一般生产环境 Hadoop组件都是由hadoop用户来启动，首先需要配置hadoop用户ssh免密登录

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1.创建Hadoop用户

[root@hadoop000 ~]# useradd hadoop
[root@hadoop000 ~]# id hadoop
uid=1102(hadoop) gid=1102(hadoop) groups=1102(hadoop)
[root@hadoop000 ~]# passwd hadoop
Changing password for user hadoop.
New password: 
BAD PASSWORD: it is too simplistic/systematic
BAD PASSWORD: is too simple
Retype new password: 
passwd: all authentication tokens updated successfully.
#给hadoop sudo权限
[root@hadoop000 ~]# vi /etc/sudoers
hadoop ALL=(root) NOPASSWD:ALL

2.切换到hadoop用户 配置免密登录

[root@hadoop000 ~]# su - hadoop
#确保有ssh服务
[hadoop@hadoop000 ~]$ sudo service sshd status
openssh-daemon (pid  24823) is running...
[hadoop@hadoop000 ~]$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/hadoop/.ssh/id_rsa): 
Created directory '/home/hadoop/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/hadoop/.ssh/id_rsa.
Your public key has been saved in /home/hadoop/.ssh/id_rsa.pub.
The key fingerprint is:
bd:75:87:ca:44:2d:1f:de:b7:5e:a0:96:ac:b3:7e:01 hadoop@hadoop000
The key's randomart image is:
+--[ RSA 2048]----+
|                 |
|             .   |
|            o o  |
|         .E. + + |
|        S ..o * +|
|           *.= oo|
|          . B. ..|
|          .o. . .|
|         .++   . |
+-----------------+
[hadoop@hadoop000 ~]$ cd .ssh
[hadoop@hadoop000 .ssh]$ ll
total 8
-rw------- 1 hadoop hadoop 1675 May 17 14:59 id_rsa
-rw-r--r-- 1 hadoop hadoop  395 May 17 14:59 id_rsa.pub
[hadoop@hadoop000 .ssh]$ cat id_rsa.pub >> authorized_keys
[hadoop@hadoop000 .ssh]$ ll
total 12
-rw-rw-r-- 1 hadoop hadoop  395 May 17 14:59 authorized_keys
-rw------- 1 hadoop hadoop 1675 May 17 14:59 id_rsa
-rw-r--r-- 1 hadoop hadoop  395 May 17 14:59 id_rsa.pub
#authorized_keys权限必须为600
[hadoop@hadoop000 .ssh]$ chmod 600 authorized_keys
[hadoop@hadoop000 .ssh]$ ssh hadoop000 date
The authenticity of host 'hadoop000 (192.168.6.217)' can't be established.
RSA key fingerprint is 25:d9:d6:7e:fa:e0:a7:92:7c:06:76:5c:2b:19:bf:a3.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'hadoop000,192.168.6.217' (RSA) to the list of known hosts.
Thu May 17 15:00:28 CST 2018
[hadoop@hadoop000 .ssh]$ ssh hadoop000 date
Thu May 17 15:00:30 CST 2018

3.总结

hadoop用户配置ssh免密登录 authorized_keys权限必须改为600

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