續上一篇文章：4. Hadoop集群搭建-克隆虛擬機/從機-基于CentOS7-【連載中】

前言

1. 請確保三臺主機可以互相Ping通
2. 盡量去做”快照“備份，以免發生故障后及時恢復，避免造成更大的損失，
3. 本次使用軟體：Xshell 6：藍奏下載，百度網盤下載Xshell6 - 提取碼: x2f3
4. Xshell使用技巧請參閱：Hadoop集群搭建-Xshell小技巧-基于CentOS7-【連載中】

正文

配置hosts檔案

1. Xshell連接三臺主機，步驟詳見：5.2 Hadoop集群搭建-Xshell新建會話連接圖解-基于CentOS7-【連載中】
2. 將三臺主機頁面設定為”瓷磚排列“，詳見：Hadoop集群搭建-Xshell小技巧-基于CentOS7-【連載中】
3. 在Master視窗輸入vim /etc/hosts（需要提前安裝vim彩色代碼命令：yum install -y vim）
4. 在最后一行輸入IP地址空格后輸入主機名，每個主機IP和主機名后要回車，也就是每個主機各占一行
   
5. 保存后發送到其他兩臺主機（需要輸入其他兩臺主機的密碼，需要輸入”yes“時請輸入”yes“）：scp /etc/hosts root@slave1:/etc/

[root@localhost ~]# scp /etc/hosts root@slave1:/etc/
The authenticity of host 'slave1 (192.168.***.***)' can't be established.
ECDSA key fingerprint is SHA256:1uOH6LWY9vqqbkbz93f6fbsHV/jKPEN8I0Zm37qb1ZU.
ECDSA key fingerprint is MD5:05:d2:b6:50:5f:32:f1:38:92:d9:c2:8e:df:42:e6:dc.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'slave1,192.168.**.***' (ECDSA) to the list of known hosts.
root@slave1's password: 
hosts                                                                                       100%  224   217.8KB/s   00:00    
[root@localhost ~]# scp /etc/hosts root@slave2:/etc/
The authenticity of host 'slave2 (192.168.**.***)' can't be established.
ECDSA key fingerprint is SHA256:1uOH6LWY9vqqbkbz93f6fbsHV/jKPEN8I0Zm37qb1ZU.
ECDSA key fingerprint is MD5:05:d2:b6:50:5f:32:f1:38:92:d9:c2:8e:df:42:e6:dc.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'slave2,192.168.***.****' (ECDSA) to the list of known hosts.
root@slave2's password: 
hosts                                                                                       100%  224   154.8KB/s   00:00    

配置免密

1. 三臺主機都要輸入：ssh-keygen -t rsa生成密鑰
   • 解釋：

Enter file in which to save the key (/root/.ssh/id_rsa):(/root/.ssh/id_rsa)
密鑰的生成路徑保存的位置為(/root/.ssh/id_rsa)，如果默認即回車，不默認即在冒號后方輸入自己的路徑
/root/.ssh/id_rsa already exists.
Overwrite (y/n)?出現這個是因為之前配置過（生成過）密鑰，詢問是否覆寫，y是覆寫，n是不覆寫，
Enter passphrase (empty for no passphrase):輸入密鑰的密碼，不需要直接回車
Enter same passphrase again:再次輸入相同的密碼（和上一步一樣，跳過，如果上一步輸入了密碼這一步就要輸入同樣的密碼，）
回車密鑰生成

2. 在撰寫欄中一路回車（建議參閱5.1 Hadoop集群搭建-Xshell小技巧-基于CentOS7-【連載中】后使用更流暢）：
   
3. 撰寫欄輸入（也就是三臺主機都要輸入）ssh-copy-id master將密鑰發送給master主機：

[root@localhost ~]# ssh-copy-id master
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
The authenticity of host 'master (192.168.**.***)' can't be established.
ECDSA key fingerprint is SHA256:1uOH6LWY9vqqbkbz93f6fbsHV/jKPEN8I0Zm37qb1ZU.
ECDSA key fingerprint is MD5:05:d2:b6:50:5f:32:f1:38:92:d9:c2:8e:df:42:e6:dc.
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@master's password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'master'"
and check to make sure that only the key(s) you wanted were added.

4. 轉到master輸入：cd /root/.ssh/使用ls查看該目錄下檔案：

[root@localhost ~]# cd /root/.ssh/
[root@localhost .ssh]# ls
authorized_keys  id_rsa  id_rsa.pub  known_hosts

5. 將authorized_keys檔案發送到其他兩臺從機：scp authorized_keys root@slave1:/root/.ssh/

[root@localhost .ssh]# scp authorized_keys root@slave1:/root/.ssh/
root@slave1's password: 
authorized_keys                                                                             100% 1224     1.0MB/s   00:00    
[root@localhost .ssh]# scp authorized_keys root@slave2:/root/.ssh/
root@slave2's password: 
authorized_keys                                                                             100% 1224     1.1MB/s   00:00

驗證免密是否成功

1. 在撰寫欄輸入：ssh master連接master查看是否需要密碼，如不需要即為配置免密成功（若詢問yes/no，請輸入yes）
2. 在撰寫欄輸入：exit退出連接
3. 之后再在撰寫欄輸入：ssh slave1連接slave1查看是否需要密碼，如不需要即為配置免密成功
4. 在撰寫欄輸入：exit退出連接（若詢問yes/no，請輸入yes）
5. 之后再在撰寫欄輸入：ssh slave2連接slave2查看是否需要密碼，如不需要即為配置免密成功
6. 在撰寫欄輸入：exit退出連接（若詢問yes/no，請輸入yes）

更改主機名

說白了，更改主機名就是為了讓用戶（自己）區分哪一臺是主機哪一臺是從機

臨時變更用戶名例：

[root@localhost ~]# hostname master
[root@localhost ~]# bash
[root@master ~]# 

永久變更用戶名例：

[root@localhost ~]# hostnamectl set-hostname slave1
[root@localhost ~]# bash
[root@slave1 ~]# 

相關文章：

5.1 Hadoop集群搭建-Xshell小技巧-基于CentOS7-【連載中】

5.2 Hadoop集群搭建-Xshell新建會話連接圖解-基于CentOS7-【連載中】

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