比较简单，这样就可以了
cat > /var/spool/cron/root <<EOF
* * * * * /usr/sbin/ntpdate cn.pool.ntp.org >> /var/log/ntpdate.log
EOF
额外的资料
1.copy or backup
#crontab -l > /tmp/root.crontab
2.edit
edit root.crontab by vi,emacs, ed ,etc etc .
3.activate
#crontab /tmp/root.crontab
关闭ssh的HostKeyChecking
The authenticity of host ‘11.22.33.44 (11.22.33.44)’ can’t be established.
RSA key fingerprint is b7:2f:12:ff:a8:97:a3:09:13:41:c0:e8:ab:7a:6f:ed.
Are you sure you want to continue connecting (yes/no)?
RSA host key for 11.22.33.44 has changed and you have requested strict checking
ssh到远程服务器时时，是否觉得很烦
修改下ssh的配置就可以了,当然，必须确定远程主机是可信任的
vi /etc/ssh/ssh_config
将
# StrictHostKeyChecking ask
修改为
StrictHostKeyChecking no
service sshd reload
这样就可以了
如果想单次连接取消，则可以用命令
ssh -o StrictHostKeyChecking=no 192.168.6.12
其他命令
ssh -o StrictHostKeyChecking=no -o CheckHostIP=no -o UserKnownHostsFile=/dev/null 192.168.6.12