配置免密登錄：
master到node01-node03的免密登錄
1、在master上用username依次執行：
ssh-keygen chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys
cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
這時，authorized_keys中應該有master機器名的字樣
2、接下來將生成的authorized_keys複製到其他節點對應位置：
scp ~/.ssh/authorized_keys username@node01:~/.ssh/authorized_keys
scp ~/.ssh/authorized_keys username@node02:~/.ssh/authorized_keys
scp ~/.ssh/authorized_keys username@node03:~/.ssh/authorized_keys
至此，master對其他節點ssh無密碼登陸配置成功，可以ssh下對應節點嘗試是否成功。
發現免密登錄不成功，檢查安全登錄日誌（sudo cat /var/log/secure）：
Jul 24 14:53:51 serv61 sshd[6620]: warning: /etc/hosts.allow, line 13: missing ":" separator
Jul 24 14:53:51 serv61 sshd[6620]: Authentication refused: bad ownership or modes for directory /home/zyhadoop
Jul 24 14:53:54 serv61 sshd[6620]: Accepted password for zyhadoop from 10.224.234.201 port 39770 ssh2
Jul 24 14:53:54 serv61 sshd[6620]: pam_unix(sshd:session): session opened for user zyhadoop by (uid=0)
Jul 24 14:54:10 serv61 sudo: zyhadoop : TTY=pts/1 ; PWD=/home/zyhadoop ; USER=root ; COMMAND=/bin/cat /var/log/secure
Jul 24 14:54:10 serv61 sudo: pam_tally2(sudo:setcred): unknown option: no_magic_root
觀察到 /home/zyhadoop的用戶權限有問題，修改目錄權限：
chmod 755 zyhadoop
免密登錄成功。