[root@ok ~]# vim /etc/pam.d/su

  1 #%PAM-1.0
  2 auth            sufficient      pam_rootok.so
  3 # Uncomment the following line to implicitly trust users in the "wheel" group.
  4 #auth           sufficient      pam_wheel.so trust use_uid
  5 # Uncomment the following line to require a user to be in the "wheel" group.
  6 #auth           required        pam_wheel.so use_uid
  7 auth            include         system-auth
  8 account         sufficient      pam_succeed_if.so uid = 0 use_uid quiet
  9 account         include         system-auth
 10 password        include         system-auth
 11 session         include         system-auth
 12 session         optional        pam_xauth.so
将第４行的#号去掉，然后将登陆用户加入 wheel组
[root@ok ok]# usermod -G wheel ok
[ok@ok ~]$ su 
[root@ok ok]#
su直接切换成root