You can quit
<command>adduser
</command> any time by typing
<keycombo><keycap>Ctrl
</keycap><keycap>C
</keycap></keycombo>, and at the end you will have a chance to approve your new user or simply type
<keycap>n
</keycap> for no. You might want to create a second new user so that when you edit
<systemitem class="username">jack
</systemitem>'s login files, you will have a hot spare in case something goes wrong.