Hi,     Recently, i use CentOS release 6.5 Final.    On one client, i logged with root user, on another, i logged with custom user. On the former client, i use su for changing user to another user(for example userA),     Now, i use w or who , the result don't return the userA. why?     My Linux kernal version is:                     2.6.32-431.el6.x86_64 hongchao.niu@amssy.com