Add "Make it obvious." to log design.
Check for program dependencies granularly.
Return, do not exit, for far greater style.
Prefix all echo messages with contextual name.
Use 'sbin' instead of 'bin' for package scripts.

Filesystem Hierarchy Standard says:

/sbin contains binaries essential for booting, restoring, recovering,
and/or repairing the system in addition to the binaries in /bin.