Install busybox-initramfs by entering the following commands in the terminal:
sudo apt update sudo apt install busybox-initramfs
Standalone shell setup for initramfs
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-initramfs provides a simple stand alone shell that provides only the basic utilities needed for the initramfs.