免密码ssh设置现在确认能否不输入口令就用ssh登录localhost: $ ssh localhost如果不输入口令就无法用ssh登陆localhost，执行下面的命令：1. 并修改hosts映射:    添加：(配置三台机器hosts,保证可以互相访问)  $ vi /etc/hosts    127.0.0.1       localhost.localdomain   localhost    192.168.126.10  master.localdomain master    192.168.126.20  slave1.localdomain slave1    192.168.126.30  slave2.localdomain slave22. 生成三台机器的密钥和公钥     $  ssh-keygen  -t rsa -f ~/.ssh/id_rsa #生成秘钥和公钥    $ cat ~.ssh/id_rsa.pub >> ~/.ssh/authorized_keys //把当前主机的公钥添加到authorized_keys文件    $ scp .ssh/id_rsa.pub root@192.168.126.10:/home/hadoop/.ssh/authorized_keys_slave1 //复制slave1公钥添加到authorized_keys_slave1文件    $ scp .ssh/id_rsa.pub root@192.168.126.10:/home/hadoop/.ssh/authorized_keys_slave2 //复制slave2公钥添加到authorized_keys_slave2文件3.把slave1和slave2的公钥追加到authorized_keys    $ cat /home/hadoop/.ssh/authorized_keys_slave1 >> /home/hadoop/.ssh/authorized_keys    $ cat /home/hadoop/.ssh/authorized_keys_slave2 >> /home/hadoop/.ssh/authorized_keys     master配置     ################master#################    $ cat id_rsa.pub >> authorized_keys    $ cat authorized_keys_slave1 >> authorized_keys    $ cat authorized_keys_slave2 >> authorized_keys    $ chmod 644 authorized_keys//修改权限      ######################################                                                4.把主机的公共密钥复制到slave1和slvae2    $ scp id_rsa.pub root@192.168.126.20:/home/hadoop/.ssh/authorized_keys_master    $ scp id_rsa.pub root@192.168.126.30:/home/hadoop/.ssh/authorized_keys_master    slave1配置    ##################slave1#####################    cat id_rsa.pub >> authorized_keys    cat authorized_keys_master >> authorized_keys    chmod 644 authorized_keys    ######################################        slave2配置    ##################slave2#####################    cat id_rsa.pub >> authorized_keys    cat authorized_keys_master >> authorized_keys    chmod 644 authorized_keys  #######################################

最后测试：

master主机访问slave1和slave2:

ssh 192.168.126.20 //回车，如果切换到slave1,则访问成功。slave3同理。