Ramdisk and partial remastering in Knoppix 7

[Capricorny]

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Recapitulation: We can have a full-DVD-size LiveUSB on an 8 Gb Class 10 SDHC device. This device
may be serially updated with compressed image additions without requiring any additional workspace;
without requiring any additional system, real or virtual, to manage this process; and without
any significant time expenditure for these performing these updates.
The convenience of temporary persistence may be maintained, while greatly reducing the magnitude
of the hazard in occasional inadvertent ruination of this 'persistent' image, since these
successive updates preserve well-tested material in more safely situated in more permanent
compressed images.

For more heavy installs. I will strongly recommend using a 16 GB stick, for in this scheme nothing is ever purged, which means, for example, that you will get several instances of the apt data, essentially one on each KNOPPIX[N] image. In my own use case, I have by now purged about 2GB of programs/data, and added about 3 GB on 7.0.2. Of course, this is "real world" use of Knoppix, and most users might do less, but if I had used this method, I would have had about 6GB total in cloop images by now, and I advise people to be defensive with regard to the space overhead of different copy/compress/backup methods.

It does not go on indefinitely, for the vast majority of uses, 16GB media will be enough. I have also experimented with >4GB persistent image, for example using several (uncompressed) image files, but I think an adaptation of the method presented here is better in most cases.
I think this is also a nice illustration of what I have come to think is the basic rule of remastering: If you don't know exactly why you need it, and why the alternatives are indequate, don't do it.

I'd like to mention one way this can bu used for (sort of) incremental backups: If you call the KNOPPIX[1|2|3...] images something else, for example knoppix-20120620.cloop, and store it at your backup location, while you continue to use the same knoppix-data.img at next boot, instead of forcing creation of a new image, you may cloop-mount this image and recreate the knoppix-data.img of that day from it. They may of course grow ever larger, but if you purge your persistent image, they may also shrink.

Myself, I make tarballs (.tgz files) of the knoppix-data.img for backups, but this way, I don't have the chance to start afresh with the persistent image without remastering - like I can if I decide to use the cloop backup as KNOPPIX1 and start a new .img file. I should add that I don't use the persistent store for much data - they are stored on a volume mounted on /store in my setup, and this volume is stable across OS versions and backed up separately. Some of it dates back to Slackware days of 1995..