the cloop[0] system from knoppix is something i use often to back up arbitrary file systems. debian has the cloop-utils which includes create_compressed_fs, and this is great for making compressed copies of file systems which can then be read without uncompressing the whole blob. however i have found debian's cloop-src module to be problematic in that i have never been able to get it to compile. the actual module comes as source only, and without this part it is not possible to read the backups without uncompressing, which is a shame. in fact it appears debian has recently removed cloop from debian testing[1] for this reason. so it is still necessary (and enjoyable) to have knoppix around to use the decompression system, although it is a huge pain to do it this way. i hope debian is able to get things sorted finally with cloop-src! that would be great.

[0]https://en.wikipedia.org/wiki/Cloop [1]https://tracker.debian.org/pkg/cloop