systemd
1. cgroups.txt
http://www.kernel.org/doc/Documentation/cgroups/cgroups.txt
2. Original Design Document
http://0pointer.de/blog/projects/systemd.html
3. Interface Stability Promise
http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise
4. XDG Base Directory specification
http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
5. If run inside a Linux container these arguments may be passed as command line arguments to systemd itself,
next to any of the command line options listed in the Options section above.
If run outside of Linux
containers, these arguments are parsed from /proc/cmdline instead.
