SSH互信免密码登陆:       # 每台服务器操作一次.

1.1 配置远程主机无密码登录   # 推荐
ssh-keygen -t rsa -f .ssh/L-0 -P ''                            # 生成密钥
ssh-keygen -t rsa -f .ssh/L-1 -P 'wdqdmm@L'             # 生成密钥
-centos8
ssh-keygen -t ed25519 -f .ssh/L-0 -P '';
ssh-keygen -t ed25519 -f .ssh/L-1 -P 'wdqdmm@L';
ssh-copy-id -i .ssh/id_rsa.pub root@主机 -p 55555   # 向被授权的主机上拷贝,端口加-p.
--------------------------------------------------------
ssh-copy-id -i .ssh/id_rsa.pub root@172.24.0.13 
ssh-copy-id -i .ssh/id_rsa.pub root@172.24.0.14
-------------------------PublicKey---只配置公钥登录-------------------
vi /etc/ssh/sshd_config
PubkeyAuthentication yes # 授权公钥登录
PasswordAuthentication no
UsePAM no
-------------------------重启sshd服务--------------------------------
# systemctl restart sshd.service  # centos系统
# /etc/init.d/sshd restart        # ubuntu系统

1.2 配置hadoop-master本机无密码登录
ssh-keygen -t rsa                                # 生产秘钥
# 将公钥追加到”authorized_keys”文件
cat ~/.ssh/L-0.pub >> ~/.ssh/authorized_keys
cat ~/.ssh/L-1.pub >> ~/.ssh/authorized_keys
chmod 600 .ssh/authorized_keys                   # 赋予权限
ssh hadoop-master                                # 验证本机能无密码访问

1.3 关闭SELINUX
service iptables stop  
chkconfig iptables off 
vi /etc/selinux/config      # 关闭SELINUX后，需要重启服务器
-- 注释掉  
#SELINUX=enforcing  
#SELINUXTYPE=targeted  
-- 添加  
SELINUX=disabled