出现错误的原因， /etc/pam.d/vsftpd的脚本没有引入相应的包，导致验证用户失败 。所以解决的办法就是用下面的脚本替换掉vsftpd里面的脚本。
#%PAM-1.0
#session optional /lib64/security/pam_keyinit.so force revoke
#auth required /lib64/security/pam_listfile.so item=user sense=deny file=/etc/vsftpd/ftpusers onerr=succeed
#auth required /lib64/security/pam_unix.so
#auth include /etc/pam.d/password-auth
#account include /etc/pam.d/password-auth
#session required /lib64/security/pam_unix.so
#session include /etc/pam.d/password-auth
auth required /lib64/security/pam_listfile.so item=user sense=deny file=/etc/ftpusers onerr=succeed
auth required /lib64/security/pam_unix.so shadow nullok
auth required /lib64/security/pam_shells.so
account required /lib64/security/pam_unix.so
session required /lib64/security/pam_unix.so