##查看cron运行日志
tail -f /var/log/cron报如下错误：
May 8 10:14:01 localhost crond[9399]: (root) FAILED to authorize user with PAM (Module is unknown) May 8 10:14:01 localhost crond[9400]: (root) FAILED to authorize user with PAM (Module is unknown)##网上有如下解决方法：
禁用SELinux,可以使用getenforce命令查看是否禁用。修改/etc/cron.allow，添加 root myuser 修改/etc/pam.d/crond，把把所有required改成sufficient，这个可能对非root用户管用。 # # The PAM configuration file for the cron daemon # # # No PAM authentication called, auth modules not needed account required pam_access.so account include password-auth session required pam_loginuid.so session include password-auth auth include password-auth##最终解决办法： 重启crond服务
/etc/init.d/crond restart参考：
https://www.centos.org/forums/viewtopic.php?t=61414https://opensource4admin.wordpress.com/2014/07/31/failed-to-authorize-user-with-pam-module-is-unknown-solved/http://bluemood.blog.51cto.com/1142811/953078/http://www.linuxquestions.org/questions/linux-security-4/failed-to-authorize-user-with-pam-permission-denied-4175492110-print/