Since this framework is supposed to work on several
distributions, we cannot rely on a certain shell
always being available in one specific version.
Care should be taken which shebang a script uses.
As the only shell we know for sure will be there
is the ash that comes with busybox it is advised
that you write scripts that are compatible to ash
whenever possible.
So pretty much all scripts should start with
#!/bin/ash
It is guaranteed by the framework that /bin/ash
will link to mltk's busybox binary.

In case you have a fancy script that uses some bash
features it is reasonably safe to assume that the
distribution in use supplies a halfway up to date
bash version, so if you don't use any bleeding edge
features you might use
#!/bin/bash
for that script. Keep in mind that bash takes a
little while to start up (even if loaded from ram),
so don't use it if you don't have to.

You should NEVER USE /bin/sh as the shebang, as the
results are undefined. /bin/sh links to something
distribution specific, so just because it works on
one system doesn't mean it works on another
(debian/ubuntu's dash is great in breaking bash
scripts for example).
We do not modify /bin/sh so we don't accidentally
break any scripts that come with the distro (stage4).