登录一台Ubuntu Linux系统，会提示上一次的登录信息：

Last login: Wed Jan 24 09:49:29 2018 from 25.68.xx.xx

因为不想让人知道我登录过，所以要禁掉这些信息：

vi /etc/ssh/sshd_config
修改PrintLastLog yes
为：
PrintLastLog no

[email protected]:~# service ssh restart
[email protected]:~# cat /dev/null > /var/log/wtmp
[email protected]:~# cat /dev/null > /root/.bash_history
[email protected]:~# cat /dev/null > /root/.bashrc
[email protected]:~# cat /dev/null > /root/.mysql_history
[email protected]:~# history -c