文档介绍：Hadoop学****第一步之基础环境搭建

sudo apt-get install openssh-server openssh-client

#sudo apt-get upda hadoop 602 Jul 24 20:31
******@node1:~/.ssh$ cat >> authorized_keys
******@node1:~/.ssh$ ll
总用量 20
drwx------ 2 hadoop hadoop 4096 Jul 24 20:32 ./
drwxr-xr-x 18 hadoop hadoop 4096 Jul 24 20:31 ../
-rw-rw-r-- 1 hadoop hadoop 602 Jul 24 20:32 authorized_keys
-rw------- 1 hadoop hadoop 668 Jul 24 20:31 id_dsa
-rw-r--r-- 1 hadoop hadoop 602 Jul 24 20:31
单机回环ssh免密码登录测试
******@node1:~/.ssh$ ssh localhost
The authenticity of host 'localhost ()' can't be established.
ECDSA key fingerprint is SHA256:daO0dssyqt12tt9yGUauImOh6tt6A1SgxzSfSmpQqJVEiQTxas.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'localhost' (ECDSA) to the list of known hosts.
Welcome to Ubuntu (GNU/Linux -16-generic x86_64)
* Documentation:
270 packages can be updated.
178 updates are security updates.
New release ' LTS' available.
Run 'do-release-upgrade' to upgrade to it.
Last login: Sun Jul 24 20:21:39 2016 from
******@node1:~$ exit
注销
Connection to localhost closed.
******@node1:~/.ssh$
出现以上信息说明操作成功,其他两个节点同样操作
让主结点(master)能通过SSH免密码登录两个子结点（slave）
******@node1:~/.ssh$ scp ******@master:~/.ssh/ ./
The authenticity of host 'master ()' can't be established.
ECDSA key fingerprint is SHA256:daO0dssyqtt9yGUuImOh646A1SgxzSfatSmpQqJVEiQTxas.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'master,' (ECDSA) to the list of known hosts.
******@master's password:
100% 603 00:00
******@node1:~/.ssh$ cat >> authorized_keys
如上过程显示了node1结点通过scp命令远程登录master结点，并复制master的公钥文件到当前的目录下，
这一过程需要密码验证。接着，将master结点的公钥文件追加至authorized_keys文件中，通过这步操作，
如果不出问题，master结点就可以