ubuntu 突然不能 sudo成功，报错su: Authentication failure

通过查看日志：

            /var/log/auth.log

报错：

 su[9959]: PAM unable to dlopen(pam_rootok.so): /lib/security/pam_rootok.so: cannot open shared object file: No such file or directory

 su[9959]: PAM adding faulty module: pam_rootok.so

 su[9959]: PAM unable to dlopen(pam_unix.so): /lib/security/pam_unix.so: cannot open shared object file: No such file or directory

 su[9959]: PAM adding faulty module: pam_unix.so

 su[9959]: pam_authenticate: Authentication failure

 su[9959]: FAILED su for root by dev

 su[9959]: - /dev/pts/27 dev:root

解决办法：apt-get install libpcre3 login

注意：如果你是第一次安装，还没有设置过/etc/sudoers，请使用visudo进行设置，具体教程请baidu