1.hadoop安装好之后，执行ssh localhost无法执行，
提示“ssh: connect to host localhost port 22: Connection refused”。
2.ps -e |grep ssh查看后只有
“3748 ? 00:00:00 ssh-agent"
3.安装
sudo apt-get install openssh-server
4.启动sshd。
sudo /etc/init.d/ssh start
5.再次查看：
ps -e |grep ssh
3748 ? 00:00:00 ssh-agent
4085 ? 00:00:00 sshd
6.执行ssh localhost
Linux kali 3.14-kali1-486 #1 Debian 3.14.5-1kali1 (2014-06-07) i686
The programs included with the Kali GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Kali GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Thu Jan 15 09:21:21 2015 from localhost
成功！