busybox-udeb binary package in Ubuntu Trusty arm64

 BusyBox combines tiny versions of many common UNIX utilities into a single
 small executable. It provides minimalist replacements for the most common
 utilities you would usually find on your desktop system (i.e., ls, cp, mv,
 mount, tar, 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-udeb is used by the debian-installer, so unless you are working on
 the debian-installer, this package is not for you. Installing this
 on your Debian system is a very, very bad idea. You have been warned.

Source package