Slax is a modern, small, and fast Linux operating system with a modular approach and outstanding design. Despite its small size, which is below 200 megabytes, Slax provides a wide collection of pre-installed software for daily use, including a well organized graphical user interface (KDE4) and useful recovery tools for system administrators. The modular approach gives you the ability to include any other software in Slax easily, by downloading a module with the software, without having to install or configure it.
sqlzma is a patch against lzma and squashfs that makes squashfs support both LZMA compression and ZLIB compression. A squashfs image file that uses LZMA compression has no backward compatibility, but the patched squashfs and its tools can handle the old squashfs image generated by the unpatched squashfs-tools.
unionfs is deprecated
Even if the development of unionfs continues, it's deprecated. Use aufs instead, which is a re-implemented and re-designed unionfs from the scratch. See aufs.cvs.sourceforge.net/aufs/aufs/