*Linux ash prompt can't work about PS1='[\u\@\h \W]# '

In the busybox, you must turn on CONFIG_FEATURE_SH_FANCY_PROMPT

Symbol: FEATURE_EDITING_FANCY_PROMPT
x Prompt: Fancy shell prompts
x Defined at libbb/Config.in:97
x Depends on: FEATURE_EDITING
x Location:
x -> Busybox Settings
x -> Busybox Library Tuning
x -> Command line editing (FEATURE_EDITING [=y])

 Location:                                                                                                              x
  -> Busybox Settings                                                                                                  x
       -> Busybox Library Tuning                                                                                          x
       -> Command line editing (FEATURE_EDITING [=y])