2. Software requirements

You need:

• a fully working Linux system (any version should be OK);
• the common gzip compression utility, or alternatively bzip2 that you find on ftp://sunsite.unc.edu:/pub/Linux/utils/compress; this tool compresses better than gzip, but it's also a wee bit slower and consumes a lot of memory;
• the upx executable compressor, whose home page is at http://cdata.tvnet.hu/~ml/upx.html and http://wildsau.idv.uni-linz.ac.at/mfx/upx.html;
• the zlibc package, available on ftp://sunsite.unc.edu:/pub/Linux/libs/compression. It's called zlibc-X.X.tar.gz, where X.X is the latest version.

There are other executable compressors. One is gzexe (forget it), while tcx was probably the best before upx became available; yet another is tzx, in theory better than tcx. The thing is, it screwed everything up when I tried it on a spare PC, though I'm not sure if I did something wrong. You had better stick with upx: it's reliable, efficient, and very handy.

There are kernel patches that provide transparent file system compression a la Stacker, but as of this writing none of them has yet a reputation for stability and reliability. For safety's sake, steer clear.