最近做hadoop學習，按網上的資料照本宣科做的，發現死活搞不懂為啥在啟動和關閉namenode的時候都要輸入密碼。上網查詢半天都沒摸到頭腦，後來仔細研究了下ssh後才發現，原來是一直沒在namenode主機上加入ssh本地免驗證authorized_keys檔案，ssh 127.0.0.1 還是需要驗證密碼滴。。。。。很多網上的資料都沒專門指出這一步。特此留貼，做個紀念。


[[email protected] .ssh]$ start-all.sh
starting namenode, logging to /home/zzjlzx/hadoop/libexec/../logs/hadoop-zzjlzx-namenode-master.hadoop.com.out
slaves01.hadoop.com: 
slaves01.hadoop.com: starting datanode, logging to /home/zzjlzx/hadoop/logs/hadoop-zzjlzx-datanode-slaves01.hadoop.com.out
slaves02.hadoop.com: ssh: connect to host slaves02.hadoop.com port 22: No route to host
slaves03.hadoop.com: ssh: connect to host slaves03.hadoop.com port 22: No route to host

[email protected]'s password: 
master.hadoop.com: starting secondarynamenode, logging to /home/zzjlzx/hadoop/libexec/../logs/hadoop-zzjlzx-secondarynamenode-master.hadoop.com.out

1. ssh-keygen -t dsa -P '' -f ~/.ssh/id_dsa
2.cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys 
這兩步可以實現，本地 ssh localhost，配置完後，最好先 ssh 一下，這樣可以生成一些東西到 ~/.ssh/known_hosts 
如果是 偽分散式的，ssh 已經配置完成了。
有的系統，有時候還需要將~/.ssh/authorized_keys（這個也弄了半天，ssh對檔案的安全許可權也是有要求的。） 的許可權改為：600
完全分散式還需配置如下：
3. 將 Namenode 的 金鑰 複製自己的裡面，最好 雙向的都有，都可以互相ssh。
按一般的情況，現在已經配置完成了。
有時候，幾個節點 使用者名稱不一樣，Namenode 啟動其他節點的時候，預設用的自己下的 使用者名稱。
比如：Namenode 使用者名稱為 ：hadoop ，node1 使用者名稱為：user1
這樣是：ssh [email protected] 這樣登入 的，啟動時還會提示輸入密碼。
解決辦法：slaves 裡配置成：[email protected]
最好 各節點的使用者名稱一樣，Hadoop 裡 還有 安全認證，這樣好管理 。

hadoop叢集配置無密碼登陸範例：

1 生成私匙 id_rsa 與 公匙 id_rsa.pub 配置檔案 
[[email protected] ~]$ ssh-keygen -t rsa 
Generating public/private rsa key pair. 
Enter file in which to save the key (/home/hadoop/.ssh/id_rsa): 
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: 
d6:63:76:43:e2:5b:8e:85:ab:67:a2:7c:a6:8f:23:f9 [email protected] 

2 私匙 id_rsa 與 公匙 id_rsa.pub 配置檔案 
[[email protected] ~]$ ls .ssh/ 
authorized_keys  id_rsa  id_rsa.pub  known_hosts 
3 把公匙檔案上傳到namenode伺服器
$cd
$cd .ssh 
$cat id_dsa.pub >> authorized_keys
$ll
-rw-rw-r--. 1 zzjlzx zzjlzx  406 11月 29 01:01 authorized_keys
-rw-------. 1 zzjlzx zzjlzx 1675 11月 26 01:30 id_rsa
-rw-r--r--. 1 zzjlzx zzjlzx  406 11月 26 01:30 id_rsa.pub
-rw-r--r--. 1 zzjlzx zzjlzx 2440 11月 29 01:06 known_hosts
$chmod 600 authorized.keys
-rw-------. 1 zzjlzx zzjlzx  406 11月 29 01:01 authorized_keys
-rw-------. 1 zzjlzx zzjlzx 1675 11月 26 01:30 id_rsa
-rw-r--r--. 1 zzjlzx zzjlzx  406 11月 26 01:30 id_rsa.pub
-rw-r--r--. 1 zzjlzx zzjlzx 2440 11月 29 01:06 known_hosts
4 把公匙檔案上傳到datanode伺服器  [[email protected] ~]$ ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected] 
28 
[email protected]'s password: 
Now try logging into the machine, with "ssh '[email protected]'", and check in: 

  .ssh/authorized_keys 

to make sure we haven't added extra keys that you weren't expecting. 

[[email protected] ~]$ ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected] 
28 
[email protected]'s password: 
Now try logging into the machine, with "ssh '[email protected]'", and check in: 

  .ssh/authorized_keys 

to make sure we haven't added extra keys that you weren't expecting. 

[[email protected] ~]$ ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected] 
28 
[email protected]'s password: 
Now try logging into the machine, with "ssh '[email protected]'", and check in: 

  .ssh/authorized_keys 

to make sure we haven't added extra keys that you weren't expecting. 

[[email protected] ~]$ ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected] 
28 
[email protected]'s password: 
Now try logging into the machine, with "ssh '[email protected]'", and check in: 

  .ssh/authorized_keys 

to make sure we haven't added extra keys that you weren't expecting. 


5 驗證 
[[email protected] ~]$ ssh datanode1 
Last login: Thu Feb  2 09:01:16 2012 from 192.168.57.71 
[[email protected] ~]$ exit 
logout 

[[email protected] ~]$ ssh datanode2 
Last login: Thu Feb  2 09:01:18 2012 from 192.168.57.71 
[[email protected] ~]$ exit 
logout 

[[email protected] ~]$ ssh datanode3 
Last login: Thu Feb  2 09:01:20 2012 from 192.168.57.71 
[[email protected] ~]$ exit 
logout 

[[email protected] ~]$ ssh localhost 
Last login: Thu Feb  2 09:01:24 2012 from 192.168.57.71 
[[email protected] ~]$ exit 
logout 


參考：
http://dngood.blog.51cto.com/446195/775368
http://blog.csdn.net/tyj2788540/article/details/8191666