So you are working on a Linux distribution or appliance and need very fast boot-ups?
systemd can already offer boot times of < 2s (userspace only, i.e. only the bits controlled by systemd) for complete up-to-date desktop environments on simpler (but modern, i.e. SSDs) laptops if configured properly (example: http://git.fenrus.org/tmp/bootchart-20120512-1036.svg). In this page we want to suggest a couple of ideas how to achieve that, and if the resulting boot times do not suffice where we believe room for improvements are that we'd like to see implemented sooner or later. If you are interested in investing engineering manpower in systemd to get to even shorter boot itmes, this list hopefully includes a few good suggestions to start with.Of course, before optimizing you should instrument the boot to generate profiling data, so make sure you know your way around with bootchart, systemd-analyze and pytimechart! Optimizations without profiling are premature optimizations!