ssh-keygen -t rsa
-- 三台分别执行  ssh-keygen -t rsa   不用输入密码，

一路回车就行

#slave1       cp   ~/.ssh/id_rsa.pub   ~/.ssh/slave1_id_rsa.pub   

                   scp  ~/.ssh/slave1_id_rsa.pub      master:~/.ssh/
#slave2       cp   ~/.ssh/id_rsa.pub    ~/.ssh/slave2_id_rsa.pub

                   scp   ~/.ssh/slave2_id_rsa.pub   master:~/.ssh/
#master      cat  ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys      

                   cat  ~/.ssh/slave1_id_rsa.pub >> ~/.ssh/authorized_keys

                   cat  ~/.ssh/slave2_id_rsa.pub >> ~/.ssh/authorized_kyes

                   这样master就能免密访问slave，比如ansible的master操作。

                   如果要让slave免密访问master就把authorized_kyes拷贝到slave

                   scp  ~/.ssh/authorized_keys slave1:~/.ssh

                   scp  ~/.ssh/authorized_keys slave2:~/.ssh

ssh 偷懒 ssh-copy-id