说明:
The busybox applet provides general help message and allows
the included applets to be listed. It also provides optional --install command to create applet links. If you unselect this option, running busybox without any arguments will give just a cryptic error message:
$ busybox busybox: applet not found

以下位置勾选参数
OpenWrt Configuration
-> Base system > Settings
[*] Include busybox applet