man useradd 状態:
useradd is a low level utility for adding users. On Debian,
administrators should usually use adduser(8) instead.
に注意してください low level utility
ユーザーを追加するには、adduser代わりに使用します。より高レベルのユーティリティです。
さらに、-dオプションを見て:
-d, --home HOME_DIR
The new user will be created using HOME_DIR as the value for the
user's login directory. The default is to append the LOGIN name to
BASE_DIR and use that as the login directory name. The directory
HOME_DIR does not have to exist but will not be created if it is
missing.
The directory will not be created if it is missing.
一般的に離れてからの維持useradd、使用adduser代わり。