, a look at the output of create create_compressed_fs -h, particularly the description of the -s flag and the stuff at the end, suggests the pipe is a bad idea: the right-hand side is going to buffer its entire input before it processes anything.

If you are remastering the CD, you might have enough real memory and/or enough swap (the HowTo describes how to create a 1 Gb swap) but for remastering the DVD you're looking at 8 Gb or so. I have no other use for an 8 Gb swap partition, so I split the main command in two and used a temporary file (a bit like using the -f option of create_compressed_fs).

The 'main' command examples all prefix the create_compressed_fs with nice -5. This too I find strange. The right hand side runs at a lower priority that the left, so you would expect data to pile up in the pipe even if you use the -s or -f options of create_compressed_fs. The right hand side takes a long time to run and uses a lot of processor. The intention of the nice -5 is run the compression at a low priority so you can do other 'stuff' while you wait. But it uses up a lot of memory too so doing other 'stuff' may not be all that great. Me, I left off the nice -5 and got in some zeds.

The instructions do cover in detail how to meet the challenge of getting the new KNOPPIX image onto the USB and how to clean up the contents of the old persistent store. However, I had to read it three times before it was clear that you don't have to do it the 'risky' bit booting Knoppix with the debug cheatcode.

So, for the benefit of those new to Knoppix and remastering, once you have created the new KNOPPIX image:
- shutdown your PC / laptop;
- remove the USB;
- boot your Knoppix Live CD (the one you installed to USB with the first place);
- insert the USB stick again;
- now follow the instructions.

Also for the benefit of those new to Knoppix and remastering:
- you should run all the commands from a 'root shell'
- if you don't, you'll have to prefix most commands with sudo
- even so, the command with the '>' may fail.

Those new to Knoppix and remastering may also be a little nonplussed by the suggestion that what they put on the new image is an entirely a free choice:
- update/remove/install software until you are happy/fed up/get a life;
- you don't want /home in the new image (that's your stuff)
- you don't want /var in the new image (stuff that changes all the time);
- take /home and /var from the old image
- it is a reasonable bet everything else should go in the new image
- until you know better
- when you clean up your knoppix-data.img, delete everything except /home and /var.

I working my way towards describing how much disk space you (might) need to remaster the DVD. To do that I'm going to have to show you how I did it. I do everything a directory created for the purpose and always write to a subdirectory. Fewer disasters that way. The subdirectories may be real directories or symbolic links or mount points (my favourite). That's not important at this stage. I put all the scary commands into a script so that next time I remaster, I won't have to type them in or copy/paste them from a web page. Fewer disasters that way.

Code:
#!/bin/bash

command=$1; shift;
operand=$1; shift;

case "${command} ${operand}" in
  ("copy source")
    excludes="--exclude=/home --exclude=/lost+found --exclude=/var";
    sudo rsync -ax --delete ${excludes} /UNIONFS/ knoppix_source;
    sudo rsync -ax /KNOPPIX/home /KNOPPIX/var knoppix_source;
    sudo cp -p /KNOPPIX/etc/fstab knoppix_source/etc;
    ;;
  ("make isofs")
    sudo chmod 1000:1000 knoppix_tmpiso;
    sudo mkisofs -R -U -V "KNOPPIX.net filesystem" -publisher "KNOPPIX www.knoppix.net" -hide-rr-moved -cache-inodes -pad knoppix_source > knoppix_tmpiso/knoppix.iso
    ;;
  ("compress isofs")
    mkdir -p knoppix_master/KNOPPIX;
    sudo create_compressed_fs -b -B 65536 knoppix_tmpiso/knoppix.iso knoppix_master/KNOPPIX/KNOPPIX;
    echo "Now reboot to CD";
    ;;
  ("backup usb")
    mkdir -p knoppix_backup/KNOPPIX;
    cp -p knoppix_usb/KNOPPIX/KNOPPIX knoppix_usb/KNOPPIX/knoppix_data knoppix_backup/KNOPPIX;
    ;;
  ("copy master")
    cp -p knoppix_master/KNOPPIX/KNOPPIX knoppix_usb/KNOPPIX;
    ;;
  ("mount data")
    mkdir -p knoppix_data;
    sudo mount -o loop knoppix_usb/KNOPPIX/knoppix-data.img knoppix_data;
    ;;
  ("prune data")
    cd knoppix_data;
    sudo rm -fr $(ls -ignore=home --ignore=var);
    cd ..;
    ;;
  ("umount data")
    sudo umount knoppix_data;
    rmdir knoppix_data;
    ;;
  (*)
    echo oops;
    ;;
esac
So, meet the directories:

knoppix_source - where the filesystem for the new image is assembled. It has to be a Linux filesystem. It must be at least the size of /UNIONFS.
Budget 10 Gb.

knoppix_tmpiso - where the uncompressed iso image goes. It can't be a FAT filesystem as it takes a single file bigger than 4 Gb. The iso file is slightly smaller than its source.
Budget 10 Gb.

knoppix_master - where the compressed iso image (the new Knoppix image) goes. This can be a FAT filesystem, since the image will be copied to a FAT filesystem on USB. This also means it can't be bigger than 4 Gb (the original 6.4.3 is 3.5 Gb).
Budget 4 Gb.

knoppix_backup - back up the old Knoppix image and knoppix-data.img goes here. I'm using a 1 Gb knoppix-data.img. Again, can be any filesystem, even FAT.
Budget 5 Gb.

knoppix_usb - the USB installation that is being remastered is under here.
This already exists on the USB so ...
Budget 0 Gb.

That's 29 Gb total but if you use just one large Linux partition and delete stuff as you go along you can do it in 20 Gb. I don't know what you'd need to remaster the CD but I guess 4 Gb would be enough.

Where does all this disk space come from ?

I'm lucky in that I when I remaster I don't have ntfs between me and my hard drive. I only have lvm2 so I can whip up a new filesystem in less time that it takes to type this.

Many (me included) first try Knoppix because they want to try Linux but do not want to touch Windows. If you are one of those, my advice is don't touch Windows (aka "Don't try this at work"). Find another way or find something else to do.

I don't know how inexpensive hard disks or USB sticks are in $ but my advice would be to buy a USB stick big enough to do job. That's a 32 Gb stick for the DVD and may be only a 4 Gb for the CD.

You would need to plan ahead. Figure out what goes in which partition, how big each partition must be, partition and format the USB all before you install Knoppix to USB. Me, I'm already on my third iteration.