busybox
FIPS 140-3Developer toolsThe Swiss Army Knife of Embedded Linux
The Swiss Army Knife of Embedded Linux
With a minimal size, BusyBox is a very good ingredient to craft space-efficient distributions.
BusyBox combines tiny versions of many common UNIX utilities into a single small executable. It provides replacements for most of the utilities you usually find in GNU fileutils, shellutils, etc. The utilities in BusyBox generally have fewer options than their full-featured GNU cousins; however, the options that are included provide the expected functionality and behave very much like their GNU counterparts. BusyBox provides a fairly complete environment for any small or embedded system.
For more details, visit https://wikipedia.org/wiki/BusyBox.