Unofficial cheatcodes to backup and restore persistent data
Attached are patches to /init that implement cheatcodes to backup and restore the Knoppix persistent store image inspired by ideas from utu.
Persistent store on a USB stick or a picture card is great but these are easily lost or the file system damaged so frequent backups are a good idea. Easy, just drag and drop onto your hard drive next time you aren't running Knoppix. If that is just about never, then backup costs two reboots. The drag and drop method also requires a chunk of hard drive space the size of the persistent store, which is not always available. As utu showed, it should be possible to backup and restore persistent store using Knoppix provided you get in early enough in the boot sequence. You could boot with the debug cheatcode and do it all by hand. Instead here are a couple of cheat codes to do the job safely.
The first example might be backup to hard drive, the second to the USB stick / picture card. The first is to be preferred. You can choose where to put the backup. If you don't specify the full /aDevice/someDirectory/theFilename, the cheat code will try to fill in the missing parts from the template /mnt-system/$knoppix_dir/knoppix-data.tgz.
The backup is reasonably straight forward though rather slow. How slow depends on how much data is in your persistent store rather than how big the store is. The result is a compressed tar file that will be a lot smaller than the persistent store itself.
The restore has a surprise. It will first delete your current persistent store on the grounds that you probably need to restore because your persistent store is corrupt and cannot be used. This means the first you know about it is the 'you don't have a persistent store yet' screen pops up and if this takes you by surprise you won't type in the size quick enough and you'll have to press ctrl-alt-del to reboot and try again.
Both backup and restore seem to take a unreasonably long time when compared with similar operations done from Knoppix proper. Perhaps the BusyBox version of tar and zip are unable to exploit the multi-core capabilities of modern processors.
If you use the two cheat codes at the same time, the backup happens first. You can use this to resize your persistent store or to convert your persistent store to/from encrypted, password protected, format.
The backup file always has the extension .tgz (aka .tar.zip) and can be unpacked with tar -xzf.
The backup is not encrypted and is not password protected. The extension .zip is forseen for that but the implementation is left as an exercise for the reader.
There are two attachments to this post. They are text file patches for the /init script in the sense of the (Linux) User Command patch(1). To apply them, you would have to first unpack /mnt-system/boot/syslinux/minirt.gz. See the Wiki page on remastering.
There are two parts to the patch. The second, backup_data.txt, actually implements the new cheat codes but requires a pair of more general purpose functions implemented in the first patch, mountbypath.txt. These patches, by design, not to overlap with the (original) patch for the knoppix_data cheat code.
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