linux fedora 12 下 root用户通过x界面登录默认是禁用的，网上查询启用方法，google中文里搜索，说是修改/etc/pam.d/gdm文件，注释掉一行就可以，但修改过却还不能登录的，于是在google.com里搜索，看老外们怎么讲查到下面一篇文章，里面说要修改两个文件，
/etc/pam.d/gdm
/etc/pam.d/gdm-password
这样才可以，明确指出不像Ubuntu那样。
原文如下，作者说直接修改root为其它随意的字符串，如test，但或许注释会更好。
http://www.linuxreaders.com/2009/11/19/root-login-on-fedora-12/
Root Login on Fedora is not as easy as Ubuntu Root Login, here you need to modify two files to get root access.
You need to modify content of following files
/etc/pam.d/gdm
/etc/pam.d/gdm-password
You’ll find pam_succeed_if.so user != root quiet in above files, replace root with anything e.g test
I replaced root with test & was able to login to system using root.
OR Comment the entire line.
[Comment the entire line recommend!]