sudo apt-get install openssh-server 需要安装 sudo apt-get update 404错误解决办法 The authenticity of_sudo apt-server

Ubuntu 11.04 (Natty) 已经停止支持,但可以使用old-releases源了,先备份源列表文件:
sudo cp /etc/apt/sources.list /etc/apt/sources.list.backup

sudo gedit /etc/apt/sources.list
把里面的内容替换为以下内容:
deb http://old-releases.ubuntu.com/ubuntu/ natty main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ natty-security main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ natty-updates main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ natty-proposed main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ natty-backports main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ natty main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ natty-security main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ natty-updates main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ natty-proposed main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ natty-backports main restricted universe multiverse

重载源列表,使配置生效:
sudo apt-get update

安装SSH服务器和客户端:

sudo apt-get install openssh-server openssh-client

源文:http://www.oschina.net/question/813663_115809

1,检查服务是否启动：
ps -ef| grep sshd

如果只有ssh-agent那ssh-server还没有启动，
需要/etc/init.d/ssh start，
如果看到sshd那说明ssh-server已经启动了。

2，master配置免密码：
ssh-keygen -t dsa -P ‘’ -f ~/.ssh/id_dsa
cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys

3，ssh slave1 连接The authenticity of host can't be established错误：
修改/etc/ssh/ssh_config文件的配置，以后则不会再出现此问题
最后面添加：
StrictHostKeyChecking no
UserKnownHostsFile /dev/null

4,ssh slave1 提示输入密码时输入slave1的密码  变成root@slave1  
敲命令ssh master 提示输入密码时输入master的密码变成root@master

-----ssh配置连通成功