title: How can I set $PS1 with Dockerfile?
body: <p>How can I set PS1 environment variable (bash prompt) in Dockerfile?<br>
  I attempted <code>ENV PS1 "\h:\W \u$ "</code><br>
  But this command does not change prompt.<br>
  I don't know why above <code>ENV</code> does not set PS1 prompt.<br>
  How can I do it?  </p>