在ubuntu登錄界面，輸入密碼后，出現一個界面后一閃而過又返回登錄界面。查看auth.log發現如下錯誤

May 15 15:42:19 tim-vm lightdm: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0)May 15 15:42:20 tim-vm lightdm: PAM unable to dlopen(pam_kwallet.so): /lib/security/pam_kwallet.so: cannot open shared object file: No such file or directoryMay 15 15:42:20 tim-vm lightdm: PAM adding faulty module: pam_kwallet.soMay 15 15:42:20 tim-vm lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "tim"May 15 15:42:24 tim-vm lightdm: pam_unix(lightdm-greeter:session): session closed for user lightdm

google之后，在askubuntu發現了同樣的錯誤http://askubuntu.com/questions/161736/ubuntu-box-just-redisplaying-login-screen-after-update。

是因為.Xauthority文件權限的問題，這個權限都變成了root.

將其更改為用戶名即可