This goes to the heart of Linux. If you HAVE root you can add commands with symbolic links to busybox or toolbox. Simply make a symbolic link the busybox or toolbox binary and give it the name of the command you want to add. If you do not have root you can type busybox command name [ args ] and if busybox is present and has the command defined you can run it without root provided root is not needed to run the command. The toolbox binary also works this way.
March 26 2017