An example set of service definition directories.

 ok-all is the bundle containing all the services used
for normal operation of the machine this set has been taken
out of; the stage 2 init script of this machine is basically
"s6-rc-init && s6-rc change ok-all".

 ok-all contains ok-local, ok-lan and ok-wan, all bundles
each containing their own services.

 "00" is the service at the bottom of the dependency graph.
So 00/up is the first script that is run by the initial
"s6-rc change ok-all" command.